2007

Dr. Ahmed Shaabanru

Selected Topics

cutting Tools9lJ~/}varutJl{an«/arLwdJ~

Production Aids

AIN SHA1VIS UNIVERSITYFACUL'TY OF ENGINEERING4th Year production..

AGURE f The acceleration ofcutting tool material technologymeasured by permissible cuttingspeed (,..pm) for machining steet.

Introduction

into pr;octiaoYtartool material introduced

O~----~----~~----~-----L------~1800 '850 1900 1950 2000

150

T~L;t~i=

CeramicsIIT,CA' -0 ~.ted'"7 J carbide

IcBNICarbidet

I- Cast nonferrous alloy>

Success in metal cutting depends upon the selection of the proper cutting tool(material and geometry) for a given work material. A wide range of cutting toolmaterials is available with a variety of properties: performance capabilities, andcost. These include high carbon steels and low/medium alloy steels, high-speedsteels, cast cobalt alloys, cemented carbides, cast carbides, coated carbides.coated high-speed steels. ceramics, sintered polycrystaUine cubic boron nitride(CBN), sintered polycrystalline diamond, and single-crystal natural diamond.Figure f. presents a chronological rating of cutting tool materials, shewingthe rapid advances that have occurred in this field in the last two decades. Thetool materials arc rated by their permissible cutting speed in machining steel

Cutting Tool Materials

Vickers hardnessranges for various cutling tool mate­rials.

7654 e

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1. High hardness .2. Resistance to abrasion. wear. chipping of the cutting edge.3. High toughness (impact strength).4. High hOI hardness5. Strength10 resist bulk deformation.6. Good chemical stability (inertness or negligible affinity with the work

materia)).7. Adequate thermal properties.8. High elastic modulus (stiffness).9. Consistent tool life.10. Correctgeometry and surface finish .

. compares these properties for various cutting tool materials.compares various tool materials on the basis of hardness. the most critical

characteristic.Naturally, it would be most convenient if these materials were also easy to

fabricate. readily available, and inexpensive. since cutting tools are routinelyreplaced. Obviously many of the requirements conflict, and therefore. tool se­lection will always require trade-offs.

with greater performance reliability. Higher speed and/or removal rates usuallyimprove productivity. Predictable' tool performance is essential when machinetools are computer-controlled and have minimal operator interaction. Long toollife is desirable when machines are placed in cellular manufacturing systems.

The cutting tool is subjected 10 severe conditions. Tool temperatures of 1000°Celsius. severe friction. and high local stresses require that the tool have thesecharacteristics.

C4JttingTools for Machining

Knoop hardness scale - 1.000 Kplmm,

Diamond-natural/synthetic:

Sintered cubic boron nitride'-CBN

eVO·titanium carbide

S:nter-ed silicon car-bideeVO·titanium nitride carbon nitrideeVO·aluminum oxideeVO·chromium carbideOiffused layer-CVO·iron borideSiowed TiC-WC hard metals.Nitrided case of an a:1oy 5!~1Electro deposited hard ~hrome platedNitrided case of in u~lloy~ ;ttelHard~ned neelHardened and tetnJ:e~ sle'!1Iron

Cutting Tool Materials

Cutting Tools for Machining

3

High-Speed Steel. First introduced in 1900 by Taylor and White, high­speed steel is superior to tool steel in that it retains its cutting ability at tem­peratures up to IIO(tF. exhibiting good "red hardness." Compared with toolsteel, it can operate at about double the cutting speed with equal life. resultingin its name high-speed steel, often abbreviated HSS.

High-speed steels contain significant amounts of W, Mo, Co, V. and Crbesides Fe and C. W, Mo, Cr, and Co in the ferrite as a solid solution providestrengthening of the matrix beyond the tempering temperature, thus increasingthe hot hardness. Vanadium (V). along with W, Mo, and Cr. improves hardnessand wear resistance. Extensive solid solutioning of the matrix also ensures goodhardenability of these steels.

Tool Steels. Carbon steels and low/medium alloy steels, called 1001 steels.were once the most common cutting tool materials. Plain carbon steels of 0.90%to 1.30% carbon when hardened and tempered have good' hardness and strengthand adequate toughness and can be given a keen cutting edge. However. toolsteels lose hardness at temperatures above 400°F because of tempering

and have largely been replaced by other materials for metalcutting.

Low/medium aIloy steels have alloying elements such as Mo and Cr, whichimprove hardenability, and Wand Mo, which improve wear resistance. Thesetool materials also lose their hardness rapidly when heated to about their tem­pering temperature of 300o~50°F. and they have limited abrasion resistance.Consequently, low/medium alloy steels are used in relatively inexpensive cut­ting tools (such as drills, taps, dies. reamers, broaches, and chasers) for certainlow-speed cutting applications when the heat generated is not high enough toreduce their hardness significantly. High-speed steels. cemented carbides, andcoated tools are also used extensively to make these kinds of cutting tools.Though more expensive. they have longer tool life and improved performance.

In nearly all machining operations. cutting speed and feed are limited by thecapability of the tool material. Speeds and feeds must be kept low enough toprovide for an acceptable tool life. If not, the lime lost changing tools mayoutweigh the productivity gains from increasing cutting speed.

High-speed steels and cemented carbides. (coated and uncoated) are cUITe~ythe most extensively used tool materials. Diamond and CBN are used for specialapplications in which, ill spite of higher cost. their use is justified. Cast cobaltalloys are being phased out because of the high raw material cost and theincreasing availability of alternate 1001 materials. New ceramic materials arebeing introduced that will have significant impact on future manufacturingproductivity.

Tool requirements for other processes that use noncontacting tools, as inelectro-discharge machining (EDM) and electro-chemical machining (ECM). or110 tools at all (as in laser machining),

Development in carbide cutting-tool materials continues to yield new grades withapplication-specific combinations of properties. Technologies driving materialdevelopment are shrinking particle sizes and more complex compositions thatincreasingly use the non-tungsten carbide additions mentioned above.

••••••

Exceptional resistance to abrasionHigh modulus of elasticityChemical inertnessTorsional strength twice that ofHSSCompressive strength ,Toughness and resistance to impactWear resistance.

•

Carbide materials can be used to produce both inserts and solid round tools.Regardless of application, the materials have a combination of properties that allowthem to excel as cutting tool materials. These include:

Cemented carbide and cermet tools are made using PIM techniques. The blendedhard particles and binders are first pressed then sintered to produce inserts or solids

used to create round lools. (Sandvik Coromant)

C-eetod oatbfdoit do-M 11,1rft

Cemented carbide is a PIM product consisting of fine carbide particles distributedin a cobalt binder phase. Tungsten carbide (We) is the main carbide material used;others in use include titanium, tantalum, vanadium, chromium, and niobium carbides .111epercentage of hard particles in carbide tool materials can vary from about 60 to95%. By adjusting the type, size and concentration of particles, producers can tailorproperties to meet a wide variety of application requirements.

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Carbide has essentially replaced HSS in many applications, and is now thematerial of choice for more than half of all cutting tools produced worldwide. HSSaccounts for about 40%; the remaining 100/0 or so are made up of all other materials.

Cemented carbides are the most common cutting tool materials currently in use.Th'c chief advantage of carbide versus HSS is ability to cut at higher speeds: carbidetools cut 3 - 5 times faster than HSS.

,3. Carbides

5'

Cobalt enrichment is now so commonplace that manufacturers are using iteven in tools developed for high-speed finishing applications. The idea is to give anadded level of tool edge security. The process is also being carried a step further by

The cobalt-enriched layer, which maybe approximately 0.0005 - 0.001 tI (0.013 - 0.025 rom) thick, may contain cobaltconcentrations two to three times or more that of the bulk material. In the mostcommon enrichment process, the cobalt-enriched zone is produced by diffusion ofnitrogen, titanium and cobalt during sintering. Nitrogen can be obtained by replacingnitrides in the material with carbonitrides or by nitriding the "green" powder compactbefore sintering.

Developments inprocessingtechnology make possible another advance:cobalt enrichment of the surface layer of thematerial. By increasing the concentration ofcobalt binder phase near the surface,manufacturers can improve toughness therewhile maintaining hardness and wearresistance in other areas of the tcol.

Use of different types of carbides with a variety of properties also allows cuttingtool manufacturers to tailor tool materials. Additions of titanium carbide, tantalumcarbide, and niobium carbide are common. They tend to improve high-temperaturedeformation resistance and hot hardness, and increase resistance to chemical wear.Other additions, such as vanadium carbide and chromium carbide, tend to inhibitgrowth of the submicron grains during pressing and sintering.

In mechanical testing of a standard (grain size 2 - 311m)WC-8% Co carbideversus a subrnicron (grain size 0.3 - 1 urn) grade containing 11% Co, for example,transverse rupture strength increased from 2000. to 3000N/mm2 and compressivestrength increased from 5400 to 6000 N/mm2• In practice, high compressive strengthis important for machining materials that impose extremely high pressure on the tool. cutting edge, such as superalloys. .

Now researchers are exploring the potential benefits of "tano-phase" carbides,with particles on the order of 0.1 - 0.2 um in size. The finer particles again result insignificantly higher hardness for a given cobalt level. Interparticle distances in nano­phase carbides are so small that sintering temperatures can be lowered to inhibit graingrowth that may occur at higher processing temperatures. Nano-phase carbides· arebeing examined fer use as round tools, such as end mills fer exotic materials.

In the past few years, grain size of carbide powders used to produce tools hasshrunk from on the order of 10 urn to 1 urn. As in any P/M product, smaller grainsizes in carbides result in smaller voids and a denser finished material. Tools madewith submicron carbide materials have both higher hardness and toughness than toolsproduced using larger-grain materials.

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The Figure on the"rightshows some different formsof carbide tools used inturning process

Carbide is an artificial product and consists mainly of the hard materialstungsten carbide and other finest grind powders. This mixture will be sintered underextreme pressure and high temperatures until it becomes a solid object. Thereforecarbide cannot be compared to ferrous materials like steel. However, due to itsextreme hardness and finest graining which ensure a long endurance and clearedges of cut, it is also more brittle and fragile than steel. In this respect, carbide iscomparable to ceramics.

More specific grade recommendations can be obtained from data published bycarbide tool manufacturers, permitting a reasonable first-choice tool selection. Gradeoptimization, however, requires a complete analysis of cost, machining times, toollife, and other process parameters:

Also helping to narrow the range of grade possibilities for a specificapplication using carbide tools are ISO insert designations. The ISO c1assificationsystem provides a starting point for carbide tool selection by dividing grades intothree areas: P, for long-chipping materials such as most steels; M, for moredemanding materials such as stainless and heat-resistant alloys; and K for short­chipping materials such as cast irons, hardened steels, and many nonferrous materials.These designations combine these letterswith numbers indicating the suitability of thegrade for applications ranging from light finishing (01) to heavy roughing (50).

Selecting a carbide tool for a-specific application can be daunting given thenumber of grades available. Initial selection can be made based on workpiece materialcharacteristics"such as composition and hardness.

increasing the concentration of cobalt binder at the surface of carbide cullingtools improves toughness there while maintaining hardness and wear resistance inother areas. Cobalt enrichment is achieved by controlling sintering conditions.(Kennametal)

some researchers, who are working on changing cobalt concentration only in insertcomers.

And below is the ISO Classification of the carbide tools according to use.

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--.~--.....--C.Jassifiriation of THngf~t.enCarbides

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Below is the classification of the tungsten Carbides one of the most common types ofCarbides.

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Cutting Tools for Machin!

CoatedCarbide Tools. In cutting tools. material requirements at the surfaceof the tool need to be abrasion-resistant. hard. and chemically inert to preventthe tool and the work material from interacting chemically with each other duringcutting. A thin, chemically stable, hard refractory coating of TiC, TiN, or Al203accomplishes this objective. The bulk of the tool is a tough, shock-resistantcarbide which can withstand high-temperature plastic deformation and resistbreakage. The result is a composite tool as shown in Figure 6. Surfacetreatments for cutting tools are summarized in Table 4.To he effective. the coatings should be hard. refractory. chemically stable.

and chemically inert to shield the constituents of the tool and the workpiecefrom interacting chemically under cutting conditions. The coatings must be fine­grained. free of binders and porosity. Naturally, the coatings must be metal­lurgically bonded to the substrate. Interface coatings are graded to match theproperties of the coating and the substrate. The coatings must be thick enoughto prolong tool life but thin enough to prevent brittleness.

Coatings should have a low coefficient of friction so the chips do not adhereto the rake face. TiC-<:oatedtools were introduced in 1969. Coating materialsnow include single coatings of TiC, TiN, Al203, HfN, or HfC, and multiplecoatings of AI20) or TiN on top of AIP3 or TiC. Chemical vapor deposition(CVD) is the technique commonly used in the coating process. See Figure

7. The coatings are formed by chemical reactions that take place only on ornear the substrate. Like electroplating, chemical vapor deposition is' a processin which the deposit is built up atom by atom. It is therefore capable of producing

machining applications of super alloys. hard-chill cast iron, and high-strengthsteels. Because ceramics have poor thermal and mechanical shock resistance,interrupted cuts and interrupted application of coolants can lead to prematuretool failure. Edge chipping is usually the dominant mode of tool failure. Ce­ramics are not suitable for aluminum, titanium. and other materials that reactchemically with alumina-based ceramics. .

Exact properties depend upon materials, grain size, bonder content, volume fraction of eachconstituent, and method of fabrication.

TransverseHardness Rupture Compressive ModulusRockwell A (bend) Strength Strength of Elasticity (E)

or C (X tOl psi) (X W psi) (x 106 psi)

Carbide C 1-C4 90-95 RA 250-320 750-860 89-93Carbide C5-C8 91-93 R" 100-250 710-840 66-81High Speed Steel 86 RA 600 600--650 30Ceramic (oxide) 92-94 R... 100-125 400--650 5tH>OCast cobalt 46-Q2 Rc &0-120 220-335 40

, .:.' r :' Properties of Cutting Tool MaterIals Compared forCarbides, Ceramics, HSS. and Cast Cobalt

Can only be applied to steel.Process has embriulingeffect because of greaterhardness. Post-heattreatment needed for somealloys

Moderate production; piecesmust be fixtured, Part mustbe very clean. Coating doesnot diffuse into surface.which can affect impactproperties

Low friction coefficient. anti­galling. Corrosionresistance. High hardness

Prevents built-up edgeformalion in machining ofsteel

High production rates withbulk handling. High surfacehardness, Diffuses into thesteel surfaces. Simulatesstrain hardening

70-72 Rc0.0001 to0.100 in.

The part is the cathode in achromic acid solution;anode is lead. Hard chromeplating is the most commonprocess for wear resistance

ElectrolyticElectroplating

NitridingCaseHardening

No change inprior steelhardness

To 72 RcCase depth:

O'{)OOI in.to 0.100in.

HSS CUlling tools are oxidizedin a steam atmosphere at1000°

Steel surface is coated withnitride layer by use ofcyanide salt at 900°F to16{)O°F. or ammonia, gas orNz ions

Black Oxide Strictly for HSS tools

AdvantagesHardnessand Depth LimitationsMethodProcess

/

Al,OlAluminum oxide2nd layet-chemicalstabilitv at hightemperature-tests,sabrasive wear.

Titanium carbide (TiC)as first layer-strengthillIoj wear resistance

Surface Treatments for Cutting Tools

Triple-coated carbidetools provide resistance to wear andplastic deformation in machining ofsteel. abrasivewear in cast iron. andbuilt-up edge formation.

Titaniumr=:3--- nitride coating

+--Aluminumoxide-Znd layer

-f--- Titaniumcarbide- ht layer

Relativethicknessof coatings

Titanium carbide remains as the basic materialcovering the substrate for stlength <intiwearresistance. The ~econdlayer 's 31uoninumoxidewhich has proven chemical stability at higlltemperaWres and resists abrasive wear. Thethi(d layer is a thin coating of titanium nitrideto give (he insert 8 lOwer coefficient offriction and to reduceedge build-up.

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a) Catalytic conversion process, one-step process in which the catalyst,metal or alloy, aids in the transition of gBN to cBN simultaneously withthe formation of the compact

Known processes can be generally classified in four categories:

Methods of synthesis of cBN Polycrystals

Modifi-Coordinations No atoms! Lattice parameter DensityCation number unit cell a,nm c, nm g/cm

gBn 3 4 0.2504 0,661 2.29wBN 4 4 0.255 0,423 3.50cBN 4 8 0.3615 3.51

crystal chemical characteristics of differentmodifications of boron nitride [1]

Boron nitride exists in hexagonal graphite-like form (gBN), hexagonalwurtzite-like form and cubic zinc blend form or cubic nitride form. Under ambientconditions gBN is stable phase and wBN and cBN are metastable phases. The crystalchemical characteristics of various phases of boron nitride are given in table 1.

Boron nitride: crystal chemistry characteristics

During past decades cubic boron nitride (cBN) and wurtzite boron nitride(WBe) 'have received considerable attention. These dense modifications of boronnitride possess hardness approaching to diamond and thermal stability better than thatof diamond. They are chemically inert and do not react with iron. Superhard materialsmade on their base found wide application in many areas of metal cutting operations.

The compacts sintered from cBN or wBN powder have a polycrystallinecomposite structure either of cBN or cBN plus cutting tools made of this materialshow better service life in interrupted cutting of cast irons and hardened steels.

It is essential to have a proper understanding of this potential not only incutting applications, but due to their unique physical properties also in electronics.

4.·CBN

H',."

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II.

Hard phase BN compacts are of two general types: cluster compact andcomposite compact.

A cluster compact is defined as a cluster of abrasive crystals bonded togethereigher in a self-bonded relationship (1) or by means of some combination of betweenthe crystals (2) or by means of some combination of (1) and (2). For example,Borason [2], Elbor-R [3), Belbor [4], Hexanite-R [5], Amborit [6J, Kiborit [7J andother are those cluster compacts.

A composite compact is defined as a cluster compact bonded to the substratematerial, such as. cemented tungsten carbide or cemented titanium carbide. Theexamples ofsuch composite compacts are Compax BZN [8], DB 50 [9], Sumiboron[10], Wurzin [11], BPK [12], Composit 10D [14] and other.

The catalytic and bonding medium processes are generally disadvantageousbecause catalyst and bonding medium arc lower in hardness than cBN and retaining inthe resultant mass reduce the hardness and abrasive resistance of the masses.

The direct conversion process, which is theoretically and practically possible,has been found to have high losses in practice because it is difficult to achieveconsistently the sufficient number of crystal to crystal bonds distributed uniformlywith in the compact. Without this, the strength and density of the compact are lessthan it is necessary. And the no less so significant progress in this direction wasreached.

The considerable amount of high pressure sintering of cBN in presence ofvarious solvent catalyst has been done at the General Electric Company, and then atthe De Beers Company. Many different composites were created in the USSR. Thebest famous composites, which were created in "J.E." and De Beers are Borazon andAmborite. Aluminium has prived to very effective SOlvent-catalyst for manufacturingof cBN composites. The residual binder phases in the Borason and Amborite range ofproducts are aluminium nitride and aluminium diboride. The sintering of thesecomposites is done over a pressure range 5-7 GPa, at temperature range 1500-1200C.

Polycrystalline cBN, tool blanks consist of the layer 0.5- 0.7mm of cBN crystalsbonded to one another on a cemented carbide substrate. This composite structure isachieved t.hrough high temperature - high pressure process, resulting in an extremelyhigh wears and impact resistant product with very consistent physical properties fromblank to blank. As the cobalt in the WC-Co cemented carbide substrate melts at highpressure- high temperature process, it begins to infiltrate the voids in the compactpresented to cBN, thus completing the cementation process within the existing cBNcrystals.

Physical properties of hard and superhard materials are presented in table 2.

d) Direct conversion process, one-step process in which substantially puregBN is directly transformed to a cBN compact without the aid of thecatalyst and/or bonding medium.

b) Bonding medium process, two-step process in which the first stepcomprises the conversion of gBN to cBN and the second one comprisesthe formation of the compact from cleaned cBN crystals mixed with themetal alloy which aids in the bonding of the cBN to the compact.

c) Direct sintering process, a two-step process which is the same as theprocess (b) except that compact is formed without addition of metal oralloy to aid in bonding cBN crystals.

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12

Density, 10 kg/m 3.42 3.45 3.4-3.42 3.41-3.44Compressive strcngth,GPa 2.7 4.0-6.5 3.4-4.9 3.5-4.0Bending strength, GPa 4.0-1.2Fracture toughness, MPa m 4.2 13-17 15-17Knoop hardness, GPa 35 38 40.6-42.0 41.8Young's modulus, GPa 840 800 800 750-820Poisson's ratio, GPa 0.16 0.16CTE,IO k 1.8Thermal conductivity,w/m.k 60-80 100 70 25-30

Hexanite-R[14J

PHBN. [14,24}

. Belbor[4,14)

Elbor-RM[3,14)

Property

. Physical Properties of Superhard materials( direct synthesis)

Property WC+Co Syndite Amborit Kiborit Composite05ISO PCD25 PCBN PSBN PCBN

[9] [6] [6] [12,13J [14]

Density, 10 kg/m 14.7 3.86 3.42 3.4 4.3CompressiveStrength, GPa 4.5 7.61 2.73 2.9 23BendingStrength, GPa 2.7 I.l9 0.57 0,47FractureToughness, MPa m 10.8 8.89 6.30 10.5 6.7Knoop hardness,GPa 13 50 32 36 18.8Young'sModulus, GPa 620 810 680 880 620Poisson'sRadio,GPa 0.21 0.07 0.22 0.16 0.16CTE,lO K 5.4 4.6 4.9Thermal conduc-tivity, w/m.k 100 560 )00 100

Composites on the base wBN

/

Physical properties of Hard and Superhard materials

Polycrystalline dia­mond tools are carbides coated withdiamonds.

/

Cutting Tools for Machining

and has low chemical reactivity at the tool/chip interface. This material can beused to machine hard aerospace materials like Inconel 718 and Rene 95 as wellas chilled cast iron.

Cubic boron nitride, though not as hard as diamond, is less reactive withmaterials like hardened steels, hard-chill cast iron, and nickel-base and cobalt­base super alloys. CBN can be used efficiently and economically to machinesuch difficult-to-machine materials at higher speeds (@ 5 times) and with a

After the segmen tis brazed to thecarbide insert, theinsert is ready 'foruse..

Carbide insertswitl'l precisionpockets toaccept thesegm~t

Laserdicing dig:into~~ts

Braze Hoe

Compax blankiO.020" (0.57 mm) thickdiamcnd lay-er withcarbide substrata)

StandG.d tungstencarbide insert

Raw material fromsiotedng andt01npactil1l}

PQlycrystaldiamond

14

The chief limitation of diamond cutting tool materials=whether pen or thick­film-vis their inability to machine ferrous alloys. Caused by a chemical reactionbetween the tool and the work material, this limitation led to development of the othermain class of superhard cutting tool materials, cubic boron nitride (CBN). CBN tooluse is currently growing at a rate of 10 - 15% annually, driven mainly by increaseduse of hard turning.

Thick-film diamond competes with PCD for use in general machiningapplications. Because the material is pure diamond, it possesses advantages' over PCDin terms of greater hardness, wear resistance, and thermal stability. Thick-filmdiamond tooling is said to demonstrate tool life two to three times that of peD insome applications.

Thick-film CVD diamond is grO\\111 in sheets that are laser-cutinto tips. The tipsare then brazed to a carbide substrate in a process similar to that used to produce reDtools.

There are two types of eVD diamond tooling: thin coatings typically deposited ona carbide substrate, and thicker, free-standing diamond layers up to 1nun thick. Thin­film CVD diamond coatings will be covered in Part 2 of this series of articles.

Another diamond product developed more recently is chemical vapor deposited(CVD) diamond: The material is produced when carbon-based gases and hydrogen aredisassociated at high temperature, depositing diamond onto a substrate. The depositedmaterial is fully dense, polycrystalline diamond that is free of metal binders and thushas hardness and thermal stability near that of natural diamond.

Today, many types of diamond materials are available for cutting toolapplications, These include diamond coatings deposited by various methods, as wellas-thick-film diamond, which is a thick (250 Jim - 1mm) layer of pure diamondbrazed to a carbide substrate.

5.-Diamond

Cutting tool materials based on silicon nitride include fully dense Si3N4 andSiAION materials, which are solid solutions of alumina in ShN4• Fully dense ShN4can have fracture toughness nearly as high as cemented carbides, high strength, and alow coefficient of thermal expansion that results invery good thermal shockresistance. Tools made with thismaterial are excellent for turning gray cast iron, and .are also used for milling and other interrupted-cut operations on gray iron. Coolantcan be used for turning applications.

The whiskers improve properties by essentially locking into the ceramic matrix,and by virtue of their extremely high tensile strength-on the order of 1,000,000 psi(6.9 GPa). About 100 times longer than they are wide, the randomly oriented whiskerscan be broken, but it takes tremendous force to pull them out of the matrix. Whiskeredceramics are applicable to a variety of workpiece materials oyer a hardness range ofabout Rc 50 - 65.

Alumina reinforced with SiC whiskers is the toughest and most resistant tothermal shock of the Ah03-based ceramics. Unlike other such materials, it can be runwith coolant. High-speed finishing of nickel-base superalloys is a typical applicationfor whisker-reinforced ceramic cutting tools.

Alumina-based cutting tool compositions include additions of zirconia (Zr02),titanium carbide, titanium nitride, or silicon carbide (SiC) whiskers. Alumina-zirconia("white ceramic") contains up to 10% Zro2 for toughness. White ceramic materialsare effective in steel finishing operations. Alumina with additions of up to 40% TiC isespecially abrasion-resistant and is used for machining chilled cast irons and hardenedsteels.

The key to successful application of ceramic cutting tools is to remember that theycan take far more heat than carbides-they soften at temperatures in the range of4000°F (2200°C), versus about 1600°F (870°C) for carbide materials. Ceramic toolsmake very hard work materials machinable essentially by cutting at speeds thatgenerate enough heat to raise the workpiece temperature to the vicinity of 1800°F.Cutting speed generates the heat needed for ceramic tools to work properly.

Ceramic cutting tools have found application principally in turning and millingcast irons and superalloys and in finishing hardened steels. These are applicationswhere ceramics based on aluminum oxide (Ah03) and silicon nitride (SiJN4) cansignificantly outperform carbide tools.

Ceramics are hard and nonreactive=two properties that make them attractive ascutting tool materials. This. combination of hardness=even at extreme temperatures­and chemical inertness means that ceramics can run hotter and longer with less wearthan competing materials. They have long tool lives and can machine at high cuttingspeeds with very high metal removal rates in the right application.

6. Ceramics

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Gell8Tallumlng of cast ilon.A fut1harImprO¥emen!InAAlmlnlumOldeJebased ceramicO1!ertnlllncrnsed IeSlslancato Wl!3rand deplh orwl nolthlng

Tube seat1lng8nd generallumlng ofnstlron.

Composed ofpure a!umlna ¥tiIh .ddilion ofZi~orJato ImproveIDughness.

Dense amI On6's1rvcture resulting InImprbv9d 'W!l3(luistantean~~bllitt.

IGeneralbJmlno.boring and .Ilrom1ngcf

casilron.Aluminium OJddebaHd ceramic

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Wluminium Oxide Grades

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Oxide Materials Silicon BasedCRYSTAl. Ceramic PSZ Single Crystals Nitride CarbideProperty P5Z - CubiczrO:- YzO, Y·PSZ Mg-PSZ Zirconia Soppl'ire SbN4 SiC

9-mole%} AbOl

Density, !1l'lIcm' 6.08 6.05 5.75 5.8 3.96 3.2 3.2Bending strenGth. 600- 500-MPa @20°C 500-1600 1000 BOO 200-400 300-500 900 600

@1200" C . 500 500@1400· C 700 - .

Crock fESistonce, 8-14 7·12 7·12 2-4 3-4 5-7 3·4K1CMPa.mV2

Micro hordnes<.>.HPa 12-15 '13 11 12·16 19 16 28

Coef. Of frictionOn Steel 0.04 0.15CMAlloy 0.08 -IT 1r1'C-' 9.3-'1.4 10.4 10.48 10 - 11 10.48 12-16 4.2

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Comparisonphysical and mechanical parametersof high-strengthstructural non-metallic materials

SiAION materials and whisker-reinforced ceramics may also react with certainworkpiece materials. This can be minimized by coating SiAlON tools with TiN oranother coating material.

SiAIONs are typically more chemically stable than ShN4 but not quite as tough OJ'

resistant to thermal shock. They are mainly used in rough turning of nickel-based .superalloys.

350

11-

,00 300250

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150 200TIme (rrinutes)

O.OO4~ood of life crlte-tlon

• ~coaIinO----+- + OLe coating

• nAJN coating

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r- 5..-~~ 4...•~ aJllI:..II:

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Graphite machining wear comparisonsri cVO diamond toot vs. Ole and TtA1Ncoated tools

Square ~r.dmill. 2-ftutes. 114x 314X 2-112 In., at 9000 1J)m. .002 fpr •. 050" DOC

A Chart to comparehardness of material withtemperature change

lOCI!\_l

~.{,

fG -.~

.t,fl -.c;-,... :J:~ ,_.

-[ ~ 15-

~~j 10 ~.:

-i(os .,.

t.ll

...,0

At the end we can notice the development and improvement of many cuttingmaterial. Now we are left with simple tables and charts that would clarify thedifferences between these materials.

c

7. Conclusion

."c.2Q...,IJ><UJ

<:CEEoIJ

i:'.,>eeou

"2u-=9

1

I·A

c:.:2d<.J.;:.0:ISU.

-0ooc:Il

6>v"0oo1>1)

"

I II II I

]~eU

-oII)CI)

tCI)c.o....0..

jiijen

t'\

Fig. 1 . Types of form toolss(a) circular form tool with zero rake; (b) circular form tool wlth positive rake; (c) hettcat circularform tool; (d) radial-Iced flat form tool; (e) tangenllal (skiving) form tool; (f) circular form 1001fLIUh a swivelled axis; (g) end form fool

(b)(a)

~- i(

1 -1. Types of Form ToolsA form tool is one in which the cutting edge is of a shape that pro­

duces the desired contour on the workpiece in the turning operat ion.The use of a form tool ensures a high output, uniform contour of allthe workpieces and accurate dimensions. I t is commonly applied inlarge-lot .and mass production. .

1 Form tools can be classified: (1) according to their type as circular"1 (Fig. 1 :Q, b. c, and f), flat (Fig. L d and e) and end form tools\I,

FORM TOOLS

20

(Fig. 1 .g); (2) according to the setting of Rat tools in respect to thlworkpiece as tools with a radial cutting edge (Fig .. - ;d) and tangen­t ial (skiving) tools (Fig. .e): (3) according to the position of th(tool axis as tools with the axis parallel to the workpiece ax i:(Fig. 1 .a, b, and c) and those with an angular location of the ax i:or mounting surfaces. (Fig. 1 :j); and (4) according to the elementsof the contoured surface (on the tool) as circular tools with annularelements (Fig. t ·a and bL circular with helical elements (Fig. I c),and flat wi th flat elements (Fig .. 1 d and e).

Form tools (circular and fiat) with the axis or mounting surfaceat an angle to the workpiece axis (Fig, I . l) are seldom used, owingto their. complex manufacture, and then only when the shape of theworkpiece contour is such (for instance, on section ab) that tools witha parallel axis cannot be employed.

1\10st form tools are made of high-speed steel, but cemented carbidesare being more and more extensively used for th is purpose.

The plast ifled and compacted (but as yet unsintered) cementedcarbide can be easily machined with ordinary carbide-tipped tools.The blanks obtained after turning and cutting off have dimensions25 to 30 per cent larger than those required on the finished tool con­tour. These blanks are then sintered and brazed to a shank or are' heldmechanically on the holder of the form tool (Fig. 2. ~'.)..

The use of. contoured cemented-carbide tips for form tools enablesthe productivity to be raised by 30 to 40 per cent (in comparison withhigh -speed steel Iorrn tools). .

A. form tool should have the proper rake and relief angles so thatthe metal is 'cut under sufficiently advantageous conditions. Rakeangles are listed in Table l' for the Iorni turning of various mate­ri als,

Fig. I Carbide-tipped circulcform tool:1 - body; 2 - contoured up; 3-backing member

3 2 f

DESlGN OF SINGLE-POINT LATHE TOOLS

!~.

21

io- or 15°,The outside diameter of a circular form tool is determined in accord­

ance with the height of the profile to be turned. A graphical construc­tion {Fig. 3·) is recommended for this purpose in designing positiverake form tools (1'>0), which is done as follows. About axis 0 of theworkpiece we draw two concentric circles with radii equal to the maxi­mum' and minimum radii of the contour to be turned. Through point A,at the angle y. we draw a line representing the trace of the planeground to produce the tool face. From the same point A we draw a se­cond line at an angle equal to the relief angle <x. At the distance kfrom the point of contact B we draw a line perpendicular to 001,

The distance k is the minimum amount that will permit chip disposa-lfrom the tool face. From the point of intersection C of the verticalline and the Iine of the tool face, we draw a line bisecting angle 00;the point of intersection of this bisector and the line drawn at theangle a is the point being sought-the centre O2 of the circular tool.The distance k is taken from 3 to 12 mm depending upon the chipthickness and the amount of 'Chips to be cut. The tool centre O2 beingknown, .it is possible to draw a circle of a radius R and to determineall the other dimensions graphically. To determine the diameter

The relief angle a depends upon the type of form tool. On circularform tools a=10° to 12°; on fiat form tools Ct= 120 fo 15°. On formtools intended for relieving form milling cutters, the relief angle amay reach 25° or 30°. Such a large value is necessary because angle j.t

of inclination of the path of relative motion may reach

I Mechanical properties of the workI Material

materialY. degrees

[- <Jt, kgf/mm t Bhri

1I -- Aluminium, copper 20 to 25!I Bronze, _leaded brass 0 to 5J '•.r: Mild steel up to 50 up to 150 25{- Medium-hard steel from 50 to 80 150 to 235 20 to 25~ Hard steel » 80 to 100 235 to 290 12 to 20,

Very hard steel » 100 to 120 290 to 350 8 to 12'/- Soft cast iron up to 150 15'.1 Hard cast iron 150 to 200 12~ Very hard cast iron 200 to 250 8~. -

'- ----------~---------.----------------------~----------Table 1 Rake Anglos for Form Turning Various MaterIals

. FORM TOOLS

,...ff -

!) ,);d:~ .Jt'S'

~~"--"_4--+#--- i.·Oj

• ........ ~.- .... ~ ....... - ..... - ...... &.... ............_,__. " , -- _.. . -. "'~_.'''''''''''----~, ,-.

1 -2. Methods of Determining the Profile'. of Form Tools. Shown in Fig. 5 is the graphical method of determining the pro­file of a circular form tool. First the profile of.the workpiece is drawn.in the lower left-hand corner of the drawing. Next we project the basicpoints of the profile on axis 1-/, drawn perpendicular to the work­piece axis. The projected points are I', 2', 3', etc. From point 01as the centre we describe circles corresponding to the radii r1, r2,.r I, etc. .

of the graphical or analytical methods' that have been devised forthis purpose. .'The graph ical method is 'simple and straightforward but has certain

inaccuracies inherent in all graphical constructions. The analyticalmethod, on the contrary, enables the dimensions to be determinedwith any degree of accuracy. A drawback of ·the last method is thecomplicated calculations required, especially Jn the case of a curvili­near profile.

Fig.Jr . Clamping a circular form fool inthe holder

12. FOPM TOOLS

t------____ -_---Rwi

Z= Length of form measured on the tool face/'

X == Depth of form measured rpendicular to the tool flank~ R,

Sec. Rwi R .2 fw rw sin 'Y (rw sin}').! fw COS 'Y z, Xr=Z, COS (o+y)WI

1 Rwl RwJl. z.. X1=ZI cos (a+y)2 Rw2 Rw2l. Z2 X2=Z2 cos (a+y)

RW31.M

3 RW3 ~ ~ ~ Z3 X3=Z3 cos (a+y)RW41. = = r:Il

4 RW4 ~ .- .- 0 Z4 ~=Z4 cos «(1+Y);. rn r:Il C)

5 Rw5 RW51. ~ ~ ~ Zs Xs=Zs cos «(1+Y)

R"'162~ ;.

6 Rw6 '-" Z6 ~=4 cos «(1+Y)7

Z == ~ Rw2 - (r., sin y)2 - fw cos 'YX == Z cos (a+y)

a ,-I

Analytical determinationflat form tool

.'.

I \·t~-"I . 110 \.-, -t ): '-.._-,11""It ,,-...·1 ?-

1+~ ~

?- ?- <;»

---l + tilt> rn 0-f~ 0 tS (.)

1~

C,) <;»

J rfJ. ~1 f 0i I 0 N

?- N~ N

~I

1 ~ ~ N..,...( N~

CI)

~ N C'l

1 J I +~ N N

--.J~

o N:~

~ ,._...+ I I

'-.)~ ~N

\_. II II- II . tl! \J' N o~ ~$...1

~ 25~~'l~

~~... 'r·.. ·1'

.. '

Z6

o ......... ~ ~ "5 II') \0H ~ ~

o ()~I J-c ~ H

~

I I J I I I

cZ ~ ~ cZ ~ rlII II II II II II II~

......... ~ ~ ..q- II') \0

~ >< ~ >< >< ~._ - ~ ~ .._;t II') \0o~

()~

o o oH l-4 J-c H ~

I"..-.._ ~ ,-,. ~ f ,,-..., t?- f + + is"-t Ies d

~~ t:S

II

......._" '-'" ......_., <:» ....__.. <;»1J) til {/) til til 1J) til0 0 0 0 0 0 0<.) o o o o o C)..... ......... . ~ ~ ~ IJ') \0N N N N N N N(.)

~ ~o

~c» u

~ ~ ~ ~N C'l N M N N N

~

~

cZ ._-

cZ cZN

,.... N ~ N IJ') \0N N N N

?- ?-en. r/)

0 0<.) u~ ;!H

N ~~ ~

~ b..-( ..-(Vl tr:

~~H

<:» <:»

~ b...... .~V) tI.l~ .I' ~H H

~ 3H H

N NNN ~f"'l ~-.::t ~ N\O.~ - II')

r1 r1 J r1 J r1~ ._.-J f"'l JJ \0

J r1 J r1C,)

~ r-d) ~ N ~ V) \.0 00tI)

In '"• •ex IZ

.21-

" : \. \

. \ . \

. \ ~\ \.. '.

iI

\;

/

t.'56fs....- _- ~

_ i.

,- '

•- ~-I ~;.',

i·

TT~

l

1

- --- /-

-001 in positionerpendicular to theolfiank

~x.of'W. Corn').

Cutting "toolin £u.ll depth

W.P invertica.l

-----+-----++-+l-!I-H-r---""1v dirction

Flat f<>~'m'toolL Gra.phical met:4od

--~------~--~-4----~--J---+----hilC-i--t---t--u

-,\.\\\\/

I/

/

\.\....j

\\).~

~

~\.,\)

~e ~

tS-J

~

~-,j

./

----··-·-~-+-I7t"11

L~~~------41~~IT-

I

I

(J'or'-----

Fig. 161. Grinding the tool face in. sharpeningform tools:(a) {fat form tool; (b) circular form 1001

Fig. 160. Circular [orm tool

R,=50

12. FORM TOOLS232

31

18-0709

Fig. '128. Examples of mechanical fixing of hard-metal tips

At present, tipped cutting tools are so widely used in machine­building industry that they have ousted not only many tools madefrom carbon tool steel but supersede to a great extent the tools madefrom high-speed steel. This is especially true for turning tools andvarious cutters and drills designed for automatic machines. Hard­metal tips are different in form and size; they may be prismatic,polyhedral, round and of more intricate forms. The most simpletipped cutting tools are made up, of a holder or body with one orseveral hard-metal tips which are brazed in special seats.On choosing the position of a tip, it is necessary to ensure a pos­

sible greater number of regrindings of the tool with the purpose ofbetter utilization of expensive hard metal and making a strong andreliable construction allowing workpieces to be machined at highcutting duties. I n addition, the tip' should be so positioned that,

, Tool Tipping

r-i

I..+;

""'"''r x ,

,

OLS'- - f- ,

~~~1ir

- ~

~~:~- r.'f

32.Cutting edge angles of diamond cutters

(a) cutter with trimming r~~P.t· fh) with t"'rnrni",..,. ....A_~ :_ ....._ • __ • ••..•

(c)(b)(a)

Diamond cutters(a) diamond fixed by brazing; (b) mechanically

fixed

(a)I ~tJo

<1--

Form cutters(a) bar-shape; (b) prismatic; (c) round-nose

/

33

with V in surface tr1per minute and D in ".,,,..,

-I)

Fundamentals of the Drilling Process. The process of drilling creates.two chips. A conventional two-flute drill, with drill of diameter D, has twoprincipal cutting edges rotating./at an rpm of N and feeding axially. The rpm ofthe drill is established by the selected cutting velocity. V, where

1()tI~VtV =-­

'rrD

In manufacturing, it is probable that more holes are produced than any other.shape, and a large proportion of these are made by drilling. Consequently.drilling is a very important process. Although drilling appears to be a relativelysimple process. certain aspects of it cause considerable difficulty. Most drillingis done with a tool having two cutting edges. These edges are at the end of arelatively flexible tool. Cutting action takes place inside the workpiece. Theonly exit for the chips is the hole that is filled by the drill. Friction results inheat that is additional to that due to chip formation. The counterflow of thechips makes lubrication and cooling difficult.

In recent years, new drill point geometries and TiN coatings have resulted inimproved hole accuracy. longer life. self-centering action, and increased-feed­rate capabilities. However. virtually 99% of the drills manufactured have theconventional point and geometry shown in Figure -I. If the drill is reground.the original drill geometry may be lost. Drill accuracy arid precision will alsodepend upon the drilling machine tool. [he workholding device. the drill holder.and the surface of the workpiece. Poor surface conditions {sand pockets and/orchilled hard spots on castings. hard oxide scale on hot rolled metal) can accel­erate early tool failure and degrade the hole-drilling process.

Introduction

Drilling and Related~tH=.•o=,=e-=M=:a=:k:=in=9=p=. r=o=ce=s=s=e=s~~~::==-",J

rf!~ .~~~$~F--------------------------------------------------~--------------

34

Counter-boring

T

II

I,II

I

FIGURE -6 Drills for boring anddrilling deep holes.

FIGURE -1 Nomenclaturegeometry of conventional twisl

/

Rake angleMgCItiveSolid boring

Width of cuttingrecess

Chip-breaker drain or groove

Mtaturing padL~tc+--.Ci~lelandormargin-J-- --- -

Chip mouth

Supporting padLeading ramp ~

Radial cutting clearance-

angle

Outer cornercomer

Bodydiametercle;;rarn:e

---------------------BodV------------------~1--------- Flute length ----------~

Drilling and Related Hole-Making Proce:

35

feeds and speeds used, and whether the tool or the workpiece is rotated orcounter-rotated .

Two-flute drills arc available that have holes extending throughout the lengthof each land to permit coolant to be supplied, under pressure, to the pointadjacent 10 each cutting edge. These are helpful in providing cooling and alsoin promoting chip removal from the hole in drilling to moderate depths. Theyrequire special fittings through which the coolant can be supplied to the rotatingdrill and-areused primarilyon automatic and semiautomatic machines. See Table- I for comparison of drilling processes.Larger holes in thin material may be made with a hole cutter, shown in Figure·7, whereby the main hole is produced by the thin-walled, multiple tooth

cutter with saw teeth. Hole cutters are often called hole saws.When starting to drill a hole, a drill can deflect rather easily because of the

"walking" action of the chisel point. Consequently, to assure that a hole isstarted accurately. a center drill and countersink, illustrated in Figure .-8, isused prior to a regular chisel-point twist drill. The center drill and countersinkhas a short, straight drill section extending beyond a 60-degree taper portion.The heavy, short body provides rigidity so that a hole can be started with littlepossibility of tool deflection. The hole should be drilled only partway up on thetapered section of countersink. The conical portion of the hole serves to guidethe drill being used to make the main hole. Combination center drills are madein four sizes to provide the proper-size starting hole for any drill. If the drill issufficiently large in diameter, or if it is sufficiently short, satisfactory accuracyoften may be obtained without center drilling. Special drill holders are availablethat penn it drills to be held with only a very short length protruding.

Because of its flexibility. a drill may drift off centerline during drilling. Theuse of a center (start) drill helps to assure that a drill starts drilling at the desiredlocation. Nonhomogcneities in the workpiece and imperfect drill geometries mayalso cause the hole 10 be oversize or off-line. If accuracy in these respects isdesired, it is necessary to follow center drilling and drilling by boring andreaming, as illustrated in Figure 244. Boring trues the hole alignment, whereasreaming brings the hole to accurate size and improves the surface finish.

FIGURE ·8 Combinationcenterdrill and countersink. (CourtesyChi­cagO-Latrobe Twist Drill Works,)

FIGURE ·7 Hole cutler usedforthin sheets. (Courtesy Armstrong­Blum ManufacturingCompany.)

.Ire and'fj,' tJrift.;

Diameter [rnrn]25 to 150 18 to 60

Hole depth/diameter rationo minimum !>40 501O( vertical)>1000horizonl<l1) >50

SolidTrepanning Boring Drill

42 to 250 1210200

10 1100 100

>100 >100

EjectorDrill

SpadeDriU

., Twist Gun•~ Type or Drill Drill Drill

r,ypical size range 0.5 to 50 1.41025~~'inimum practical no minimum <IS .: 5-10 100D>mmon maxrmum';

(Ultimate >50 200<

1 Comparison of Drilling Processes

Material Removal Processes

Typos of reamers~~iii.,

l

Types of counterbores~ 't:::s

(f)

Types of special-purpose drills

A-A At-

1 JL J

Ir"

f i'iI

;r';f -,

(6) ,.& Taper

~~~~~ l 4

l I

(d)

(6)

Front face

(c)" .

(0)

a, UCIIIS, Lounterbores and Reamers

., -.: .J

~a- II. I I I

L

i;!.! : .-:: = t ;' -:;- .i --.:t ~: - -;:

I r:i ' -

,-. ~tj = c:5-~-:)=

--~ -: ..01"'--

L",-,l-----·0'=I ; 0

c--J 0o·

I, r C"T,j \

o

;?- o- _ -.J

......'-------<,

'-,' "~-;-==., ~-l .: " ~t: -:- . , ,----------T. 'r - QII ! I! - i, I I I .

__ ! I I !, I' I

~-.!~-- fl' ; I i!O '-~ ;, D:: 3:,5-0,011 I~~~ ,I I_j; I

II

I

t.·,

"

_i

"f'!

t.I

'.'~

FIGURE '. 10 Special-purposesubland drill (above), and some 01Itoperations possible with such drillstbelow) .

FIGURE 9 Steps required tolain a hole that is accurate as to siand aligned on center.

/

38

DTiil .nd o-tn. cou".t~rsinkc"''''''tf a"o c:oonur-bon!

O,Ul.ncID,i.ltmultiple Muhip~ d/ill DfiUanddi.rnete-r-t ccwntlnink cooJl'\teninlc

..NS c::ou..",..-bo ....

Slep " Final sizing wi1h reamerSlep 2 Drilling(::::::n::: dJSlep 3 Truing hole wilh boringcullerStep 1 Centering and co~'nter·sinl<ing

Drilling and Related Hole-Making Processes

G1.-< (l

(b)I. i,,. ,

C::J

<;1__ .....:l:...___ ___.L,_

(a)r

CI

b r = 0.8 Th ::: O. 8x 0 .025 !:' 0.02 mm

'1' t: = ; I::. r = O. 00 7 rnm

dr = (dh+ Ar)_ T = (20 + 0,02)_0.007r:: (20.02) - 0.007

A = 0.25' mmr

ExampleFor ahole ~ 20 H7 in steel

dh = 20 mm T ::::: + 0.025 mmh

d """ dh - Ar = 20- 0.25 - 19.75 mm1

3:::Tr

allow for a sutisfactory reamer life1

6r

The upper limit of the reamer diameter is taken nearest to the upper

limit of the hole dimeter ~o allow for a reasonable working life of

the reamer. However to account for the Possible reamer-run out, the

upper limit of the reamer is taken 20% less than the, upper Limit of

the l~-oie. -This is expressed as f o Lkows ;

l:,. r = 0.8 Th'l'hereamer tolerance is taken much Le ss -than that of the hole to

:e

The reamer size (d r) is give:. by

d :: (dh + Dr)_-- r T r

A = machining allowance which depends on the workpie~ematerial and the hole size (dh) t table -(1)

Reamer size:

Tbe initial hole diameter before r eam i nq (d1) is obtained as follows:

d1 ::::dh - A

The required hole size after reaming is usually given in the for

H· H + Tnd. 7 or dn, 8 as ',.;ellas d.n n

r e a.a inq :Initial hole diameter before

the rcamer and for setting

the size of adjustable and

expansion reamers.

L

I u; Ir....- :

1II-I--J ii

for monu[a cluring

The r e arner Size i s c a Lc u La t e d f r om the required hole sizetaking into consideration the wear of the reamer teeth and the

probable run out of the reamer. The obtained reamer size i~ used

._-------------------------------- -

/'initial hole Size and Reamer SizeDetermination of the

..;,':" '

'-'_" ....~

t,o

cil = 2~'- 0.25 = 19.75 mm

before reaming is

dl = Hole diameter before reaming == dh - ~achining allowance (A}

Example: for ID20 H7 the hole diameter in steel W.Pi!,~-,:, ~jl

;1:::..,;p~I :~-

for a workpiece material

A rMachining allowance (diametral)Hole diam

dh (mm)

IUp to 5 0.1 m~ 0.1 - 0.2

5-12 0.15 mm 0.3

12-18 0.20 .mm 0.4I

I 18-30 0.25 mm 0.5, -,

30-50 0.30 mm 0.6 ,50-60 0.40 mtn O.B

60-80 0.50 rom 1

IL1hie(i); Mllchining allo.wance for reamers

To dete~min~ the hole size befo[Ereaming

Ir~Il?

I~~~~v.t!~--------------~------------------------------------------~---~-----!(

i

r--------·------Total broachlength---------SectionA·A"

o .1

Cuttingmotion

P- pilchof tet!tho - depthof teeth WAPIl - land behiod cutting edge (O.25?)R - radiusof gullet :.25P)n - hook angleor rakeangle., - t.:ackoffa"qleOr clearanceangle

RPT- risepeo- tooth(chipload)~ f,J

FIGURE .-1 Basic shapeandnomenclaturefor conventionalpull(hole) broach.Section A-A' showsthe cross section of a roughingtooth.

Broaching

Broaching

",,

-111

I~:~~-I~i~I~«~'-.:~============~======~====~====~~_i;

i ~, ~

-I: The process of broaching. as illustrated in figure I, is one of the mOSI,.? productive of the basic machining processes. Broaching competes economically

/' with milling and boring and is capable of producing precision-machined sur­i faces. Broaching is similar to shaping, bUI a broach finishes an entire surfacei in a single pass whereas a shaper requires many strokes. Broaches are used in

r ....production to finish holes, splines, and flat surfaces. Feed per tooth in broachingis the change in height of successive teeth. Broaching is similar to sawing exceptthat the saw makes many passes through the cut. The heart of this process lies

/'

I,,,i~.~11

4'J..

.:-!eI':-\. ,"'- .;.; :-";' .' Ii. . .,...j'.... "', < .'i· 'f:, .t,; if,, , "~ -

Finishing teeth

FIGURE -4 Rotor or jump tootlbroach design.

Broaching. Sawing. Filing

Broach Design. Figure -I shows the principal components of i:! broachand the shape and arrangement of the teeth. Each tooth is essentially a single­edge cutting tool. arranged much like the teeth on a saw except for the step.which determines the depth cut by each tooth. The depth of cut varies fromabout 0.006 in. for roughing teeth in machining free-cutting steel to a minimum0.001 in. for finishing teeth. The exact amount depends on several factors. Too­large cuts impose undue stresses on the teeth and the work: too-small cuts resultin rubbing rather than cutting action. The strength and ductility of the metalbeing cut are the primary factors.

Where it is desirable for each tooth to take a deep cut. as in broaching castings. or forgings that have a hard. abrasive surface layer. rotor-cut or jump-cut toothdesign. shown in Figure -4. may be used. In this design. two or three teethin succession have the same diameter. or height, but each tooth of the group isnotched or cut away so that it cuts only a portion of the circumference or width.This permits deeper but narrower cuts by each tooth without increasing the totalload per tooth. This tooth design also reduces the forces andthe power require­ments.

Tooth loads and cuning forces also can be reduced by using the double-cutconstruction shown in Figure ·5. Pairs of teeth have the same size. but thefirst has extra-wide chip-breaker notches and removes metal over only a part ofits width. while the smooth second tooth completes the cut. Chip-breaker notchesare used on round broaches to break up the chips as shown in Figure ,-6.

Purpose Motion Construction Function

Single Push Solid RoughingCombination Pull Built-up Sizing

Stationary Burnishing

Classification of Broaches. Broaches commonly are classified as follows:

;.lOdthe work usually is a simple linear one. a rotational motion can be added10 permit the broaching of ~piral splines or gun-barrel rifling.

/;3

FIGURE 7 Progressive surfacebroach. (Courtesy Detroit Broach &Machine Cornpany.)

('[

I\. third construction for reducing tooth loads utilizes the principle illustratedin Figure -7. Employed primarily for broaching wide, flat surfaces, the firstfew teeth in progressive broaches completely machine the center, while suc­ceeding teeth are offset in two groups to complete the remainder of the surface.Rotor. double-cut, and progressive designs require the broach to be made longerthan if normal teeth were used, and they therefore can be used only on a machinehaving adequate stroke length. .

The faces of the teeth on surface broaches may be either normal to the direc­tion of motion or at an angle of from 5 to 20 degrees. The latter. shear-cut,broaches provide smoother cutting action with less tendency to vibrate. Othershapes that can be broached are shown in Figure 26-8 along with push- or pull­type broaches used for the job. The pitch of the teeth and the gullet betweenthem must be sufficient to provide ample room for chip clearance. All chipsproduced by a given tooth during its passage over the full length of the workpiecemust be contained in the space between successive teeth. At the same time, it

h

::

view])v'O'OIL _

Side

Top

Material Removal Processes

.:1,End

-I~,~!GURE 5 Overlapping succss-.ksivete~th permit targe RPT lwithout

_ tJncreasfngthe loa~ per tootn,~~~rJ

,~..--...~~:::~,~bJ~~~~~~~~~~J~~W~'UUUUlls~t: FIGURE ·6 Round, push-typef broach with chip-breaker grooves oni: alternate teeth except at the iinishingend. (Courtesy duMont Corp.)

Senes 01 4 1E-'~I"---'

q~'If:"'(."(j uoftion,)1 C;\lIIII'9 -,dqe

44

FIGURE ·9 Thegullet area pro-vides room for the chips. '

previous cu tExtra·wide spacing may be used when chip disposal is a problem

Chip adheri"9 to broach tooth will be displaced by the next chip formed

1----PiICh---1

'" .3sVLw

L r~,adius ofgullet

R 5!!O.25 P

FIGURE 8 Examplesof push­type and pull-type broaches. (Cour­tesy DuMont Coro.)

is desirable to have the pitch sufficiently small so that at least two or three teethare cutting at all times. See Figure ·9.

The hook determines the primary rake angle and is a function of the materialbeing cut. It is 15 to 20 degrees for steel and 6 to 8 degrees for cast iron. Back­off or end clearance angles are from I to 3 degrees to prevent rubbing.

IPuah-IYJH!Recl.Dlul.r Broach ttheu .n8lel for alun8 rec1angut.r hole. r"dar wave suld. n.n~_...!t,~_,..,8

7 • -mmtm[;Pu.h·lype "0" Hole Broach.Can .Iw be Imd.ln "Do"bl •.D~ .I,la.. :. .' .._:,,:'" ;:fi~~"'::".

rush·typr. Droach to cut two j(("pU)S tSO11~!Irenap.rt h, ene p.... Call .110he mad. fA 3 and 4 ka)'way 'Il~.6

____ :.,.ox..- ~ ._ •.

PtI_IHyp" cut-.nd·ntllsh Kt!YW8)' Broat:hwIll CUI an Intf'mal keyw.y, If.burr lb. keyw.y. and IInith th. bore ...all in nnr. patl.

g"rr"'r,,",*"-,'¥'i'a.a""d"'d"U~~~ ...U..U:nlnlnt ...

5:;::;._ .--< ...• ~- ":':: •._.-.'~--""""'__'-",~~""""""

4

3 ;':::1 .~, ... ',n.:!o: 1',"" !""~".•.; tl!Il.1l II ",jlh Ih"·.,,k<lt}'I'" pull rn'l. /

----- _.

"\JII"n"~ IIro8ch lor ,izln!! widlh 8ftd dt!plh 01 ,lui In on. operation .! ''''''''''''- .... r • -_"f"_

1.1

•Broaching, Sawing. Filing

Broach Materials and Construction. Because of the low cutting speedsemployed, most broaches are made of alloy or high-speed loot steel, even withsome mass-production work. TiN coatings of HSS broaches is becoming morec.ommon, greatly pro!onging t~e' life of .b~ache~. When they are used in con­unuous mass-production machines, particularly m surface broaching, tungstencarbide teeth may be used, permitting them to be used for long periods of timewithout resharpening.Most internal broaches are of solid construction. Quite often. however. they

are made of shells mounted on an arbor When the broach (or asection of it) is subject to rapid wear. a single shell can be replaced. This will

Broaching. Speeds. Broaching speeds are relatively low (25 to 20 sfpm),seldom exceeding 50 feet per minute. However, because a surface usually iscompleted in a single stroke, the productivity is high. A complete cycle usuallyrequires only from 5 to 30 seconds, with most of that time being taken up bythe return stroke, broach handling, and workpiece loading and unloading. Suchcutting conditions facilitate cooling and lubrication and result in very slow toolwear which reduces the necessity for frequent resharpening and prolongs thelife of the expensive broaching tool.For a given cutting speed and material. the force required to pull or push a

broach is a function of the tooth width, the step, and the number of teeth cutting.Consequently, it is necessary to design or specify a broach within the strokelength and power limitations of the machine on which it is to be used.

Most of the metal removal is done by the roughing lee/h. Sem~tjnishing teet;provide surface smoothness. whereas finishing teeth produce exact size. 00 .new broach all the finishing teeth usually are made the same size. As the firsfinishing teeth become worn. those behind continue the sizing function. On someround broaches. burnishing teeth are provided for finishing. These have 01

cutting edges but arc rounded disks that are from 0.00 I to 0.003 in. larger thatthe size of the hole. 'The resulting rubbing action smooths and sizes the holeThey are used primarily on cast iron and nonferrous metals.

The pull end of a broach provides a means of quickly attaching the broadto the pulling mechanism. The front pilot aligns the broach in the hole befor,it begins to cut, and the rear pilot keeps (he 1001 square with the finished holeas it leaves the workpiece. Shank length must be sufficient to permit the broadto pass through the workpiece and be attached to the puller before the firs',roughing tooth engages the work. If a broach is to be used on a vertical machinethat has a tool-handling mechanism, a tail is necessary.A broach should not be used to remove a greater depth of metal than that fOI

which it is designed-the sum of the steps of all the teeth. In designing work.pieces, a minimum of 0.020 in. should be provided on surfaces that are to bebroached, and about 'id in. is the practical maximum.

, -,.

',',

.'

'",~ r•~:.". •r1.~'~~&;.

<II; ~

rfI.~~~I9 I Material Removal Processes

.-Ii~IIiIf

- .,' ~- _I ~i

~~_ r:.~~fi-f~~"- i:;',.

~~

Vertical Pull-Down Machines. The major components of vertical pull­down machines are a worktable. usually having a spherical-seated workholdera broach elevator above the table. and a pulling mechanism below the table. A~shown in Figure 2. when the elevator raises the broach above the table thework can be placed into position. The elevator then lowers the pilot end of thebroach through the hole in the workpiece. where it is engaged by the puller.The elevator then releases the upper end of {he broach, and it is pulled throughthe workpiece. The workpieces are removed from the table, and the broach israised upward to be engaged by the elevator mechanism. In some cases whereinmachines have two rams, they are arranged so that one broach is being pulleddown while the work is being unloaded and the broach raised at the other station.

Broaching Presses. As shown in Figure. 12, broaching presses essentially are arbor presses with a guided ram. They are used with push broacheshave a capacity of from 5 to 50 Ions. and are used only for internal broachingThe forward guide of the broach is inserted through the hole in the workpiec.as it rests on (he press table. often in a fixture. As the ram descends. it engage.the upper end of the broach and pushes it through the work.

Broaching presses arc relatively slow. in comparison with other broachinjmachines. but they are inexpensive, flexible. and can be used for other types o·operations, such as bending and staking.

TIle choice between vertical and horizontal machines is determined primarilby the length of the stroke required and the available floor space. Vertic.machines seldom have strokes greater than 60 inches because of height limitetions. Horizontal machines can have almost any length of stroke, but they requir.greater floor space.

Special typesPullSurfaceContinuous

Broaching presses (push broaching)Pull down (Figure 26-2)Pull upSurface

RotaryHorizontalVertical

Because all (he factors that determine the shape of the machined surface (11

that determine all cutting conditions except speed are built into the broachu1001. broaching machines are relatively simple. Their primary functions arcimpart plain reciprocating motion 10 the broach and to provide a means f.automatically handling the broach.

Most broaching machines are driven hydraulically, although mechanical dri.is used in a few special types. The major classification relates to whether tlmot inn or the broach is vertical or horizontal, as follows:

/'

Broaching Machines

Material Removal Processes

,.,,,

I'

/'

F!GURE 12 Arborpressusedtobroach keyway in a gear.

Broaching. Sawing. Filing

".~

ji'

Ji

I:'( ~ 1- .J ~

t',f

c-' i!T_ '1

'.I-,fI~~J

Ifil ~:i( ~rIi, rujr. I

~_ ~ In Figure -2. the part is being broached in t\VO passes, first on the [eft, then

en j on the right.e: e1L r VerticalPull-UpMachines. In vertical pull-up machines. the pulling ram!c. I is above the worktable and the broach-handling mechanism below it. The work!c r is placed in position, above the pilot. while the broach is lowered. The handling

t mechanism then raises the broach until it engages the puller head. As the broachnl-~ is pulled upward. the work comes to rest against the underside of the table.0, i where it is held until the broach has been pulled through. The work then falls

~ free. often sliding down a chute into a tote bin.-~ Pull-up machines may have up to eight rams. Because the workpieces need,. I only be .placep in the ~achines, and_the broach ha.ndling and work removal ~e

r I auto~atlc: t~ey are highly productive. For certain types of work, automatic< t feeding can be provided,~ f 'e I Vertical Surtace-BroachinqMachines. On vertical surface-broaching

~ machines the broaches usually are mounted on guided slides to provide supportt against lateral thrust. Because there is no needfor handling the broach, they are

.~~.~.;~ ),I

'j, .

(b)(a)

Rotary BroachingMachines. In rotary broaching machines. occasionsused in mass production, the broaches are stationary. and the work is pas:

Continuous Surface-Broaching Machines. In continuous. surfabroaching machines, the broaches usually are stationary. and the work is putpast the cutters by means of an endless conveyor. Fixtures are usually attaclto the conveyor chain so that the workpieces can be placed in them at one {of [he machine and removed at the other, sometimes automatically. Such rchines are being used increasingly in mass production (see Figure 14).

Horizontal Broaching Machines. The primary reason for employin;horizontal configuration lor pull- and surface-broaching machines is to rmpossible longer strokes and the use of longer broaches than can be convenieraccommodated in vertical machines. Horizontal pull-broaching machinesvertical machines turned on their side. Sec Figure J 3. When internal surfaare to be broached, such as holes. the broach must have a diameter-to-lenratio large enough to make it self-supporting without appreciable deflectsConsequently. horizontal machines are seldom used for small holes. ln surf;broaching. the broach is always supported in guides and therefore no Sllimitation is encountered. See Figure 14. Broaching that requires rotationthe broach. as in rifling and spiral splines. usually is done on horizoimachines. /

simpler but much heavier than pull- or push-broaching machines. Many h;two Of more slides so rhat work can be loaded at one while another par.machined at the other. The operating cycle is very short as there is no handlof the broach. Slide or rotary-indexing fixtures are usually used to hold'work. This reduces {he work-handling lime and minimizes the total cycle tit

FIGURE . 13 Broaching the teethin a gear segment by horizontal sur­face broachingin onepass. (Cour­tesy Apex Broach and MachineCompanyJ

. Material Removal Processes

~.~.~:~.

f~Ii:.~. I

;

/

IA

Astage

, .

Brooch

6Iindfng wheel

U)

staDeJ

Section A-A2nd

~ Sp!fnt'J sectionIi)

1st

tnrotut«~_"""'---'''''__'''''r--~ ~--.Jt-.__,_ "~

.-mIf)

(e)

~H-++-lJ.-,-lI -+-

~-L_J~~~C~~

-8-~~~[cJ

fiBEEEffi@-fID·_'(d)

.--@

Fi!

'aceIlL,;1 • :en•.

ont, ;)'-_{

, .... :,

SLJlI If iJnmlll#r ~ ~ ~ wWtlJ ~'!211 tolTr!l: .r-.:.. .'Fig. 363. Kryway oraache!

.:. "

i,

Fig. J52. Combination round and spline broach

;~.:~

'0

rw(1I JhOf)( tor Q splil)(htlgltf /f({ tJmm

(Q)

Fig. 351. Teeth 01 a round bumii1lng broach:(0) broach wlln a.sumhltd bllrnly,{ng ~l({: (b) WOpt 01 (ht burn/shu,

51

Mod~s 01 cutting in broaching:) lull-form; (b} genuatlon; (c) s/Dfftrtd. (d) al tcrna tr and mufJiplt-~Jdu!

tdJ(C)

(ptugrroivt rrodt of cutti.JJq jJ!. Group-clll broaches

(b)(a)

---

(a)

S 7

f'-It~[~.til;ll4-L__J

1

/

The objective of the optimum design of broaches is toattain the maxim urn production rate together with theminimum tooling cost per piece and at the same time toobtain the quality of the machined surfaces. Theconstraints are the maxim urn permisslbto broaching ~9r~e;dictateo ny tne capacity or the broachinq machine, thestrength of the broach.rnlntmum tooth space required toreceive the removed chips, maximum allowable toothpitch which permits at least two teeth in contact to avoidbreakage of broachrnlnlrnum feed per tooth required toavoid rubbing without cuttlnq, maximum permissiblebroach length according to the stroke of the macnme andfinally the maximum permissible power as limited by thepower of the installed motor.

~. --1~," 1

i:~<;{ The OptimufTl Desig~ of Broaches:f1

Broaches are used for machining almost ail typesof internal surfaces (e.g. key ways, spiined,serratedholes and finishing of holes.etc) as welt as externalsurfaces, 'with a high degree of accuracy and surfacequality, and with relatively higher production ratesthan other c6nventional machining methods. lnspiteof thewide variety of broaches required in practice,the design procedure (forces, stress, powercalculations, assignment of tool geometry ..etc) ispractically the same, which provides a typical field fOTthe application of "CAD".

Broaching, tools9J)e4~41/ recdoa~

, ' l

" ,0,030,050,10,1

1234-

Steel, 'C.l.BrassAluminium

"

Szr(MM! tooth)

Code(M)

Material

Table 1 •. Recommended'Values' for the feed, , per .toot~ (S~)

S 'f!:: 0.02 mm, S f= 0 ,zs ' ,,' z '",The feed per-:-tooth for roughing' tee,th ,('8 ) is, tp 'be :deter.riIinedaec cr'da ng to the workpiece material (Co~~.M; which ;,takes dlifere,val.ues for dii'f~rent workpiece,:materials)." table ,1J' ''''''', " ".

'. . .".:....... "

I~'

I,

Type Code..A. code (B) is used to diff erentiate between the di~f ar en

types of broaches figure (2) as follows:B = 0 'for keJoay broachesB = 1 for 'splined broachesB = 2 for eire ular broaches

,f' 'Broach Feed Der Tooth,

The feed' per' bootrh figure' (2) is selected from establish(practical values according to the art of the broach teeth whethcthey' are roughing, semi finishing .or 'finis~ng teeth. The 'vaLue

, of the feed per tooth recommended for semi finishing. (S 'f) .andfor finishiI?g (Szt') -ar e /6/: zs .

! '

i;r Broach

- I,

I I~ order to attain maximum production rate the f'eed peritooth in tile rO,pghing part of the broach saould be se Lecced~as'large as possible, on condi tion that the maxi.mumat r-eaa at

_ ~tl~8 tooth, root and ~t the broach ~ea.1c95t sec~ion as well as~tb€ .broacning c ap ac.i.ty of 'the av a.i.Lab Le zaactune are not eXCe~-

,ded. This resul ts in the minimumnumber of roughing teethrequired to reillo-ye the ,given machi.t;rlng ~lowance.' On,the o t hehand the sma.LLes t P,~_~s)hl_e_tQ9_~l;l__p'~~,_,~QQ_~4,,_q_~2:_~o,s~p' ,~_o that

j the_"min].-m'UUL_ur_o,~gQ.,__l~Dg~!l_'C@_~~ __,.2bt,~~_~d, which, he Ips inre{lticing the tool matara aL, tool manufacturing and tool regrin·

, dillg costs. The minimum br-oachi.ng coat per piece can be atrt ai.;W-edby the selection of the ecoriomic cutting speed correspondin{tl to the optimum tool ,life • The, proper aeLectri.on of the tool

- ~ge.umetry in the semi finishing ,and in -:;he finishing sections 01~t4e broach results in attaining the required a~curacy and~surface quali ty • /1~

z ~ 11'lT (Z)eml" .v c,j..V

In order to avoid the 'br-eakage of the broach the m:rJULl numbe r of teeth in contact -(Zcm~h)should not be less tlIn case Zcrzll,,\_.0 it should be taken 29 ~.Dd the pitch has t~modifiec!ac'cordingly. ~e maxi.mum nunoor of teeth in cornis G~ven by: --Zc= Zcmil'l+ 1. Tr...e too tih ' dimensi ens f ie;uJ:'e (2) are de due tfro~ the pitch as 'follow3:" -

H = 0.4 Pr9' :r, ::: 0.2 Pr1 g = O~35 ~r

The too th pitch for. semi£ini{Jhing and finishing te-eth areequal, to Pr,' ,so that the aema ,finishing and the finishingwill have the same dimensions 'as ,the roughing teeth. _ ThegeoQetry is determined according'to the workpiece material

pisplay' of the,Tooth Shape

The tooth can be displayed only if the coordinateBits different points are given 0' " These'-coordinates are ol~tin the longitudenal section-figure' (3)as follows: The or!of the coordinates is_tak~D at the ,tooth nose (0,0). Th~coordinates of the centre of !the .chip space fillet are:

'Y_- =: p .'_ ( _F..:,.._ .... (H- r) tan. )-~ r cos r,Y1 ~ ( H - r )

K' ;: (50 -~ I 5"

," -

The ~ounded number of teeth is obtained Dy tr~catipg the~rc1-ctionalnert of rZ ') or-- - \ cav '

of teeth ill contact wi th thegiven by

(t~,-: ,

and JJ is the workpi.ec e lengt_4~-'. . .k is the chip sp ac e factor~__e _3_=-= _6

The average numb ermachined s ur f ac e (Z~ }~r isva'.

Ilr:cach Toott Pi tc h-

L3pr

'. .

r (j') = I (j) ... j Pz:Y (j) '= Y (j) + j Szr ...j = 0, 1, 2, ..... ~ Zr .'f~r·.roughing teeth

In:case of semi finishing and finishine teeth the correspond­ing values of S;..and Z are considered.' In this' way the broachteeth oan b~ displayed on the VDU·an~ I or .plotted on the graphplott·er. .. I . .

- ~h~' ~ncJr1riln~)J.l-ow·~ce in Broaching'·'.: :7 .: :--';-~"-.=:: '. '. -:-: .- ~

\ "This- 'includes the ·:allowance. for roughing t aemi,'finishingand ,finishing. In case of hole 'mach~ng, it is given as R,' .f~c~i9n of the bp;te diameter. Cd1) and 'lengt~ (L) as follows/6/:

, 1.1 :: 0.005 01 + 0.1 (L

Th~ ~uccessive teeth have their origins shifted by the ,pitchand its cu1ti~les for the X - coordinates, and by the f~ed pertooth·and its ~ultiples. for the Y - c~o~dinates so that th~coordinr;tes of the corresponding points .on the different teeth-till bet

., ( ~ _ ;_)2qr :: V ..6.1 -c: -+

,

arc'sin ( ~_-_Y2 - r ). y/ 1 (. r )___ _, + arc, 1. (f ?

r

e-e r sin e---...+ (cos e?

3e :::

on the secODd~~ flank

t ~ (j' 2~ = gY2 = (g-f) tan ex :J

coordinates of the blending point

g tan eX,.

g

f'"-I

~~)!.I(F,

- ~'&:

tne end point on tbe mai.n flank has the coordinates: '~-_ ~~!:~ V _~ ~2 -~~or semi finishing and finishing· teeth a facet (f) is provided~o:that the end point of the facet has the coordinates (fto)~toordinates of the end point on the flank are:- ~~;

¥

55.'

,',

'"•

Since the number of ,teeth shouJ.d be an int~ger, It will brounded to the next higher figure or: "'-'_'' ,

Zr:: 'IliT (Zr' + l)The acttiai'value of 'the feed'per'tootll will then be:

S _ AIzr - -zr --!-

-'r = '~ - ( J.si + ":r)A. = total allowan'ce' 1"Yo,m one side

The number of ro ugbing' teeth Z is,rZ _ .Arr - B,zr

The roughing allowance 13 tberefore

As!= Sza~ a Zaf'

A_r e Szf • z..r

Zf = 5. - 8Z5f= 4 - 6

The al.Lowances for semi finishing and finishing teeth ar­given as follows;

The numbers of semi finishing and finishing teetbtaken as follows as recommended b7 current practice, /6//7/, /8/:

However the number of broach t~~th are det~rmined on thbasis of the feed per tooth on- one sid~ t ,e. using h~the value of A~. The*total allowance from one side is:~ .

!: = Yz ~ = 0.0025 ~ + 0.05 (LFor wor-koi.ece shapes .other than the circular type, tb.~allowa.nc~ is de ter!Iti.ned as the difference between 'che utliEit of tile f.lnal dimension (d,) max and 1(he Lower lim:of the ini tial dimension (d1) tUn (for internal bro acair

.' ~ :: (d2) max .; (d1) min ..... (for k~yway 'bn~ =}ll ~9-2) max - (dl) mJ..n)_.(for splined br.os

liumber o~ the Broach Teeth

·.!

-t,

---,:.t'o·

The last broach only will have s'emi -.finishing and finishl,ng'tee'tn'in a1di tLon to the roughing teeth, while the preceedi.ngb'r,oacll~8will have r-oughLng teeth only.

.A:rThe machining allowance for ea-ch broach will be! ss: -= -0 ·

+ 1,)-' -

~ ~Pl -: length of front pilot - length of the machined partre~ L 2 =' length of rear pilot-- .p, -,-

~ The maxi.mum broach length eLm) .1's limited -by -the S"troke length__ I' .. o~..~h~,~v~labe broaching machine as. well as by the limitations, .' d~,ctateCl b:r,tbe beat-treatment techn~'iue. In case ~) ~ ,. several broaches should be used. The minimum number (n)' of

br-oaches required to remove the given machining allowance isdetermaned as follows:

~n -:: -INT ( t;-

L.o .:::10 + Lpl + Pr (Zr + Ze) + P sf· Zsf+ Pr- Zf + LJ,Z/'

10 .:::front end lell¬ threq~ired for the clamping jaw and lengthof the machine b ushj.ng ,

i~;\-i~ ,~.

01 1-y t

The total broach length is determined from the lengtboof its individl'al sections as follows!,

_ t

1)1NT (Z :::::e

In order to avoid overloading of the first rough;ngtooth in case of IDacilinjDg I1ats fro~ round section (is e.g.ke~ay$, splincd holes and polJson~ shape5), auxili~rteetb are used as prcwachining te~t4 abead of tbe firstrougbirig t ooth to r-emove the adciiticnal allowance (e) figtrre(4). ~rrenunber of prem~chiDin£ teeth (Z ) is deduced f~mthe premechining allowanc~ (e) given bYl ~: ?~~_x __ ~

e ;::f ~ V d? - p2

S':(1

The maximum stress in' the broach body 18 calculatedftt the rointJnum cross section which is either g.t; the neck 0~t tbe root of the first tooth. The StreGe_is given bytI.

Stresses in the Broach Cross Secti on._---

-fh,~modified values of' CPr) and (8 .) are introduced 'and 'Jl;alculati()Ds are repeated untill tfiii conditions Fb'~ <F-i,·iifulfilled.

------.,...Pr ::Pr··

The broaching forC~ sr..vuld not exceed the maximum ¥ermiSSforce (Fp) 'offered by the machine. Tnc as e F},> F'p , he fee

Per tooth (S ) sucul.d be modified: .zr p:p 1

S~'r:= Szr .( 11b -) f-Iiif

The ~alcula.tioD~ are repeated with this ~odified value of(SzrJ, on condition that it wi11 Dot be less than a givenmiDl.mwnvalue (,szr) min, to avod.d rubbing without cut·tfIlg.In case Sz,r .< (Szr) min, the minimUlIl permissible val ue '11taken and the :pitch is increased 10 the .ratio:

( Szr}min

t-

\

~ :: Sz:rThe total force .ac t Lng on tbe'broach iF:

Toe 'B~c~in!!; Force

The broaching; .force per tooth is given by /7/:.., 5 K b r I-m.f

Fhz = ..1.. 81.1 1 -1The specif.i..c cutting ~orce (Rsl.l) 8LC~ the eX'".t!(}~enl(r:rr).are determined accord~Ilg to tl~'3 wor)r,pJ.'''::CE: IDaterl~.t anc, t!t ool geoI!letry. According to i.h e tJpe of the Via!. kpi ec e t ;width of cut (bl) t a dete;:-rnj_ncd. 'I'ue uncut chip t.h i c kne s(h1'; i3:

. j

oS -:z.~

& The mOB~ econo~ic cutting s~e~d '(v)is given as a>; function of the optimum tool' life \To.pt) and the' feed per

lE tooth (Szr) as .follows i1i

i~ Determination

Sz:.c-If

......

1 other Wi3eeire ular broaches j

,'\'9 ~...

Tbe co r.e ~rca CAe) is to be deducacl from the cODstructionalIdruwipg 01. the broach"

_1~,.§~_8in the B!-::<,,,chTee~

I Bending stresses Can be c aLcu.Lated at the tooth root_ for keywcy and spl i.ned broaches cn.Ly," Tr.~ maximumbendingIst~'e's5at the tooth root is given by~:

;~I: E. )'J,~--!

i~- M The .maxi eua ahear- Bt~G8 at the tooth CNSS section is:!1

_J~

11 j ;:;~ 'f... is a stress distr1bution factor dependirus on the ratio

i _r big. In cas e ~"1Y of the stresses (619 6.1 r y,), exceeds thej pe;missihle va.Lues 1 the feed pBX' tooth should be reduced._-~

•j

L;~~~_ ..~~..~~~:~

Kr = ratio of cutting sPeed to return spee.-::_0..4

4

The broaching time consists of the actual machiniDtt{!j(;; and'the time for the repid:l:eturn, i-n addition ·ti),·~henon product i,v:« time (tn) required for tool and workpiecehan?ling. It Lsvg i.v.en a ava function 'of the broach length(Lb) t the workpj.e ce length (l,)a.nd the cutting speed (V) :

~ + L' .tb = < V --) ( 1 + Kr) + tn

(P tIl)v·~ v --p~-

~vtorThe power consumed int~rmiDals is givep by:

'F VP = b'.·60.000 ~

~h~ Gverall efficiency ~ = 0.6. The .power (p) requiredbr-oscuing is compared with that of the installed motor (:EII: case (?) exceeds (Pm)-a modification of the cutting s~i:> requi.r-eo, 8S follows:

the broaching process at thE

Pove~ ~onsumption in Broacping

is t ae tccost and

~lCl is t he machine and labour hour rate while C2inG C0St rate (tool capital·cost, tool cha~si~~re5rindillb cost) per regrind •. Cz /C \ :~100

)I-tIl. (Top\; =:

a factor depending on,wor~?iece and broach Dateria:~~o~~ geometry, cutting f'Luid ••• et c . ,~, 15 hrf" ~-I:;s~.stw dud ~ are exuonecta (m = q = d.6, /6/)

Tbe c:;~i:.:um tool life (-ropt) is that which lead_s to minirmach1··".l.·!J.6- cost. Similar to other m.achintng processes th~....0-.; ... In'0p~i~u~um tool life is given by I ~/:

i. ~:

\I'

.~--

...;, .~~.7···~:~.!:.

~: ........ ".:;J;

._ (; 0_

"

r, ~f<.

_,4

f,~~.I

- ~.Ir­':j'

0- ~ .C' '- ~.!

. -Spl~~ hole ~~ah

.' I

00+-

.m

. :1.',.'

:1!j

I

-:61-

" "

'i."!1::_~j ~:"'i:l] -:i

FiCUrl ,. C..rii~8tca .f the •• inpeinta en', the b~eh teeth

'filU.hins t •• th

" '

, 0<1{:(,0) , X

i -

..

",~, " J

..;

; -~62'-

:',"

',I'..''.

!l

{~.".t1-r

r

.Logic" rlo1f' d1agrBlll tor-····the c?mnut:A~ • l,.l ~.a •

.: b3 _ Pigurt 5.

.::1·), , : ~z;-~~~~'~r~Z8:r;Zt:,~,n,v,P,tb .

,.t;.

._ '.' .~..-y

I -r", III

t:-.. '

.' (-

: '!.

D :I AIN7(?- .. 1).......

A=O.C025d,.1...

r':

'. A!-s -~zrT ~ , ..-..'r·

• ~ C?5dl~O.5eZ =r -s--e .......

A: l( d2 - d,) .#= A - A~r

:\' =: d.,G

\ -:J It.,r .

- T:he ~uttin.g.speed -I n broaching iz given by

V15 )'\jh ' ,=

0.62 0.62T Sz

Tool material nss ) ti~

,Workpiece C 4S C 35 st 42 St 70 C. r ALU

mate rial ST60 St50

l<ni 1 1,25 1,-s 0.8 0.6 2.5-

lif~ relation ship.

koi t '1 t' r- t . (tJ,- ) of t he .too IIv.or. pi ece. rna (rCo. cor rec 10n rac or n -m_

"

"

TABLE -1

Stede 10 - 15 15 - 18 1.5 - J 0.5 - 1C.;I 4 - 6 10 ' 2 - 5 I 0.5.- 1I J_. 2Brass 5 8 - J 0.5 - 1

Bronze 8 8 lor 0 - 0..5I .-:;l

AL 18 - 22 25 14 - 7 -2 - 4I .-- ..._....

material

Tool ang.les ::orb.roach teeth

0.2 - 001 0.05 ~ 0.2

~~------------~----------------_j

l Bronze&Bras. 0.05 -_ 0.12 0.2

0.06 - 0.150.04 - 0.1

0.04 - 0.06 0.2

!-----------..-~--------.-~,----,---,--_!._-+-_. . __;.__S-'P_l_i_U_C_Cl_· '_,_ key:.:_y I

i

Type ot broach-_

II

!

IIRoundI

I0.02 - 0.05 I

!0.0) - 0.06 iI I

I 0';05 0.1 I~ I

I 0.02 ~ 0.05I ..

r:-:r xl' i-e c e, fil~terial

r St~ol

.,., '~

.f.~-----------~---------------r_----------~------_+-------------.-Ir~i.i_ r;i

Ii

\.

-------~------------------------------------.

Table 1 I rcco~nended values for the fEed Der tooth S~r

De8i~ data for BToeche~.i

- ....r--'1tr ...

I._ ....d1 +0-........--......." ASl-.....

-~ 1----------------r-------------~o-~--------------~------------------------~o--·f Workpiece rake angle ;r Clearan, ce angle 0(

'roughing semi~finishing roughing' semd,finishingf:Lniahing & f iniahing

65

Fundamentals ofMilling Processes

Introduction

Milling operations can be classified into two broad categories caJled peripheralmilling and face milling. Each has many variations.

In peripheral milling the surface is generated by teeth located on the peripheryof the cutter body. See Figure ·1. The surface is parallel with the axis ofrotation of the cutter. Both flat and formed surfaces can be produced by thismethod, the cross section of the resulting surface corresponding to the axialcontour of the cutter. This process is often called slab milling and is usuallyperformed on horizontal spindle machines. ln slab milling. the tool rotates(mills) at some rpm (N) while the work feeds past the tool at a rate fm.

Milling is a basic machining process by which a surface is generated progres­sively by the removal of chips from a workpiece fed into a rotating cutter in adirection perpendicular to the axis of the cutter. Sometimes the workpiece re­mains stationary, and the cutter is fed to the work. In nearly all cases, a multiple­tooth cutter is used so that the material removal rate is high. Often the desiredsurface is obtained in a single pass of the cutter or work and. because very goodsurface finish can be obtained. milling is particularly well suited to and widely"used for mass-production work. Several types of milling machines are used.ranging from relatively simple and versatile machines that are used for general­purpose machining in job shops and tool-and-die work to highly specializedmachines for mass production. Unquestionably. more Hat surfaces are producedby milling than by any other machining process.The cutting tool used in milling is known as a milling cutter. Equally spaced

peripheral teeth will intermittently engage and machine the workpiece. This iscalled interrupted cutting.

Milling

r:

" -..'

i,.,!j

fI

Values for 1, are given in Table I along with recommended cutting speeds.In face milling and end milling, the generated surface is at right angles to the

cutter axis. Most of the cutting is done by the peripheral portions of the teeth,with the face portions providing some finishing action. Face milling is.done onboth horizontal-spindle and vertical-spindle machines.

The too) rotates (face mills) at some rpm (N) while the work feeds past-the tool.See figure' 2. The surface cutting -speed is related to the cutting diameter Daccording to equation 1 in surface fee! per minute. The depth Q,f but is t in

-5)The MRR = Vol/CT ::: LWt/Cf = wtfm in.3/min., ignoring LA-

where n is the number of teeth in the cutter (teeth/rev.). Given a selected cuttingspeed, V, and feed, t, fer a given work material and tool material combination,the spindle rpm is computed from equation 25-1. The cutting velocity is thatwhich occurs at the cutting edges of the milling cutter.

The cutting lime = CT := (L + LA)/ 1m in minutes, where -3)

the length of approach = L4 = iD2 _ (e. _ t) 2 = Vr (D - t -4), V 4 2

2)i; = f,Nn

in surface feet per minute where 0 is in inches. The depth of cut is t in inches.The width of cut is the width of the culler or the work in inches and is giventhe symbol W. The length of the cut, L. is the length of the work plus someallowance, LA' for approach and overtravel.

The feed of the table. t.: in inches per minute is related to the amount ofmetal each tool removes during a revolution (this is called the feed per tooth).I" according to

-I)V = nDN/ 12.

The surface cutting speed is established by the cutter of diameter (0) accordingto

Slab miliing - multipie tooth~ '_~_or_k~_~:_ec_e ~

"l'.

. f Basics of the miningr:orn,·'_',,:-'-Peripheral or slab milling.

see Fi~ure 25-8.

Materia! Fiemoval Processes

6=!-

FIGURE ·4 Climb cut (or dowrmilling versus conventional cut (or tmilling for slab or end milling.

·3 Face milling MR

/

FIGUREup milling.

F~orendmillill9

Peripherial orslab milling

Cutting forcesoppose feed

Conventional cut{up milling)

8Iade~i"scutting, takif19thin chip hereand Ibruptlyleaves cut here

Thin chip atentry with.brupt exit

.......-?§i'=r---,~DePth-Y0fCU1

L- ~~-J

(Up milling) conventional cut

Cutting forC2Spull workpiecetoward cutter

FHd ----- __

Blade takesthick chips hereMId tases outof cut here

(Down milling) climb cut

Climb cut(down milling)

MAR =Wt fm

-:;. -

Rotation O' to 360· of cutter,

...-----.----180" :-270'180"

conditions create a built-up edge lin the cuuing edge. the BUE will not affethe surface in climb milling.

In down milling, maximum chip thickness occurs close to the point at whit(he tooth contacts the work. Because the relative motion lends to pull the worpiece into the cutter. any possibility of looseness in the table feed screw rnube eliminated if down milling is to be used. It should never be attempted (machines that are not designed for this type of milling. Virtually all mode!milling machines are capable of doing down milling. Because the material yiehin approximately a tangential direction at the end of {he tooth engagement. the:is less tendency for the machined surface to show toothrnurks (than when l

milling is used) and the cutting process is smoother with less chatter. Aneth.advantage of down milling is that the cutting force tends 10 hold the work againthe machine table, permitting lower clamping forces. However, the fact that thcutter teeth strike against the surface of the work at the beginning of each chican be a disadvantage if the workpiece has a hard surface. as castings sometimedo. This may cause the teeth to dull rapidly. Metals that readily work-hordeshould be climb milled.

Milling is an interrupted cutting process wherein entering and leaving the cisubjects the tool to impact loading. cyclic heating. and cyclic cutting forces. /\shown in Figure ·5. the culti~orce. Fr. builds rapidly as the tool enters thowork at @ and progresses to @. peaks as the blade crosses the direction 0

feed at ©. decreases [0 @. and then drops to zero abruptly upon exit. Th­diagram docs not indicate the impulse loads caused by impacts. The interruptedcut phenomenon explains in large part why milling cutter teeth arc designed Ithave small positive or negative rakes. particularly when the tool material icarbide or ceramic. These brittle materials tend to be very strong in compressionand negative rake results in the cutting edges' being placed in compression b~the cutting forces rather than tension. Cutlers made from HSS are made wit Ipositive rakes, in the main. but must be run at lower speeds. Positive rake tend:to lift the workpiece while negative rakes compress the workpiece and allovheavier cuts to be made. Table 25.2 summarizes some additional milling prob­lems.

FUR E 5 . Conventional face~illing(left) with cutting force oia-I m for Fe (rig_!:,D,'showing the inter­I led nature of the process. (From~etalCutting Principles, 2nd ed.. In­~ersOIlCutting Tool Company.)

nJ; .uP[tlr-

r

T

.(

Iw,,';d;··~~1"

Milling CuttersMilling cutters can be classified according to [he way the cutter is mounted inthe machine [001. Arbor cutters have a center hole so they can be mounted onan arbor. Shank cutters have either a tapered or straight integral shank. Thosewith tapered shanks can be mounted directly in the milling machine spindle,whereas straight-shank cutters are held in a chuck. Facing cutters usually arebolted to the end of a stub arbor. Common types of milling cutters, classifiedin this manner. are as follows:

Add sui fur-based oilRed{ce cutting speedFlood coolant

Decrease feed/toothUse CUller with more teethReduce table feed

Enlarge feedSharpen cutter

Check to see that workpiece is not deflecis securely clamped

Decrease feed/tooth or number of teeth iAdd blending oil to coolantCheck to see if all teeth are set at same I

Check tool angles

Decrease number of teeth in contact witlAdjust cutting fluid to wash chips out of

Decrease feed/tooth or number of teethwith work

Sharpen or replaceFlood coolantUse helical cutter

Use larger arbors

i. Radial relief too great2. Rake angle too large3. Improper speed

l. Cut is too light

2. Insufficient radial relief3. Land too wide

I. Not enough lubricant2. Speed too high

1. Feed too high

J. Dull cutter4. Poor lubrication5 .. Straight- tooth cutter6. Radial relief too great7. Rubbing. insufficient clearance

I. High cutting load causing deflection2. Chip packing3. Chips not cleaned away before mounting new

piece of work

I. CUlling load too great2. Insufficient coolantI. Feed too high2. Tool dull3. Speed too low4. Not enough cutter teeth

I. Lack of rigidity in machine, fixtures. arbor, orworkpiece

2. CUlling load too great

Teeth breaking

Cutter bums

Work burnishing

Cutter digs in (hogsinto work)

Poor surface finish

Cutter rapidly dulls

Loss of accuracy(cannot hold size)

Charter (vibration)

Cures

M

TABLE

Probable Cause

2 Probable Causes of Milling Problems

Problem

·.it

FormInsert toothSlitting saw

~'O' ".'~

Staggeredtooth

Helical plainSide • \Drivekey

Arbor bearing surface foroutboard support

Shank with..,.,......--#50 taper

Slot. for spindledrive keys

Figures ,6 and 7 show several types of arbor-type and shank-type millingcutters. respectively.

Another method of classification applies only to face and end-mill cutters andrelates to the direction of rotation. A right-hand cutter must rotate counterclock­wise when viewed from the front end of the machine spindle. Similarly. a left­hand cutter must rotate clockwise. All other CUtlersean be reversed on the arbor

Form Woodruff key scatFly Fly

End millsSolidsInserted-toothShellHollow

T-siol

PlainSideStaggered-toothSiitting sawsAngkInserted-tooth

Shank CuttersArbor Cutters

I1

}.

f

FIGURE ::j. -6 Arbor (2 views) andarbor-typemilling cutters.

Material Removal Processes

FIGURE -9 .of solid (HSS) Geometrical tealmilling. arbor cutlers for

Solid HelicalPlain Milling Cutter

Solid FormRelieved Milling Cutter

1-Facewidth ---=-1Helical teeth

Offset __ -\-.....).._'l--J~

Fillet

Helical rake angle{Ln. helix shown I

\Radial rake angle(positive shown) Axial

feliefangle

Radialreliefangle

Radialrake angle(positiveshown)

Chip space

Clear<lr>cesurf ace

t,:.,

Axial (~Iioef angle.:

~--Pef' '"// Ip"er~f c::qing edge

/Radial lehef angle

_l _-r------...:--=-==-~I

C!ear,mcp.~Ull3ce

:;'. ,

1(. The side cutting edges are seconda-ry in:cutting grooves and become principal when milling is performedwiththe cutter end face (as shown in Fig. 126c). Triple-end cuttersare, used for cutting deep grooves .. A ngular cutters (Fig. 126d) are employed in milling angular groovesand .incl ined surfaces. They find the most wide application in toolproduction for m ill ing chip flutes on various cutting tools. Small-sizeangular cutters are end mills with cylindrical and taper shanks.

Types of milling Gutters and schemes of milling

(k)flute

- Insertedtooth.

Cutterbody

ToothCutter hole

End tooth

r,~'fJ,:"

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~--._--_._ --_., -----~---------------..

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The manufacturing process used for the production. of carbide­tipped, bent-shank lead-angle turning tools consists of the followingsequence of operations:

~1)cutting off the stock into lengths for one shank ·(Fig. i33a);(2) 'bending over the tool point (Fig. 133b);,(3} milling the base of the tool (Fig. 133c);(4) milling ·the locating side surface of the 'shank;(5) cleaning up the end face, chamfering and burring;(6). milling ·the main flank on the shank (Fig. 133d);(7) milling the auxiliary flank on' the shank;(8) 'milling-the recess for the tip' (Fig. 1B3e);

. ·(9J burring the' recess.for the tip; =, /

.. (f'O) brazing :.·on.the' cemented-carbide tip;'{iil cleaning .the tool in a sandblasting machine;.{12)..grinding the main flank on the shank; ..(13) grinding the auxiliary flanks on the shank;. (f.4) sharpening-by 'grinding the main relief angles on the carbide. : ··.·::·tip:{Fig::::133f); ~"::- :. '.. {'i5) .Sharpening by grinding the auxiliary relief surfaces' on _t~e

, :.' ii' carbid~·.Jip.3,CFig.'-.~~3g); .. ' .. .. .-{f6) .·sharp:eiiilig·~bi.~griil.ding··.theland. on' the tool face;

: ·':'{17) ·griiid.i~g:~Jhe-.~~n~:ise~r!~di~s;-"".:'.> .... : .' '.' .. {1&) -Iappirig ~h~:::~ace,':~flanks.and nose radius (Fig. 133h);'':~.~<19) .inspecti 6n"~~.'·apd ··~:'·~arkin~. ...... > : ....:-:~~../(::::_.:.:.:-,' '.:.:.: .

-1, Single-Point Tool Production

STANDARD CUTTING TOOL MANUFACTURINGPROCESSES

CH-\.PTER

Manufacturingof

Cutting Tools

\

(I).

Fig. 133. Principal operations in machining lead-angle turning tools'. '. . :...... ' .. '''';' ,. . ....

! --

View facingarrow A

~(9)

, ,2.';:"T~per:-Sh~nk·:Twist Drill' Production /,T~p~r~~h~~~.k:.t~~ist::drills9f'high-speed steel are made by a manu- '

facturl~~iLrp..~.J~IlSlS~l~~ _or tne I~I~2wlng'sequence or opera uons:. (1}"~~IidJ2Lc.ut,~ing on .t~e )llanks ror -LIle,bony ana .,lnrriK; '.

(3)"and (4) cleaning up the end faces of the body and shank blanks;",:,_ ..... . . '. .' ,... ". -' .

machining of several blanks ,are employed to increase the outputin milling the tool flanks and the recess for the tip: The blanks areset in the fixture so that, the surfaces to be milled are aligned in a.single plane 'and can be milled in a single pass. Multiple-piece rotaryfixtures-for continuous milling (Fig. 134) are also used with a gang oftwo milling '~utters. One cutter mills the main flank and the other,the ..'aux ili ary flank. The final shape specified by the drawing isimparted to :'the point during sharpening and lapping. As a rule,·single-point tools are sharpened hv offhand grinding methods'.'SPeei~1 semiautomatic tool grinders 'a"'e also available that ensurehigher quality in' tool sharpening. '

'j.'. .. .

f

,t- rfgJ

_ E~jf~§~

f-.rt,~~f Fig. ,134. Multiple-piece fixture fOT the continuous milling of .~' tool flanks'-

Standard Cu.tting Tool Manufacturing Processes------- '--------Of especial interest .in single-point tool production are the opera­

Lions for making the tool point which may consist of closed-die­forging, smith forging, milling or grind ing. Depending upon thecOI1stl~uctionof the tool, forging is done in one or several die impres­sions;; In a bent-shank tool, the point is first bent over and then thefluI1:ks arc forged and the flash is trimmed. Forging the tool point inspeCial: dies is a highly productive procedure used in mass and large-lot; production. . . .'-

In manufacturing comparatively small lots, the tool points are'_, produced by milling. Multiple-piece fixtures for the simultaneous

-Z2-

'~5):cleaning the blanks in a sandblasting machine;'(6) and (7) butt welding and annealing;'(8) snagging off the flash at the weld;(9) straightening the welded blank;

(10) facing the end of the shank;(,11) drilling and countersinking the centre hole In the shank

(Fig. 135a);(12) turning the external centre on the point; ,(13) rough and finish turning the body on the outside diameter

(Fig. 135b);(14) rough and finish turning the taper of the shank (Fig. 135c);(15) turning the shank at the tang and facing the end;(16) milling the tang (Fig. 135d); /. (17) milling the helical flutes (Fig. 135e);(18) milling the body-diameter clearances (Fig. 135!);(19) heat treatment and cleaning in a sandblasting machine;(20) polishing the helical' flutes;(21) grinding the centre hole and external centre;(22) grinding the taper of the shank;(23) grinding the body over the margins with the required back

taper (Fig. 135g);.(24) sharpening the drill point (Fig. 135h);(25) inspection and marking. ,The external centre and the centre hole are the location datum

surfaces, in machining twist drills. Therefore, the centre hole isdrilled and countersunk at the end of the shank, and the externalcentre is turned on ,the other end in the initial stages of manufacture ..The first operation following heat treatment is the grinding of thecentre hole and external centre. The most 'specific operations indrill manufacture are the milling of the helical. flutes and body-diameter clearances" and drill point sharpening. .

Since these tools are usually produced on a mass scale at toolplants, the flutes and body-diameter clearances are machined. inspecial semiautomatic or- automatic machine tools. Semiautomaticmilling machines may be intended for mflling one flute, a flute' and:a body-diameter clearance, or both 'helical flutes. and hoth body-:diameter clearances simultaneously. In the -toolrooms of engineer­ing plants, helical flutes .and body-diameter clearances are milledin universal milling machines. Special' form milling cutters ,':are'used for the flutes. The body-diameter clearances of drills over 12 mmin diameter are milled by a form cutter, end mill, side milling eut-,ter, or a ··tapered cutter. The hody-diameter clearance of' smallerdrills is machined by grinding. . ' ..: " , " ' " ,, . The body isgroundoverthemargins with the required hack taperin a universal cylindrical grinder or in a :.gentreless grinder by the

"

'.'!l

. '. 2. Taper-Shank Twist Drill Production

, " '(1) the cutting: lips .must he .0'£ equal length and symmetrical in, " reference, to '~the.' 'dri ll. axis; .. , " ,,' ',',' ' , ". ,,': j2Lthe 1ip'}~Hefa:t;lgie~,-:point'_angle, and chisel-'edge' angle must be. 'equal to the rec'oinniend.:~d,values. ''/' ' , ,

: I.

rg)

'Fig. 135: Principal operations in machining twist drills

(/1)

(d)

r"

(en

(C)

infeed method using a grinding wheel' trued to the required taper.The following cond it.ions must be observed in drill sharpening:

~ St(t.ndar~utting Tool 11[anujactuTing Processes

:~-~,I,j!,

f1tLfIt~.

:3. Carbide-Tipped Shell End Mtu Production

The manufacturing process for shell end mills with cemented­carbide: tips brazed directly to the hody consists of the followingsequence. of operations:

(1) cutting off the hlank;(2) roughing in a lathe: facing one end, drilling and enlarging

the hole, turning the outside diameter, boring the recess,facing the bottom of the recess, turning the clearance groovein the recess, core drilling and reaming the hole, turningthe outside diameter from the other end, and facing theother end (Fig. 13Ba);

(3) finishing in a lathe: turning the outside diameter, turningthe shoulder, facing the end and shoulder, and chamfering(Fig. 136b); . /

(4) milling the drive slot on the rear face and burring (Fig. 136c);(5) milling the slots for the tips (Fig. 136d);(6) and (7) milling the flutes on the periphery and face of the

body (Fig. 136e);(8) and (9) milling the tooth clearance surfaces on the periphery

and face of the body (Fig. 136/);(10) removing burrs and inserting the tips;(11) brazing the tips and heat treatment;(12) cleaning in a sandblasting machine;(13) rough grinding the carbide tips on the outside diameter

(Fig. 136g);(14) grinding the mounting hole and mounting. (rear) face

(Fig. 136h); . . .(15) grinding the teeth on the periphery and end of the cutter;(16) grinding the bottom of the recess; .(17) grinding the Ilutes on the periphery and face, grinding the,.. tooth faces (Fig. 136i); ... - -..(18) grinding the relief surfaces (relieved lands) of the teeth on. the periphery and face, grinding the chamfer and its relief

angles (Fig. 136j);. .(19) grinding the back of the teeth on the periphery, face and

chamfer (Fig. 136k);(20) lapping the tooth faces, the relieved lands on the periphery

and face, and on the chamfer (Fig. 136l);(21) inspection and marking.

i _

~-

.Offhand drill sharpening cannot. meet these conditions. Correctdrill geometry and a high quality of the ground surfaces can be eu­sured only if drills are sharpened in special grinders or attachments.

. Carbide-Tipped Shell End 1'vlill Production

Fig. 136.: Principal operations in machining shell end mills"

(I)

(i)

~l2fCT

(e)

(g)

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t EEh g~,

r

~

:-

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,. --

ZIJ'

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19-1275

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4. Spline Broach Production

Spline broaches are manufactured by a process consisting of thefollowing sequence, of operations: ,

(1.) and (2) cutting off the blanks for the shank and cuttirig sec--tion of the broach, preparing them for welding (Fig. 137a);

(3) and (4) butt welding and annealing(. -(5) snagging off the flash at the weld;(6) straightening the welded- blank;(7) facing and drilling centre holes at both ends (Fig. 137b);(8) lathe operation: turning the outside diameter, front pilot,

rear pilot, neck and pull end; and the taper of the cuttinglength; laying out the tooth pitches and turning chip spacesof the teeth (Fig .. 137c)j- -. - - - ':

(9) milling the splines and 'cleara,nce· grooves at· the roots of. the splines (Fig. 137d);. (10), (1~) and (12) heat treatment, straightening and cleaning in

a .sandblasting machine; -(13) grinding the centre.: holes; __(14) roughgrinding (sharpening) tooth faces a-nd hacks of teeth

(Fig. 137e); '.(15) grinding the _front pilot, _pull end, neck and taper of the

frontpilot.itaper of the cutting teeth; outside diameter of the- finishingteeth and the rear pilot (Fig; 137f);

(i6) final 'sharpening -by grinding the tooth faces and lands(Fig. ,137g);

,'.),r"".,~I-

The special featrues in the manufacture of these end mills, .aswell as similar carbide-tipped tools, are the operations for preparingthe slots, brazing the tips and subsequent machining such unlikematerials as the cemented carbide and the steel of the body.

Due to the high cost of the cemented carbide and its lower machin­ability as compared with steel, the manufacturing process is plannedso that the tips will be machined with the least possible allow­ances. Much higher forces are developed in grinding the cementedcarbide than in grinding the steel of the body. For this reason, ifthe tip and body are ground at the same' time, the sizes measuredover the carbide tips and the steel body will- differ, because of thedifferent deflection of the grinding wheel. This drawback can beeliminated by using a grinder with higher rigidity or by grindingthe tips and body separately. Cemented-carbide tips are to be groundwith a green silicon' carbide wheel, and the body with an aluminiumoxide wheel. Such separate operations are applied in cylindricalgrinding and in grinding the tooth faces and relief surfaces forsharpening.

Spline Broach Production.

(i)

,::Fi'g:.1'37"\:P~'i!lcipal opcr~tions 'in machlnj ng spline Dro~ches• +" " •• ' '.. : °i' . . . . :.

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5. Gear Hob ProductionGear hobs with a straight-line profile in 'a 'normal section; and

with a module m>2 mm are manufactured by a .process consistingof the following sequence of operations: ' .

(1) cutting' off the blank (Fig. 138a);(2) forging, annealing and pickling;(3) roughing in a lathe: facing the ends, drilling the mounting

hole; 'rough turning the outside diameter and hubs, boringthe recess and chamfering the hole at each end (Fig. 138b);

(4) broaching the mounting hole (Fig. 138c);

,..• It,/,.f -:, ,

(17) grinding the splines (Fig. 137h);. (18) grinding chamfers and chip-breaking notches on the splines

(Fig.. 137i);(19) inspection' and marking. ' ,Centre holes serve as location datum surfaces in internal broach

manufacture. Since a broach is usually a tool of considerable length,steady-rests are used in machining. Specialfeatures in the productionof internal broaches and , particularly, spline broaches are the oper­ations concerned with the machining of the teeth: turning thechip spaces, milling and grinding the splines, and grinding thetooth faces and lands (sharpening). The teeth (chip spaces) are roughedin a lathe with a form tool of a profile corresponding to that of thechip spaces. Before turning the teeth, their pitches may be layed outwith a special tool, gang of circular tools or, for a large pitch, a cut-offtool. The circular tools with intermediate spacer collars are assem­bled on a single arbour at distances equal to the tooth pitch. Ifa cut-off tool is used, it is traversed from tooth to tooth throughdistances equal to the pitch by means of gauge blocks inserted be­tween a stop on the bed and the carriage. The teeth are layed outbeginning with the finishing teeth and ending with the roughingteeth. The splines can be milled by various methods. The sides ofthe splines can be straddle-milled with single-angle cutters andthe spaces between the splines with a radius form cutter. Narrowspaces (up to 5 mm wide) can be milled with a slitting saw. Higheroutput is attained by milling the whole profile of the space witha form milling cutter.' ,Following heat treatment, the sides of the splines and the spaces

can be ground separately. The most widespread method, however,is to grind the. whole profile of the space with a formed wheel ina spline grinding machine. In broach sharpening I the tooth facesare ground with the tapered side of the wheel, while the lands areground with the periphery of a straight wheel.

..:

Gear Hob Production

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i"hi.-138:--:.p~i~Ciparope~ationsin machining gear hobs~ . . . .

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:6.. Disk- Type Spur-Gear Shaping CutterProduction /

The following sequence of operations is used for manufacturingdisk-type gear shaping cutters:

(1) cutting off ·the blank;(2) forging; 'annealing and pickling; ,

(5) finishing in a lathe (on a mandrel): turning the outside di'am­et er , turning the hubs and chamfering, and facing the hubs(Fig. 138d);

(6) :broaching the keyway and chamfering (Fig. 138e);(7) milling the worm threads (Fig. 138/);(8) milling the helical flutes (Fig. 138g);(9) relieving: turning the' first relief surface, turning the second

relief surface (Fig. 138h);(10) removing incomplete teeth at the ends of the hob (Fig. 138i);(1) heat treatment and cleaning in a sandblasting machine;(1.2) grinding the hole (Fig. 138j);.(13) lapping the hole (Fig. 138k);(14) grinding. the hub faces (Fig. 138l);(15) grinding the tooth faces (Fig. 138m);(6) grinding the tooth profile and hubs (Fig. 138n);(17) chromium-plating or cyaniding;(18) inspection and marking.Specific operations in hob manufacture are the milling of the

threads and helical flutes, relieving and sharpening of the hob.The threads should be cut, flutes milled, and relieving should bedone on several hobs mounted on a single arbour. The blanks shouldbe arranged in the same order for all three indicated operations.The hobs may be relieved in three operation elements, relievingthe sides of the thread and top separately. When hobs are made inlarge lots, tools for relieving the whole tooth space profile are used.This principle of increasing the zone of contact of the cutting toolelements and blank to increase the output is also applied in relief­grinding the tooth profile with a wheel trued to grind both sides atthe same time (Fig. 1380). Truing and dressing such wheels andtheir operating conditions are more complex than for wheels thatrelief-grind the elements of the profile separately. Before grindingthe tooth profile, the tooth faces of the hob are ground. The hobsharpening machine in which the tooth faces are ground, and. therelieving lathe for grinding the tooth profile must be set up to exactlythe same flute lead value as otherwise taper of the hob is inevitable.The hob tooth profile is checked with template-gauges in a toolmaker'smicroscope or in other special instruments ..

. Disk-Type Spur-Gear Shaping Cutter Production

. .~~.~::..:j'(:..-;... :.::....~.::·~.;Z··.:·. '. .. . :'. . . . . . . . . . . .WherE(b ':::"~':ho.b':~trav.el,fronlthe face of the 'cutter parallel to' its axis

, 'at':," "r'eli~f.atthe top- of the' teeth {outside angle) ...,. '.' .. :' .

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,,_)'tandard Cutting Tool Monu iactu ring Processes,--

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(3) roughing in a lathe: drilling the hole, facing one end, roughturning the outside diameter; facing the other end, roughturning the outside diameter from the other end (Fig. 139a);

(4) finishing in a lathe: boring the hole and count.erbore, reamingthe hole, Gutting the clearance groove and chamfering atone end of the hole (Fig. 13gb);

'(5) turning the cutting face (Fig., '139c);/(6) turning the outside diameter to a taper (Fig. t39d);, (7) turning the chamfer OIl the mounting face and chamfering"

at the other end of the hole;fR\ hobhinz the teeth (Flo' l';:{Qp')"\'-'1 J" ' - t.A, b ,1·.....~·v_, - \ ~O· t.J~v 1

(9) heat treatment and cleaning in a sandblasting machine;(10) grinding a land on the cutting face and grinding the mounting

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(11) lapping the mounting face, (Fig. 139g);(12) grinding the hole and the retaining face (Fig. 139h);(13) lapping the hole;('14) rough sharpening (rough grinding the cutting face);('15) rough grinding the tooth profiles on each side of the teeth;(16) finish grinding the, tooth profiles (Fig. 139i); ,(17) grinding the outside diameter to the outside angle (Fig. 139j);(t8) final sharpening by grinding the cutting face (Fig. 139lc);(19) grinding the chamfer (Fig. 139l);(20) -chrorni urn-plating or cyaniding;:'(21) inspection and marking.Specific features of shaping cutter production are the hobbing and

j' generation grinding of the teeth. The teeth may be cut with a gear~ -hch in a gear hcbber: In this case, the cutter relief angle is obtained

by a combination of hob feed along the axis of the cutter and radialinfeed of the' hob. To obtain a definite relief angle, there must be'a kinematic: 'linkage between these two, feed motions. This 'can be

f, achieved by changing the gearing of the gear hobbing machine and,t: 'in certain cases, by adding a change-gear' quadrant to the gearing.

If such, a' modified machine is not available, the teeth of the cutterl ''C~ri be hobbed in' an ordinary gear hobber with the aid of hand radialt .inleed.: In this' case, hobbing is performed at first in the same way as

for an ordinary spur gear with feed parallel, to the gear, blank axis.Wheri the' hob is 2 or 3 mm from the mounting (rear) face of thecutter, the feed is.._disengaged and the blank is advanced by hand inthe direction of the radial infeed toward the hob axis. The amount,df this manual .Infeed is

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Fig. 139. Principal operations in machining gear shaping cutters

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the slide and counterweight. are denoted by 1 and 7, respectively).The side of the grinding wheel, in the same manner as the side of arack tooth, will occupy a series of consecutive positions in relationto the cutter; the enveloping surface of these positions is the requiredinvolute profile of the cutter tooth. The tooth profile can also beground with a grinding wheel on which a helical worm thread hasbeen trued. This principle is based on the meshing of an involute wormwith the cutter and is similar to hobbing the cutter with a gear hob.This method is chiefly .used for grinding fine-module cutters. 'The following elements of shaping cutters are inspected: profile

on the sides of the teeth, circular pitch and accumulated pitch error,pitch' circle runout , and deviation or the tooth addendum Irorn thetheoretical value for the given .tooth thickness. ' . ' :

Fig. 140. Generation grinding of the tooth profile on a gearshaping cutter

This method is less accurate and productive than the precedingone hut practically it provides satisfactory results.The profiles of the cutter teeth are ground by the generating method

in a special precision gear grinder whose principle of operation isshown in Fig. 140. Cutter 3 is mounted on arWUT:2 on which involuteearn 5 is also rigidly mounted. Upon rotation of the arbour, the cam,bearing against positive stop 6; 'will move the centre of the shapingcutter along guides. As B. result, the cutter will have a generatingrpotion in reference to the fiat side of 'grinding wheel 4 (in Fig. 140

S tandar d Cutting Tool .Manu jacturing Processes

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1 Making Form ToolsComplex-shape surfaces are surfaces with the cross section outlined

by curves or broken lines. In cutting tools, these surfaces can bemachined in two 'ways: with a conventional cutting tool performingthe required curvilinear movement controlled with template devices;.and with form tools. Tool complex-shape surfaces are producedon conventional and relieving lathes, milling, grinding, sharpening,and optical profile-grinding machines.Form tools oyer 100 mm wide are turned on lathes using templates.

A conventional single-point tool is employed as a working tool.Form milling cutters up to 100 mm, and, in some instances, up

. to 200 mm wide are turned with end (shank-type) form toolssimilar to those shown in Figs. 132, 134, and 135. After turningthe profile of a cutter, flutes are made, and then, the profile isrelieved with end form-relieving tools.

Profile-sharpened and form-relieved milling cutters are used inmany fluting applications (e.g. cutting flutes' in drills, taps, reamers,etc.). Profile-sharpened form milling cutters yield substantiallyhigher production rates, hut their manufacture and sharpeningrequire special machines and fixtures. The tooth profile on profile­sharpened cutters is ground predominantly with form grindingwheels. The specified profile of the grinding wheel can be obtainedby truing with a form crush roll or a diamond mounted in specialdevices. .A form crush roll, shown by way of example in Fig. 144, is a cylin­

drical body with a profile corresponding to that of the workp-iece.It is made of steels, Grades "Y12A,9XC, X, X12M, or P6M5, andheat-treated. For' better tearing of abrasive grains out of the bond,slots with uneven spacing are cut over one-half or one-third ot"thecrush-roll circumference. Uneven spacing of the slots makes, aswell as in reamers, for improved work surface finish. Truing theform wheel profile is done by rotating the crush roll manually Offrom an electric motor at a peripheral speed up to 15 m/min inengagement with the wheel, the drive of the latter being disconnected.The' crush roll is mounted on a mandrel between centres.

~

Sharpeningof

Cutting Tools

q5

(here, convex) is shown in Fig. 149a. The device is placed on a sharpen­ing machine. In operation) an upper slide carrying a head that holdscutter 2 being sharpened is rocked manually to 'the left and to theright about axis O. Each point of the cutter half-round profilemade to radius R should lie on a line that intersects the axis theupper, slide is rocked about. Thin solid lines show the extreme posi­tions ·of grinding wheel 1 at points A. and B. Non-symmetricalmilling cutters are profile-sharpened in the device shown in Fig. 14gb.The device is operated by rolling a template. on a stationary bar.The, position of the cutter to be sharpened is adjusted so' as to bringthe: 'cutter profile into coincidence with that of the template. Asthe, .Iatter is rolled, the cutter will receive the specified shape.·Template 4 is secured on the underside of swivelling plate, 2

which 'can be swivelled to the left or to the right about its axis byhandle 6. The movement of plate 2 will result in rolling template 4on ,~~st bar 3. Plate 2 is mounted on slide 1 moving along' rol lingguideways 7. The slide is urged by spring 5 through the templateto the rest bar. The plate carries a fixture wherein the cutter :;1;0.be sharpened is mounted on a mandrel. The projection of the cutter'shm.;Ildbe aligned with the template contour. A substantial drawback

..

Fig: 1A8. Truing devices for grinding wheels with symmetrical profile{a) . convex; (b) concave

(a)\ ,

Figure 1.48a. and b shows two truing devices, mounted in suitableholders, for wheels with respective symmetrical convex and concaveprofiles. In the process of grinding, the work pieces will be shapedcoilvetsely. The diamonds are rocked with a handle. After truing,the device is removed from the machine. /, Methods of sharpening form milling cutters differ radically depend­ing on whether their contour is symmetrical or non-symmetrical.A'shat-pening device for a milling cutter wi th a symmetrical profile

_--- .iHACHINING METHODS

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Tool SharpeningSharpening is a method of grinding the cutting surfaces of tooh

to the required angles. One of the final operations in the procesiof manufacture of cutting tools, it is very important as it has a'majoieffect on the tool performance and service life. Cutting-tool sharpening methods and equipment are numerous and varied. 'Lathe tool sharpening. High-speed steel lathe tools are usee

where cemented-carbide tools are unsuitable. In cutting-tool production, high-speed steel tools are applied to profiling, relievingthreading, and cutting-off on automatic ana semi-automatic lathesForm tools are made largely in shank type, although circular .andstill more rarely, dovetail types are encountered. Shank-type forntools (lathe and relieving) come with a zero rake, which substant­ially simplifies their manufacture. For instance, the profile of forntools is obtained with manual finishing or grinding. on profile grinders. Sharpening and resharpening the tool face is done on surfacegrinders.

grinding the profile of carbide form tools. Consumption of diamond:on such grinders is not high owing to the use of narrow abrasivtwheels 10.

-"~1

Fig. 150. Diagram of optical system for profile grinder

This machining technique provides for high accuracy of thproduced profile. The machine is easy to handle as the screen jlocated in front of the operator. Here, the operator's fatigue aneye strain typical of the work on profile grinders fitted with micrcscopes are eliminated. These machines are particularly suited t

~-:;

CR. 3. MACHINING rrIETHODS

2.5-°,and particularly, ralieving tools. The grinding wheel on a profilegrinder can be set to an angle of +100 for forming the ,end-cutting­edge angle. The maximum width of the surface to be machined,determined bv the wheel cross traverse, should not exceed 48 mm.An Improved optical profile grinder, Model 395~I, features a screen

which allo-ws the operator to view the contour being ground wi thouteyo strain. In thiamachine (Fig. 150),' a light beam from source 1falls onto inclined reflector 2 which directs the beam to workpiece 3.From the workpiece, light rays are 'reflected back and, passingthrough diaphragm, 4 in the reflector and through illagnifying lenssystem S, are projected as a direct image onto mirror 6. The latterreflects the beam onto glass screen 7. Profile 8 'of the workpieceis viewed as a -sharply outlined dark image on the bright screen.The profile template to a scale of 50 : 1 or smaller is fixed. on

the, screen in the operator's field of vision. The workpiece contourimage is projected in the course of grinding onto the template con­tour, and this enables the operator to see what sections of the work­piece profile are coincident with the specified contour 1 and :whatamount of stock allowance 9 still needs to be removed.

FIg, i49. Cutter sharpening devices(a) for svmmetrtcal-prottle cutters; (0) for non-symmetrical profile cutters; (c) positioningbot h types ot cutters

(c)

" ,.4 =::. ;::J'~sino;2f

of the device is that the template profile or the rest-bar surfaceerrors are transferred to the profile of the cutter on ,an 1 ~,1 scale;which leads to distortions in the shape of smaller cutters. ~ ",,",'To overcome this problem, S. Kutko has developed a: device

which allows cutter profiles to be ground to a 50 :' 1 scale.In tool production; curvilinear surfaces on templates and forming

tools (straight and circular) are machined on optical profile grin­del's. These machines can handle tools with relief angles' of 'up to

MAKING F01U1 TOOLS

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manual becausemachine sharpening involves impacts of tools againstthe grinding wheel, which results in cracks on the carbide insertsdue to their low impact strength and non-uniform structure.Tool sharpeners, or grinders, come in single-, two-, and even

thre.e-wheelhead types. Each wheel spindle is driven from a separatereversible electric motor. A tilting table that can be inclined toa desired angle 'within the range of +150 of arc is located in proz­imity to each grinding wheel. Such machines are built with either

/.

Fig. 152. Single-pointtool sharpenedwith diamondgrinding wheel

en6Fig. 15t. Sharpener for single-pointcarbide toolsl-reciprocating abrasive wheel:2-tool being sharpened; 3~swivemngwork holder; 4-fixture body;5:_template; 6-rest bar; 7-tilting

. table

In the updated metalworking industry, extensive use is madeof Iathe tools with indexable carbide inserts, which offer consider­able advantages over bra-zed carbide tips' and are gradually oustingthem. Lathe tools are mostly furnished with triangular and squareindexable inserts.Shank-type lathe tools have found the widest application in

metalworking. They are .sharpened on tool-sharpening machines ,.._especially fitted to this type of tools (Fig. 151). The operation' is

. TOOL SHARPENING

It

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A -A (reooioed and ell/ur!Jed),az-as

wheals or work tables performing reciprocating movement. In bothcases the workpiece (a tool) romains stationary. The reciprocationis imparted to the wheel or 'to the table at a frequency up to' 120strokes per minute with a length of stroke up to 30 mm., Such a type of tool sharpeners can be exemplified by the .modsl3B632B. The machine is used for sharpening lathe tools of improvedaccuracy with a size up to 50 mm". The work table is .provi ded withlongitudinal slots to' receive fixtures for better guidance of thetool' being sharpened with relation to the face of the grinding wheel.The wheel spindles of such machines should be very rigid and runwithout vibrations. The reversible motor makes it possibleto sharpenboth left-cut and right-cut tools, and also grind, for instance, themain flank and the auxiliary flank of a right-cut 'single-point toolon the left-hand and the right-hand sides 01 the wheel, respectively.Axial runout of the grinding wheel should not exceed 0.025 mm;larger runout leads to rapid wear of the 'wheel and coarser work surfacefinish:

Sharpening a new tool begins wi th grinding the tool shank toa specified relief angle Irom the carbide tip down. A tool shaped tothree Io llowing relief angles is advantageous (Fig. 152): the first,a, made over a tip margin of '1.5-2 mill high; the second, [a + (2-3°)],over the rest of the tip; and the third, fa + (4-6°)], over the toolshank. The relief angle on the tool shank is made first. Sharpeningis carried out with the periphery of a Flfl-type wheel or, for speedingup the operation, with the side edge of a cup wheel made of abrasivem-aterials, Grades 8 or R31 with a grain size of 25. Rough grindingof 'the carbide tip is done with the face of a diamond cup wheel,which features a constant peripheral speed throughout its wholeservice life regardless of wear. The wheels used, are vitrified-bondeddiamond wheels with grain sizes of 160/125-125/100.-Finish sharpening is done by diamond wheels with grain sizes

of 1.00/80-50/40 to obtain the 9th and 1qth classes of surface rough­ness. Vitrified-honded wheels with a grain size 100/80 have comeinto use for sharpening Large-size roughing tools. They providefor the 8th and 9th classes of surface roughness. The 10th and ;11thclasses are obtained on tool cutting edges with the use of -vitrified-'bonded diamond wheels having a grain size of 63/50-40/28.

For rough sharpening or lathe tools" use is made of ATIB-typecup wheels 250, 200, and 150 'mm in diameter (depending on thetool size),' and for finish sharpening, identical. wheels 150 mm indiameter. Hough stage begins with processing the carbide tip face;main and auxiliary flanks' follow. Finishing is. performed in thesame sequence and ended with rounding the nose. ', To prevent crumbling-out the carbide tip, it is advisable to; movethe' grinding wheel from the tip to the shank (although it IS' not

• always practicable). In the course of sharpening, the tool should

ca. '3_'MACHINING: :METEODS

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f

rf

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.be .moved continuously with 'respect to the face of the wheel. .:Th~chip-breaking groove. should .be ground prior to finish grindingof the main and the auxiliary flanks. The .operation is effected ona general-purpose sharpening machine or a surface grinding machine­by .means of a. ·vitrified-bonded wheel with a grain size of 100/80-and 63/50 or an organic-bonded wheel with a grain size of 100/80.. For increasing wear resistance of tools used in steel-cutting app lica­tions, it is recommended to hone their cutting edges and nose toan angle of 45° with an abrasive stick. Such an operation producesa margin not over 0.1 mm wide and smoothes surface micro-irregula­rities. Honing is done with K3-type abrasive sticks having a grainsize of 4 or vitrified-bonded diamond sticks with a grain size of40/28. The cutting conditions in lathe-tool sharpening are: peripheralspeed of diamond wheels, 25 to 30 m/s; stock removal per pass,0.01 to 0.015 mm and 0.005 to 0.008 mm for rough and finish grind­ing, respectively; rates of feed of tools relative to the wheel facein rough grinding, 1250mmlmin, and in finish grinding, 600mm/min.Tool geometry is checked with bevel protractors, special instru­

ments, or contour gauges.The process of sharpening twist drills consists in relief grinding

the tool flanks to conical, helical, or flat shape.The following requirements are placed on sharpened drills: point

angle 2q>should be held within the specified limits; relief angle·on' the cutting edges (lips) should be maintained over their wholelength; both the lips should be equally long;. the drill axis' shouldpass through the middle of the chisel edge; runout of the lips relative­to the shank should not exceed the prescribed value.Relief grinding of twist-drill flanks to conical shape is usually

done by the off-hand method. The machine grinding is rather rare­in batch production because the automation of the process presentssubstantial difficulties. Therefore, shaping conical .flanks on twistdrills is not treated in this book. At the same time, automatics­and semi-automatics are extensively used for grinding the twist-drill flanks to helical shape. .Relief grinding of twist-drill flanks to helical shape. For this opera­

tion on drills 10-80 mm and 3-15 mm in diameter, use is made ofspecial semi-automatics (e.g. Model 3659M) and automatics (e.g.Models 3fS2 and 3f~52}l,), respectively. -A helically-shaped flank results from complex movements of

the grinding wheel with relation to the drill being sharpened. Figure·153 shows the principle of such a sharpening machine. The drillto he ground is clamped in a chuck and set in rotation in the direc­tion of arrow a. Grinding wheel 1, along with rotation about axis I to

shown by arrow b, performs two more movements: -(a) turning about axis I I in the direction of arrow c for oscillation

of its c~tting surface along the drill lip; this is achieved by an eccen-

• j

,

., TOOL SHARPENING

- 100-

'f~om 3 to 80 mm in diameter are ground flat, the former being pro­.cessed manually on grindstones and the latter, on plain and "semi-automatic tool grinders [3], ", Straight and taper-shank twist drills 6 to 80 mm in diameterare made with the flanks ground flat. The shape of the flank isshown in Fig. 155a. The relief angle value on margin f ranges'. from5:to 15° depending on the material drilled. The second angle ranging, from 25 to 35° and over is made to prevent the end of the land from~nterference with the bottom of the hole being drilled at point c.

Fig. 154. Drill-point contourgauge

Figure 154 shows a combined contour gauge used for checkingtile point angle (Fig. 154a), the relief an~e (Fig. 154b), and thechisel edge angle (Fig. 154c). The flanks ...on drills up to 3 mm and,

Fig. 153. Grinding drill point for helical shape of flanks

trical arrangement of wheel spindle axis I relative to axis II of sleeve.2 in which this spindle is mounted, rotation of the sleeve beingindependent of that of the wheel spindle; and

(b) axial reciprocation (in the direction of arrow d) controlledby cam 3 rigidly secured on sleeve 2 and urged by spring 4 to stop'pin 5., .The point angle, the chisel edge angle, and the symmetry of the

. lips are checked with various types of contour gauges.

MACHINING METHODS

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Fig. 155. Setupfor sharpeningcarbide-tippedtwist drill

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Sharpening a drill with conical lip relief surfaces

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Fig. 156. Web-thinned twistdrtl lpoint

The second angle is also made on carbide-tipped drills and solidcarbide drills. Flanks of drills under 3 mm in diameter are groundflat. '.Figure 155b shows a diagram of grinding a carbide-tippeddrill with a taper shank. The operation is carried out on a general­purpose tool grinder. Drill 2 is inserted into the tapered hole ofthe tool holder. The flanks are relief-ground separately by diamond

wheel 1with a grain size of 100/80.Land a being ground is held in posi­tion with the help of rest finger 3. Toobtain the specified relief angle ingrinding with a cup wheel the follow­ing conditions must be met: (a) thelip on each flute is orientated withrespect to a horizontal plane; (b) thedrill axis and, hence, ,the work-holderspindle are set to angle '9 relative to

, ,-the horizontal; (c) the drill axis and,accordingly, the work-holder axis areset to angle lP with relation to thewheel face. This sharpening methodallows the lip runout to be held within0.08 mm.

Web thinning. Axial thrust in dril­ling C9.n be reduced by thinning the webwith simultaneously shortening thechisel edge. Figure 156 illustrates twovariants of the chisel-edge shortening.The first variant is represented: byblack areas. Here, thinning takes Q.2to 0.25 the lip/length; it extends :tothe second flank and reduces the

chisel edge from AB to A'B'. By the second variant, shown withdotted lines, the lip becomes slightly inclined to angle 1P to theleft and to the right of the chisel edge, extending to the secondflank. As a result, the chisel edge is shortened from AB to A/B'.Web thinning does .not weaken the chisel edge. The thinning

area extends along the drill axis over 5 to 1'5mm depending on thediameter and is ground on special machines after each sharpening 'orafter two or three sharpening operations. These machines are simplein design and easy to handle. Web thinning is advisable for drillsover 10 mm in diameter. -. ""S~arpening milling cutters, taps, reamers, and core drills. Sharp­

ening techniques differ for various cutting tools depending 'onwhether they are form-relieved or profile-sharpened, have straightor helical flutes. The basic requirement for form-relieved cutting'tools is that the top surfaces of the sharpened teeth be equally dis-

CR., 3. MACHINING METHODS

--~;

1f:

automatic, Medel 3662. Semi-automatics are also used for sharpeninglarge hobs. To grind the tooth faces along helical flutes, the machineis set up for the lead angle and pitch of the flute. Here, the grindingwheel goes out of the flute completely on both sides in the courseof operation. The hob is indexed one tooth for each double strokeof the wheel. The tooth faces of finishing hobs should be disposedstrictly in a radial plane. The rake angle is checked by means ofa special instrument.Hobs of accuracy classes A., AA! and .I.A.AAare ground on plain

mandrels. Types of abrasive wheels used for rough grinding are2A, K, 40, CM1-Cl\12, and for finish grinding, 2A, K, 25-16, andC1-CM2.

Taps are ground on the face surfaces (Fig. 157d) and on the cham­fered portion of the land. For grinding the face surface, use is madeof semi-automatic tool grinders with automatic indexing by meansof an index plate. In small-lot production, the operation is doneon a universal tool grinder with the aid of a supporting finger restingagainst the heel of the tooth being ground in a similar manner asshown in Fig. 157a. To form the rake on the tap' face surfaces, themachine table is set off with respect to the cutting edge ..by an amount

rr D.. 8)ts=2 Sl.ll ('V+

tant from the tool axis. To this end, the tooth faces are groundon semi-automatic machines with the help of index plate 2 andindexing plunger .1 (Fig. 157a). In small-lot production, the toothfaces can be ground on a hand-operated general-purpose tool grinderas the backs of cutter teeth bear up against' supporting finger 3(Fig. 157b). In off-hand grinding, the wheel is not withdrawn fromthe flute. Grinding the tooth faces is done preferably with the con­ical surface of types 4II Of 1T grinding wheels (Fig. 157c). In thisway, better surface finishes can be obtained.

Sharpening gear-cutting hobs .50 to 125 mm in diameter withstraight and helical Ilutes is carried out on a tool-grinding semi-

10-20°

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1-, TOOL SHARPENING

10 L

by cams. The tap is placed between centres and ground with a wid e. wheel along the whole chamfer length. The wheel employed ha s. a grain size of 25 and a hardness of CM1-C'N12.

The rake angle in taps 5 to 52 mm in diameter is checked ona special measuring device (Fig. '158).

Setting standard 3 is placed between centres in such a \1..(aythatits datum surface lies in vertical plane AB .z'I'he face portion of thecontact tip on measuring lever 2 is brought into contact with a side.of gauge-block set 5 whose opposite side rests against the datumsurface of the setting standard. The second arm of the measuringlever contacts the measuring plunger of a dial indicator. Th~'setof gauge blocks is equal in size to the distance from the centre oftap 4 to the point where the face surface joins the fillet of the flute(the tip of the measuring lever is to touch the face surface in .thatpoint). The distance is found from the formula :.. x=R-b

where x = size of gauge-block set.R = tap outside diameterb = specified distance from tap outside surface to c-ontact

point in radial direction

Fig. 158. Checking tap rake angle

"where D = tap diameter, mm'Y = tap rake anglee = disc wheel profile angle (Fig. 157e)

Used for sharpening are grinding wheels of Types 4II or II', 2A,It, 25, and CM1. The face surface ground as is shown in Fig. 157eexhibits the best ·surface finish.

The chamfer of a tap is relief-ground on a special grinding machine.or.« cylindrical grinder using a special relieving device controlled

'. MACHINING METHODS

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Grinding profile-sharpened milling cutters, reamers, and core drills­is done in the following sequence: first, the tooth faces; second,the outside diameter (on cylindrical grinders); and finally, the lands.

The tools are ground on the tooth faces by dish wheels. The setting­of the wheel for grinding the tooth faces on helical-flute milling­cutters is similar to that shown in Fig. 157c.

For grinding, reamers, core drills, and milling cutters are mountedbetween centres, and arbor-type tools, on a mandrel. The outsidediameter is ground to obtain the final size with the cutting edgesequally distant from the tool axis. The lands are ground with straight ·or cup wheels. In grinding with a cup wheel, the axis of the workpiece­is set to an angle. of 1 to 2° of arc with reference to the wheel face.In this. way, the wheel will operate with one edge only, and a cur­vature will arise on the land, though quite insufficient.

"~If

" fThe tangent of rake angle 1', and then the angle proper, are deterrn­ined for each flute using the specified value b and obtained value a.To find rake angle 'Y quickly, suitable tables are made up.

The chamfer relief angle is checked with a dial indicator (Fig. '159).The tap is placed between centres so that the measuring tip of thedial indica tor touches the relieved surface at a point. The tapisthen turned, and the readings of the dial indicator are noted at theland points nearby the cutting face and the heel. From the difference­of the readings and land width L at which the measurement has beentaken, we find

,­'!,'

Fig. 159. Checking tap reliefangle.' ,

Lower surface CD of measuring lever 2 is set flush with the lowersurface of stop 1 by means of a straightedge (the purpose of stop lis to locate the diametral point of the face on axis CD). In thisposition of the measuring lever, the dial indicator is set to zero.The setting being completed, the tap to be checked is mounted be­tween centres in place of the setting standard /and turned until the,cutting edge contacts stop 1. Now, reading is taken from the dialindicator and the measured value allows dimension a to be found.

.' . TOOL SHARPENING

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where D is the workpiece or wheel diameter in grinding with cup orstraight wheel, respectively.

A rest to support the tooth being sharpened should be Ioca ted'very near the cutting edge.The number of passes in sharpening is rated basing on practical

experience. Figure 161 illustrates circular-pitch, 'or tooth positionalerrors and also location of tooth faces relative to the axis in a form­relieved cutter after tooth milling.The following cutting variables are assigned for semi-automatic

.grinding of the tool cutting face:(a) for milling cutters and reamers., Sm ~ 3 to 10 m/min: iN··';_ 3 ,

to 4 (7th class of surface roughness); for taps, iN = 5 to 10 m/min-(8th class of surface roughness) depending on the difference in toothcircular spacing;'(b) .Ior form-relieved milling cutters, iN = 8 to 15; ,(c) for hobs with modules of 1 to 10 mm, Sm ~ 3 to 15 m/min,

.iN .. ,20 to 25t depending on surface finish and class of accuracyfor hobs (from AAA to C); five more passes per tooth are assigned .forspark-out; in sharpening with cubic born nitride wheels, the numberof ',passes is reduced. "In off-hand grinding of the tooth faces on profile-sharpened mi ll­

. ing cutters and reamers, the following cutting variables are taken:~for .tough grinding; s~ ~~ 4 to 10 mlmin and iN = 3 to.5; for Iinishgrinding, Sm = 2 to 4 m/min and i» = 2 to 3 (7th class of surface

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in tho operation with a cup wheel (Fig. t60a), and below the wheelaxis where a straight wheel is used (Fig. 16Gb). The amount A ofthe offset

Fig. 160. Milling-cutter sharpening methods

IJ,ttI

For grinding the land, a milling cutter or a reamer should be soposit.ioned relative to the wheel as to render the required shape ofthe land independent of the wheel wear. The cutting edge of thetoot.h being sharpened should be offset below the 'workpiece aXIS

MACHINING :i\IETHODS

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planes. The horizontal swivelling is required for sharpening flu t.broaches, and the vertical swivel ling, for setting the wheel to. thespecified angle when grinding the tooth faces en round broaches.

Sharpening breaches is first done on the tooth face and then, onthe land. Round broaches are ground while being' rotated betweencentres. Here, the grinding wheel performs rotational movement,.only, whereas in sharpening flat broaches, it reciprocates along thetooth faces of the broach held in a fixture which is located on themachine -table. Flat breaches can' be sharpened en conventio na I,too.l.grinders. '

The diameter of a grinding wheel used for sharpening round broach­-eson 'the tooth faces (Fig. 162) is found from the formula

'D = KDsiri (~~'Y) -: -:,__ tJJ~ • sin y. , : '; ,

roughness); Sm = 1.5 to 3 m/min and iN = 2 to. 3 (8th class of .sur­face roughness).

. In grinding the lands, the number of passes is specified at 2 to 4.Broach sharpening. The aim of sharpening a broach is to. restore

its cutting ability while maintaining the specified depth of cutper tooth. Broaches are sharpened on special. machines fitted .witha wheelhead that can be swivelled in both horizontal and vertical

View A

TOOL SHARPENING

10 Z

Fine FlnishlngFine grinding, sharpening, lapping, and polishing are used to

machine tool surfaces to a high accuracy and surface finish. >

Fine grinding is done at cutting speeds of up to 12 m/min and.a depth of cut of up to 5 !-LID with a subsequent spark-out 'stage.The latter takes a larger number of passes than the spark-o-ut· inconventional grinding and is continued until the spark has .complete­ly >died out. The traverse rate is specified at 0.1 to 0.3 the; wheelwidth. Fine grinding provides for the 9th to 11th classes of .surfacoroughness.

A grinding process may comprise roughing, finishing; fine grind­lng, and sparking-out. Where fine grinding takes place, roughing

2A, K, 25-16, ClVI1-Cl'tf2are used to grind the tooth faces in. broaches,and the lands are ground with straight wheel Type nIT.The position of a broach placed OIl the tool-grinder table is checked

with a dial indicator secured in the wheelhead. Checking the qua­lity of sharpening is made with universal measuring instrumentsand contour gauges, and by visual inspection. The depth> of cut.per tooth for round and flat broaches is measured with a micromete-r.Radial runout on the tooth cutting-edge diameter of a broach ischecked between centres with a dial indicator. .

Fig. 162. Setupfor grinding broachtooth faces

where D tVh = wheel diameter (not smaller than 40 mm)D = broach diameter measured on the first toothJ( = 0.85 = ratio of diameter at the broach cross section

where straight tooth-face portion joins the fillet todiameter D on the first tooth

p = wheelhead setting angle."1 = broach rake angle

The curvature radius of the grinding wheel should be smallerthan that of the broach tooth. Grinding wheels of Types 4n or 1T~

CR. 3.. MACHINING MET!!ODS

ff

-

The tapered face of the grinding wheel' is used in- sharpening a hob.by grinding the helical' tooth face. Such a wheel profile provides -for. practically satisfactory results only in sharpening hobs in ·whichthe helix angle (I) of the helical surface is .equal to or less than 7°.At .Iarger helix angles of the flutes, a ·t~pered-face wheel does not. produce a' straight, tooth face in the radial. direction. The departurefrom, a straight line of the generatrix of the flute, when the toothface is ground with a tapered-face wheel, can be determined withsome approximation by a method that was proposed by V. Shishkov, .

. Inspection, of Sharpened, Tools . . .Tool inspection. Iollowlng : sharpening implies ~easurin~· the

geometrical parameters. of the cutting elem~n~s; checking ~he dlre~- .sions'andprofile'''o~ the ~~:>olt",.and·dete~I;Illnlngthe quahty·o t e·sharpEm·ed-,:surfaces.' .

. .Fig. 129. Sharpeninga plain milling cutter with helical flutes

(1, ,', relief angleD . , .diameter of the' cutte..... . I

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.. 1

,UponLongitudinal travel of the table with the cutter, the cutteris turned by hand about its axis, tracing the tooth face in the flute'with which the tooth rest is in contact. The sharpening of such com­plex and precise tools as hobs requires the use of special machinesand attachments in 'which the .helical motion is produced either bymeans of a tracer bar or properly set-up change-gear quadrant.Twist and core drills are sharpened by the flat side surface of the

wheel along an involute helicoid, which is the enveloping surfacein the helical motion of the wheel.

Sharpening' Tools 'by GrindingHeli~al Sf!,rfaces

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Cracks, that may be formed in sharpening carbide tools are re­vealed by visual inspection with a magnifying glass or by fluorescent­penetrant inspection techniques ... ,·Thegeometry; dimensions and shape of a tool can be checked byvarious means-of .measurement. The simplest of these are templategauges of all kinds used to check geometrical parameters, as well asthe tool profile.

A' great many different types of tool angle protractors are inuse.They may be either of a type that .is to be applied to the tool or ofstationary construction. Figure 131a. illustrates how tool angles are­measured by a protractor designed in the USSR Tool ResearchInstitute. Its principle is based on the use of a weight which tends to­maintain the hand of the instrument in a vertical position, regard­less of the positionof the body of the protractor. 'I t can be employedto check the geometrical parameters of all kinds of cutting tools.A stationary, tool angle protractor for checking single-point toolsis shown..in .Fig. 131b. These protractors are very convenient in

.-operatlon hut -lessversatlle-then the applied type. . . ",Tool angles can also be checked by optical methods. Many types

of projectors and other optical instruments are used for this purpose,.some of which are based upon the Iight cross-section principle. '.~

Fig. 132. Measuring the rake angle with a vernier height gauge

. Gross defects, remaining after 'sharpening (worn areas, surfaceburns, etc.) are revealed by visual inspection. Surface finish is checkedby .comparison with surface-roughness .standards. Corupariscopes(special microscopes) are convenient for a quali tative evaluationof the surface finish on various types of cutting tools. 'Various profi­lometers and .profilographs can be employed to obtain a more accu­rate and objective evaluation.

........~ Lnspectton. of Sharpened Tools

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70 ' 90~~.,...,.-----~

stoel .. 8 ,~10'\ " ·90 ,Ovel:' ,~ 8' ' •_,___._-----,up ,to 80 8 - 10

A1Io,i' ,80 100 6 " ,8 ..- .."\ ... r J

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Quenched 8'ieel 5 up ~o - 20 -..

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r~'.Pure Copper la ;...15 e-Brass 10'- 15 6'

f---' e.Red-.alloy .I!> - 1~

Bz-onze lJ. - 12 3Zlna. alloya. e - 12 6M8.gne~li~ alloys 1~ - 2~ eP-are £1.11Ulllinl um I 20 - 30 10

1---- _.up to 50 15 - 20

Alluminl~m Alloys 50 - 100 12 - 15 aCasted 100 - 130 10 - 12

A.lhfmlnlum a110;-s 11-13[S;1. Over 130 6 - 10 a.Al1umj nl um ailoys-forged , - a

Hard rubber, plastics 10 - la 12.-'

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1~:Rocka 10 upt;-a ..- '.- .

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Bearins -10 upto 0 upto upto 8 - 10ltetala/ --

Cast iron -5 ul'to 0 60 4 Interna1 ~urh1d~

Steel -10 upto-5 10-15.___ .._---

a~el 1!ardnee a,0 yO )". itC° ~9HRJ . <f

~5 - 45 l! -10 -10 ~O,45 - 55 10 -15 ~20 20 1555 - .65 e -20 -40 10

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0 -5 0,2~220 as RougMng 6 upto 4.5-¬ O up 10 0 1- , - 10 -45

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r--_' ~-----------__t-------'~steel Over 100k,p/mmt

------------------------------~-------------+-----------at~el Ul' to 60 - 50 kp/lllm*Ca~t Iron 100--200 na

S'!:;eel u.p to 60 kp/mml

o ast Iron up tp 100 HE

-----------------,~~~---=--f-----------IAllumini~~ Alloys

(~~---~~----~------.------------------~--~--~--r-----------;l :, ': liIaterial to be Machined~~=r=-" m

Allumini-um And Copper

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-------------------+-~~--~---f__--~

0 - .510 - 15

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-_._-,30 - :40

12 - 18

L;2- 10

- 16, 6 - 10

~-------------·----------~~----~---------r.R~a~k~e--a-n-g~]~.e~p~l-.--a-ll-g~l~--~,L .M~teric-:.l to be m.achine,~ yO ij.o "'~'I_~t;a~_.::_ Stre;~th up to 50 lcp/E1!ll!i , 15 - 25 ',10

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:' 1

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2,' -1,0 i 3,0 ~t9 -" " -0:-

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~0.35 2,a 2,7 2,6 2,;0,50 3,1 3,0 2...t9 2t~

10 0,50 3,4 .3,2 3,1 '_

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~====-.---.-..,~.--------------------------------------------------------------

° c:.0 XMaterial to be machf.ned e;:

..

-kp/mm1Carbon Steel - up to 50 100 - 110....10 - 12

Carton a..o.d l.lloy Steel 110 1201! -50 - 90 kp/mill

Alloy Steel 90 - 110 kp/IJllll~125

Cast Steel

Alloy Steel Over 110 kp/mm~ .130 a - 10~L'3ten:!tie, St991I-- .

Cast Iron 90 - IJ5 25 + :2Malleable C ast- Iron",:, .Ferri tic :.;.:u,

14alleable. 0ast ..Iron...~.'··perlitic 100

Alluillinium Alloys 11 l~ .' 8i 140- 4...Heat Rcsista:at Steel

Stainless Steel .130 6 - 8

Hardened C:-.Ir;.t Iron

.Mang[-llje se Steel 12 I. NlD. 130 - J_'!;.\)Chromi'.lID Staal ,

·O.3.st :C""on Over 200 HB 120 ..

AI ;.uminium , Copper 140 12 - 1,5 45:

Allu.:;,l.n 1.urn Alleys - Formed 110 - 130 10_

12 30 7.c:; :, -MagEes~_um Alloys 110 120 15 20,,;, - - .

ll..ll::",mini ';10 -Alloys Casted 100 - 120 8 - 10 25 ._ ::0Zir..:.-s

,I .• A l.i.. cys 120 20'

Bz-oxiz e 100 - 120 12 - i s 10 20-: ./

Br-as s 120 12 - l~ "'C' .._.I c.J

Ha,r'i Rubber ·~O B - JJ).~.. P'l.as tLc e (50ft) . 100 - 120 6 B 10-PlastL~3 (Har) 80 - 1<2~ 6 - J]

~,.Har-de ne d Paper 130 10 - 12 15 .Marble 80 - 90 8 - 10 10·-:·15....

rt ___:~ ar~_~_~~

Brass, To'-I}:tght l~etr-Pl~Mti.~~D'---~.--.~..._._..~

Copper._.,..._...----------o-~-~

~ , :ICylindri- Disc .. oGutters'18.1 to be mactrLned -oaL cut-

! -tters nss S.C .._L______yo yO yO

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t-lP to GO 1.""]1/ 'ftrur? 12 - 20 12 5 - 10:lp to--080 k:p7mml: I: - 12 10 2 - 5up to lOOkp/mmi - a 8 00 ... 3- -- 0-P 4-' 120kp/Il!i~:.- 4- - 6: 6 .....5 up~o 0..,0

1, M~eable Gaet Iron ~ - 12. 10 2 - 05._ _

up to:150 HB 6 ~ 19 - 10 2 - 5OVBI' le30 liB' ~ 6 6 0 - r.::-- :;l-_ :

,12 - 20 20 15 - 26..--.,_- ......~ ..--------01 brittle brcnze i).._ - 5' 0_ :41- -5 uptrJ 0--ugh Br-nnz s e - 12 10 5 - 10_

o.1s 15 ~ 30 25 15 - 20_.o~____ ""'___ '_5 - 15 15 10 - 15

_,~.;ow . ,....... - -

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r--~Mat,e:z:

~_:_:_:_:---;

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0° ;>01

U.lI- to1° 30'

4~06.2.: Tool G.eometry For Hand Reamers

I?t

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t-.... -:---- J...llumini um and Allo;)r==~,Draaa .

L' Bronze t ~oP!:~:.__,_j___;.

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Chrome ~ ·Jrl.ck'e1.

120._...,...,.......,.._.......---.....-,,------.-.---.-~.-+--~.----+_.......;.-_4_.--~--_f8,5

70 - 85Steel ..60 -' '1050 - 60

r~"""I_____""-f . Mtj'ter5.a.l,'-=I

-·----~'~~-~T-Btrangthto be machined I kp/mm~

45 -'·50

l~~O:7e4J~ g Angles For Sawing D:tsca- ......- .....- .......---.---~..---_#_---_,.~

.\1Jing c~~~e~. ~!p~': Mi.lling method.. X'

". . '...,_~

10 20De Teethed Finishing -:- ,l'20',_ ,30'iwn Teethed Sesifiniahing.~- ' . '--"--._"g~.!_~~~ed· _ _l_3ough1ng~ 30 ~ 60

.. 2025 412 -

100 - 15C- " ;i

5·It- '15

7 - 15

"

10 - 15,

12 - 15

4.0742.: ~!£~r~DsQ_~D~1Q_f2~~L~ll!~G_Q~~~2E~_E~~~_~!B~_§E~~2_§!!££!_

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/58'

/

0Material '1'0 ~e "Machined o Roughing Finishingy

teeth teethSteel 50 kp/mml I 16 - 20 2 -·3Steel 50 - 70 kp/mm' 14 - 18Steel 70 - 90 kp/mml 10·- 12SteAl dYer 90 k.p/mmlCast Steel e - 10

Caa t Iron ..~.~~. 150 HB 1,5-2 0,5·- 1,

CQst Iron oyez' 150 liB 4 - 6MlQ1eable Ca~t Iron 7 - 10Bronze, Brass 3 - 10 1 -1,5

jLight Metals ..12 - 25 2 - ;;

Hearing Metals 10 - '15 0.0-1

400~. ~ Tool Angles For Broaching Tools-~---------------- - ~~--

..Matorial kp/mm' yO lF~c8t a.ose ·1)·elAachined Y ,f~;;eO .. ~o

HB p .,up to 60 -5 5 ·14 i

Steel up tc.100 -10 10 12 ..Over 100 -15 15- 10

Cast Steel -15 10 .7 GOInterupted c:~;tt- 10

-30 15 '10- .nll upto .5-

up to·180 +5 0 15 75Cast Iron up to 240 +3 5 10

Ov~r 240 0 10 6..Light Metals 18 - 0 14-----_ ..

4.07.5,:_~~51~~_E~~_M!!l!~5~e~d!-!!~h_§!~~~r~~_q~~!~~!i~~~

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115

Aluminium Alloy~18-25l ._._~·_-";-,----------------··-e_··-,-·--··--_+------_+------II.

13085

--------------.---.----..........-----~-...:;--~----~------_l1'+5

26:1

Drillil!lg

~"lI'r.r.

270

340

400f--.---

430

520

175

205

250

150

150

115 ._l::JO

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OetrbO.3. .st~f,jl 60 216l~.__,~,.----~A...~.-~.----~----~--.---.......J..-------+---.------+-----_.-l (1 rn.rbON Ht~Hll 70 245

21045

Millillg

,,365

450

495

505

540--250

[J.!:'p/m.!i12 ]

(Lt'-N]. ~1t~61, ------~-----------------+------------~I~--~'--:--

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160

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al'

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No LLt hI L5 h-2 g

0 - - ... -1 - - .... ...

1-42 ~ec .lPic*u iI:'e (I).

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06 29 35 75 47 15,9 :::a

80 29 43 82 54 19 H100 29 51 104 61 26 Q)

Pi120 29 59

fd104 68 32 H

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.. .p160 39 75 141 82 44 Ql

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'~

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