Machining [Compatibility Mode]

Machining

What is it? Machining: A subtractive

process used to get desired What is it?p ocess used to get des edshape, size, and finish byremoving surplus material inthe form of chips by a cuttingtool and by providing suitablerelative motion between therelative motion between theworkpiece and cutting tool

Cutting tool: removes excessgmaterial through directmechanical contact

Machine tool: providesnecessary relative motionbetween the work piece andbetween the work-piece andtool

Basics of shape generation by machiningT l ti ti (b t k d t l) Two relative motions (between work and tool)generally needed to produce surfaces Cutting speed: line generated by it is calledCutting speed: line generated by it is called

generatrix: Primary cutting motion Feed speed: line generated by it is called

di i S d i idirectrix: Secondary cutting motion

Relative motions needed for i f ivarious types surface generation

Surface Obt i d

Machini Generatrix( tti )

Directrix(f d)Obtained ng

Process (cutting) (feed)

Planar Shapin Straight StraightPlanarSurface

Shaping,Planing

StraightLine

StraightLine

Cylindrica Turning Circular StraightCylindrical

Turning Circular StraightLine

Planar Milling Circular StraightSurface LineSurface ofRevolutio

ContourTurning

PlainCurve

Circular

ng

,Boring

TYPES OF MACHINING PROCESSESBASED ON ANGLE BETWEEN CUTTING

EDGE d CUTTING VELOCITYEDGE and CUTTING VELOCITYOblique Machining Orthogonal Machining

Cutting edge of the tool Cutting edge of the tool is Cutting edge of the toolis inclined with normalto the cutting velocity.

Cutting edge of the tool isperpendicular to thedirection of cutting velocity

C tti F A t C tti F A t Al Cutting Forces Actalong All ThreeDirections i.e. x, y, and zAxes

Cutting Forces Act Along xand z Directions Only i.e.No Cutting Force along yDirectionAxes. Direction

Examples:Turning,

Examples:Sawing,

Milling,Drilling,Shaping

Broaching,Parting-Off of Tube Wall

Shaping

MI-102: Manufacturing Techniques I. I. T. ROORKEE

Machining Processes

ACCORDING to TYPE of CUTTING TOOL

Using SINGLE-Point Cutting Tools

Using MULTI-Point Cutting Tools

Using ABRASIVES as Cutting Tools

g

g g

Turning Step Turning

Milling Drilling

Grinding Honing Step Turning

Taper Turning Form Turning Contour Turing

Drilling Reaming Knurling Tapping

Honing Lapping Super-Finishing Polishingg Facing

Necking Parting-Off Boring

pp g Hobbing Broaching Sawing

Polishing Buffing

Boring Counter-

Boring Counter-

Sinking Shaping Planing

LATHE MACHINE and its OPERATIONSh h l d i il Lathes are Machine Tools Designed Primarily to Do

Turning, Facing, and Boring. Because Lathes also can Do Facing, Drilling, and

Reaming, their Versatility Permits Several Operations

S G d O OG f h GDESIGN and TERMINOLOGY of the ENGINE LATHEThe Essential Components of an Engine Lathe are

1. Bed2. Headstock Assembly3. Tailstock Assembly4. Carriage Assembly

5. Feed Rod6. Leadscrew7. Quick Change GearboxQ g


Tailstock

Bed


BedSchematic Diagram of an Engine Lathe

Carriageassemblyasse b y

Carriageassemblyprovides theprovides themeans formounting andmoving cuttingmoving cuttingtools.

Carriageblassembly

consists ofcarriage, crossslide,compound rest,tool post


p

Feed rod provides provides

thepoweredmovemenmovement of thecarriageand crossslide forautomaticautomaticmovementof toolused in

Leadscrew for cutting threads, a leadscrew is

used to provide automatic

used inturningoperation

used to provide automaticmovement to carriage.

SIZE DESIGNATION of LATHES Size of a Lathe is Designated by Two Dimensions:g y

1. Swing diameter: shows maximum diameter of work-piece that can be rotated on a lathe.

i i d h2. Maximum Distance Between Centers: Indicates theMaximum Length of Workpiece that can be MountedBetween Centers.

Example: A 14 x 48 Lathe designates thatdesignates that the swing is 14 in. and the maximummaximum distance between centers is 48 inis 48 in.

Type of l th

Engine lathe, Speed lathe,

T l l th lathes Tool room lathe, Turret lathe, Automatic lathe, Numerical control lathe

ENGINE LATHE Most frequently used in

manufacturing They are heavy duty

machine tools with all thet hcomponents have power

drive for all toolmovements except onmovements except oncompound rest.

Most engine lathes are Most engine lathes areequipped with chip pansand a built-in coolantand a built-in coolantcirculating system.

SPEED LATHES d l th llSpeed lathes usually

have only aheadstock aheadstock, atailstock, and asimple tool postp p

Usually three or fourspeeds

Mainly used forwood turning,polishing or metalpolishing, or metalspinning

Spindle speeds up to


Spindle speeds up to4000 rpm.

Tool room lathe Greater accuracy and

usually a wider rangeof speeds and feedsthan engine lathes.

Designed to havegreater versatility tomeet the requirementsof tool and die work

Generally used formachining smallerparts

Turret latheH T t R l Hexagon Turret Replacesthe Tailstock

Turret used for mountingtools and feed into the workpiece

Turret Lathes Use the 11 RAM TYPEu et at es Use t eStation Tooling and so asto increase productionrate by reducing toolrate by reducing toolchanging time .

SIX Tools can be Mountedon the Hexagon Turreton the Hexagon Turret

Turret can be Rotatedabout the Vertical Axis toB i E h T l i t thBring Each Tool into theOperating Position

Ram and saddle l h

SADDLE TYPEtype turret lathe

Primary difference is

TYPE

yin mounting and sizeof two types.

Ram type is light,less rigidity and sog yfor small jobs usingfine cuts

RAM TYPE

Saddle type heavy,more rigid, largeg , gjobs and heavy cuts

Operation of lathe

Turning is the process of Machining external cylindrical and conical surfaces. cy d ca a d co ca su aces Straight turning: for producing cylindrical shapes Taper turning: for producing conical shapes p g p g p Facing: making edges square and clear Chamfering: slightly tapering and rounding off of g g y p g g

edges Threading: for producing threads Drilling: for creating /producing hole Boring: for enlarging hope and correcting shape Parting off or necking: separating or making square

groove K li ki i i f fi i i Knurling: making impression for firm gripping

Reaming: finishing purpose

Straight/cylindrical turningStraight/cylindrical turning

Orthogonal turning Oblique turning g g q g

TAPER TURNING

Cutting tool is fed at an angle to the axisof rotation producing anexternal/internal conical surface.

Tapers generally specified in degrees ofi l d d l b t th id ( tincluded angle between the sides (or rateof change in diameter along the lengthmm/mm)

FOUR Methods for Taper turning: Swiveling the Compound Rest: Only for

Short and steep Tapers Taper turning attachment: for fine taper-ness

less than 0 5mm/mmless than 0.5mm/mm Setting over tailstock: low taper in long jobs NC lathe with programmed both movements of


movement of tool

Swiveling the compound rest Tool is set

at half of taper angle w.r.t. lathew.r.t. lathe axis and moved with compoundcompound rest only

Taper turning attachment

Crossslide ismade freemade freeand toolis movedwith helpwith helpofattachmet tnt at an

angle

Off setting the tail stock

Tool is moved with help pof carriage parallel to the lathe axis

Contour turning

The tool follows a contourcreating a contoured form onthe turned part instead ofthe turned part instead ofparallel to the axis. Cross slideis made free to follow the pathof contour.

FORM TURNINGFORM TURNING

Cutting edge of Tool has a SpecificF Sh d i f d di llForm or Shape and is fed radiallyinward towards the axis of rotatingwork piece.

FACING

Cutting tool is fed radially inwards(at 90 w.r.t. the axis of rotation) into( )the rotating work piece.

End facing: facing by tool movingradially outward from the center

Shoulder facing: facing the steppedcylindrical work piececylindrical work piece

Chamfering The tool is fed radially inward

used to cut an angle on thecorner of the cylindercorner of the cylinder,forming a chamfer to avoidsharp edges.

Parting off & necking

Tool is fed perpendicular tothe rotational axisthe rotational axis

Necking is a making partialcutoff


DRILLING The tool (Drill) mounted on the

tailstock of the engine lathesis fed by hand against arotating work piece along theaxis of lathe.

BORING

Tool mounted to tailstock isfed parallel to the lathe axispafter giving suitable depth ofcut


REAMING It is semi-finishing

operation that enlargesoperation that enlargesan existing hole. Tool isrotated and fed along

t ti l irotational axis.knurling Roughening the surface of work Roughening the surface of work

piece for better gripping. No machining operation only cold-

Process involves pressing of

g p yforming takes place

two hardened rolls against therotating work piece with sufficientforce to form impression (the knurl)like raised diamond pattern.

Work holdingdevices

Face plate: for holding irregular devices shape w/p

Lathe centers: for holding long jobs

Chuck: 3 jaw chuck for circular or

hexagonal section g 4 jaw chuck for irregular

shapes p Magnetic chuck for holding

soft metalsoft metal

MandrelMandrel: forholding hollow discMandrel gshape w/p formachining of sidefacesfaces

Collet: for holingll di t t lsmall diameter tool

and work pieces

Collet

CUTTING TOOLS USED In a LATHE Single Point Cutting Tools

common cutting tool materials

Single Point Cutting Tools Bit-Type Cutting Tools Form Tools (tapering and Threading Tool)common cutting tool materials For conventional machining processes, cutting

tool material must be at least 35% to 50%h d th k t i l t th t lharder than work material at the actualtemperature of machining

1. tool steels2. high speed steel (hss)3. cemented carbides4. coated carbides5 i5. ceramics6. cermets (ceramic material in a metallic binder)7. sintered polycrystalline cubic boron nitride

(cbn)


(cbn)8. sintered polycrystalline diamond (pcd)

Geometry of single pointsingle point cutting tool

FUNDAMENTALS of DRILLING OPERATIONS

Drilling is a machining operation of creating a hole in awork-piece which can be through holes or blind holes,performed with a rotating cylindrical tool having TWOperformed with a rotating cylindrical tool having TWOcutting edges called a twist drill.

Rotating drill is fed into the stationary work piece to Rotating drill is fed into the stationary work-piece toform a hole whose diameter is determined by the drilldiameter.


OPERATIONS RELATED to DRILLING

REAMING: A Semi-Finishing Operation to Slightly Enlarge an Existing Hole To Provide Better Tolerance on Hole Diameter To Improve Surface Finish

TAPPING: To Make INTERNALThreads on an Existing Hole UsingTapsTaps


COUNTER-BORING:

M ki f INTERNAL STEPPED HOLE i Making of INTERNAL STEPPED HOLE inwhich a Lager Diameter Follows aSmaller Diameter Partially into theHole

COUNTER-SINKING:

Similar to Counter-Boring, Exceptthat the Step in the Hole is ConeShaped for Flat-Head Screws andpBolts.

CENTERING or CENTER-DRILLING:

Drilling of a Starting Hole toAccurately Establish its Location forSubsequent Drilling.q g

TYPICAL SEQUENCE ofOPERATIONS in aOPERATIONS in aHOLE MAKING


CUTTING TOOLS USED in DRILLING

A Twist Drill has THREE Basic Parts: Body, Point, andShank

A Twist Drill has TWO Helical Grooves Called FlutesSeparated by Lands.

Flutes Act as Passageways for Extraction of Chips Fromthe Holethe Hole

Point of the Twist Drill has the General Shape of a Conehaving a Typical Value of 1180.


Geometry of Twist Drill.

DRILLING MACHINE Drilling is Most Commonly Performed on a Drill Press.DRILL PRESS C i tDRILL PRESS Consists

of Following Parts1. Base, 1. Base, 2. Column 3. Power-Head 4. Spindle 5. WorktableThese may be bench These may be bench

or floor mounted depending on the size

Drill can be fedmanually or


Upright Drill Press.manually orautomatically

TYPES of DRILLING MACHINES

MAIN ApplicationsTYPE

1. BENCH Holes up to 0.5 in. Diameterb D ill d V Hi hcan be Drilled. Very High

Speed up to 30,000 rpm2. Speeds Ranges from 60 to2. UPRIGHT

Speeds Ranges from 60 to3500 RPM

3. For Large Workpieces thatRADIAL Cannot Easily be Handled

Manually.4 GANG Mass Production variety of4. GANG Mass Production variety of

purposes such as Holes ofDifferent Sizes, Reaming,Counterboring, on a SinglePart.

TYPES of DRILLING MACHINES

MAIN Applications DesignationMAIN TYPE

Applications, Designation

5. MULTI- Mass Production Machines with as manySPINDLE

yas 50 Spindles Driven by a SinglePower head and Fed Simultaneouslyinto Workinto Work.

6. DEEP-HOLE

For Drilling Long (Deep) Holes inRifle Barrels, Connecting Rods, andLong Spindles.

BENCH TYPEUPRIGHT DRILLING MACHINE

Milling Milling is a machining operation in which a work- Milling is a machining operation in which a work-

part is fed past a rotating cylindrical tool calledmilling cutter is multi point cutting tool.

In milling axis of rotation of the cutting tool is In milling axis of rotation of the cutting tool isperpendicular to the direction of feed.

While in drilling, the cutting tool is fed in adi ti ll l t it i f t tidirection parallel to its axis of rotation.

HORIZONTAL TYPE VERTICAL TYPE

Geometric form created by milling is a planef d th t i d i h bsurface and other geometries are created either by

controlled cutter path or the cutter shape.

f f Typical feature of milling: it is an interrupted cutting operation the teeth of the milling cutter enter and exit the

work during each revolution.

so cycle of impact force and thermal shock inevery rotation.

the tool material and cutter geometry must bedesigned to withstand these conditions.

TYPES of MILLING OPERATIONSPERIPHERAL MILLING FACE MILLING

i f t l i ll l t th i f t l i di l t thaxis of tool is parallel to thesurface being machined

axis of tool is perpendicular to thesurface being machined

machining is performed by cuttingedges on the outside periphery

machining is performed by cuttingedges on both the end andg p p y

of the cutter.g

outside periphery of the cutter.

TYPES of PERIPHERAL orPLAIN MILLING

TYPES of FACE MILLING

(a) slab milling: basic form of (a) conventional face milling:(a) slab milling: basic form ofperipheral milling in which the cutterwidth extends beyond the work-piece on both sides.

(a) conventional face milling:the diameter of the cutter isgreater than the work-partwidth, so that the cutteroverhangs the work on bothoverhangs the work on bothsides.

(b) slot milling (slotting): thewidth of the cutter is less than thework-piece width. very thin cutter

(b) partial face milling: thecutter overhangs the work ononly one side.p y

can be used to mill narrow slots or tocut a work-part in two, called sawmilling.

y

TYPES of PERIPHERAL MILLING TYPES of FACE MILLING

(c) side milling: cutter machinesthe side of the workpiece

(c) end milling: the cutterdiameter is less than the workthe side of the workpiece. diameter is less than the workwidth, so a slot is cut into thepart.

(d) straddle milling: the same asside milling, only cutting takes

(d) profile milling: this is a formof end milling in which the outside

place on both sides of the work. periphery of a flat part is cut.


TYPES of PERIPHERAL TYPES of FACE MILLINGaccording to the rotationdirection of the cutter two types:( ) ti l th

(e) pocket milling: another formof end milling, this is used to mill

f(e) up or conventional: thedirection of motion of the cutteris opposite to the feed direction.

shallow pockets into flat parts.

(f) down or climb milling: thedi ti f tt ti i i

(f) surface contouring: a ball-tt i f d b k d f thdirection of cutter motion is in

the feed directionnose cutter is fed back and forthacross the work along a curvilinearpath at close intervals to create a3-dimensional surface form.


DIFFERENCES UP Milling DOWN Milling

The direction of motion ofth tt i it t th

The direction of cutterti i i th f dthe cutter is opposite to the

feed direction.motion is in the feeddirection

It is milling against the It is milling with the feed."g gfeed."

g

Cutting force direction istangential to the periphery of

Cutting force direction isdownward tending to holdtangential to the periphery of

the cutter which tends to liftthe work piece as the cutterexits the material

downward, tending to holdthe work against themilling machine table.

exits the material.


Type Applications

TYPES of MILLING MACHINES

(a) column and knee type

( )

for slab, side, or straddle milling. well suited for face and end

(general purpose) milling operations for milling to produce twistdrills), milling cutters, and helicalgear teeth, etc.

(b) bed t pe for making hea c ts(b) bed type (manufacturing)

for making heavy cuts simultaneous milling of two orthree surfaces in a single passg p

(c) planer milling machines

for machining a wide variety ofsurfaces on heavy workpiece in a


single setup.

Milling cutter Milli tt l ifi d th b i f Milling cutters are classified on the basis of

methods of mounting and direction of rotation. Method of mounting

arbor cutters have a center hole for mounting onan arbor.

shank cutters have either a tapered or a straightshank.tapered shanks cutters can be mounteddirectly in the milling machine spindle.straight shank cutters are held in a chuck.


BASED ON DIRECTION OF ROTATION (Applies only toFace and End Milling Cutters)

A right-hand cutter must rotate counterclockwisewhen viewed from the front end of the machinespindle.p

A left-hand cutter must rotate clockwise.

Arbor for a Horizontal Spindle Milling

Typical geometry of milling cutterTypical geometry of milling cutter

Documents

Machining [Compatibility Mode]