Intermediate and Advanced Machining

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Intermediate and AdvancedMachining

Adama Science and Technology University

Further Training Institute

Short Term TrainingAugust 2012


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Intermediate Lathe and Milling Operation

Introduction

eneral purpose lathe machines and milling machines are machine

tools !hich have !ide range o" operations#

Using theses machines it is possi$le to produce products !hich

re%uire "rom $asic to advanced machining s&ill o" the operator#

The "irst !ee& training is designed to give trainees some

intermediate training on $oth milling and lathe machine operations

This training is designed to "ill some $asic s&ill gaps and to asses

the trainees need so as to ma&e training more use"ul "or the trainees#

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'ontents o" the First (ee& Training

1# Sa"ety in the machine shop

2# Lathe operationsi# rinding single point cutting tool

ii# Speed) "eed and machining rate

iii# Setting up lathe machine

iv# *reparing !or& "or turning operation

v# Step turning on lathe machine

vi# Tapper turning

vii# *ro"ile turning

viii# Thread turning

i+# ,rilling operation

-# Milling operation

i# Speed) "eed and machining rate

ii# Inde+ing

iii# Simple gear calculationsiv# Setting up !or& holding device

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Lathe operationsrinding single point cutting tool

The most importantangles in grinding1. Side relief angle2. Bac relief angle

3. Bac rae angle!. Side rae angle5. "nd cutting edge

angle

6. side cutting edgean le

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Cutting Edge Angle

Side Cutting Edge and Lead Angles.

These angles are considered together $ecause the side cutting edge angle is

usually designed to provide the desired lead angle !hen the tool is $eing used#

End Cutting Edge Angle#

The sie o" the end cutting edge angle is important !hen tool !ear $ycratering occurs#

(hen cratering ta&es place) the recommended end cutting edge angle is to

1 degrees# I" there is no cratering) the angle can $e made larger#

Larger end cutting edge angles may $e re%uired to ena$le pro"ile turning tools

to plunge into the !or& !ithout inter"erence "rom the end cutting edge# Nose Radius#

The tool nose is a very critical part o" the cutting edge since it cuts the

"inished sur"ace on the !or&piece#



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Lathe operations



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EXAMPLE. $ 2%in%diameter metal rod has an

allowa&le cutting speed of 3'' sfpm for

a gi(en depth of cut and feed. $t whatre(olutions per minute )rpm* should themachine &e set to rotate the wor+

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Feed rate

-eed rate f, which is the movement of

the tool cutting edge in millimeters perrevolution of the )mm/re(*.

Depth of cut t,

which is measured in a directionperpendicular to the WP axis, for oneturning pass.

where d is the diameter of the machinedsurface



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EXA!LE.

(hat is the cutting time in minutes "or one passover a 104in length o" 2#24in4diameter rod !hen

the cutting speed allo!a$le is 20 s"pm !ith a "eed

o" 0#0- ipr5



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Volume of Metal Removed.

The volume of metal removed during a lathe

cutting operation can $e calculated as "ollo!s6

7+ample

ith a depth of cut of '.25 in and a

feed of '.125 in what (olume ofmaterial is remo(ed in 1 min whenthe cutting speed is 12' sfpm+

min8cmormin8inremovedmetalo"volume!here

unitsmetric"or

unitsinch"or12

--=

=

=

r

r

r

V

tfvV

tfvV



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Intermediate Milling OperationMilling is the removal of metal$yfeedingthe !or&

past a rotatingmulti toothed cutter#

The action o" the milling cutter is totally di""erent

"rom that o" a drill or a turning tool#

In turning and drilling) the tools are &ept continuously in contact

!ith the material to $e cut) !hereas milling is an intermittent

process) as each tooth produces a chip o" varia$le thic&ness#

Milling operations may $e classi"ied as

1. peripheral (plain) milling or

2. face (end) milling2/26/15 13Dagmawi Hailu


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!eripheral illing

the cutting occurs$y the teeth arranged ontheperipheryo" the milling cutter) and the

generatedsurfaceis a planeparallelto the

cutter ais#

*eripheral milling is usuallyperformedon

a hori!ontal milling machine#

For this reason) it is sometimes called

hori!ontal milling.



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$d(antages of up%millinginclude the followinga. 4t does not reuire a

&aclash eliminator.&. 4t is safer in operation )the

cutter does not clim& onthe wor*.

c. oads on teeth are acting

graduall.d. Built%up edge )B7"*

fragments are a&sent fromthe machined surface.

e. The milling cutter is not

a8ected & the sand orscal surfaces of the wor.

$d(antages of down%milling include thefollowing

a. -i9tures are simpler and lesscostl as cutting forces areacting downward.

&. -lat s or plates thatcannot &e :rml held can &emachined & down%milling.

c. ;utter with higher raeangles can &e used whichdecreases the powerreuirements.

d. Tool &lunting is less liel.

e. Down%milling is characteri


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illing Cutters

1. lain milling cutters )a*

2. -ace milling cutters )&*(ertical or inclined )d* =at surfaces.

3. Side milling cutters )e* orcutting a ewa )f*.

!. 4nterlocing )staggered*

side mills )g*5. Slitting saws )h*6. $ngle milling cutters )i*#. "nd mills )>* or (ertical

surfaces )*.

,. ?e%cutters )l and m*.0. -orm%milling cutters )o*1'.T%slot cutters)> and p*11.;ompound milling cutters

)*

12.4nserted tool millingcutters )*2/26/15 1,Dagmawi Hailu


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,ividing heads are attachments that e+tend the capa$ilities o" the milling

machines# They are mainly employed on &nee4type milling machines to enhance their

capa$ilities to!ard milling

straight and

helical "lutes)

slots)

grooves) and

gashes !hose "eatures are e%ually spaced a$out the circum"erence o" a

$lan& 9and less "re%uently une%ually spaced.#

Such /o$s include milling o" spur and helical gears)

spline sha"ts)

t!ist drills)

reamers)

milling cutters) and others#

The ,ividing :ead



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The ,ividing :ead

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Modes of Indexing



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7+amples6

It is re%uired to determine the suita$le inde+

plates and the num$er o" inde+ cran&revolutions n necessary for producing the

follo%ing spur gears of teeth num"er &' '

and * teeth.The plates ha(e the following num&er of

holes

Plate 1: 15, 1, 1!, 1", 1#, and $%

Plate $: $1, $&, $!, $#, &1, and &&

Plate &: &5, &!, , '1, '&, '!, and '#



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Hence the reuired turn of the wor spindle iso&tained as sum of two turns )-igure 3.61*

$ turn of the inde9 cran )2* relati(e to the inde9plate )1*$ turn of the inde9 plate itself which is dri(en

from the wor spindle through change gears )a()*

+ c(d* to provide the correction

Depending on the setup theinde9 plate rotates either inthe same direction with the

inde9 cran or in the oppositedirection. $n idler gear should&e used if the cran and platemo(e in opposite

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To per"orm a di""erential inde$ing% the "ollowing steps are to be considered&

The num$er o" revolutions o" inde+ cran& is set up in the same manner as in simple

inde+ing) $ut not "or the re%uired num$er o" divisionsZ. +nother num"erZ nearest to

Z ma,es it possi$le "or simple inde+ing to $e carried out#

The error o" such setupZis compensated for "y means of a respective setting up of the

di""erential change gears a " c and d

The change gears supplied to match the three plate system are 2;92.) 2) -2) ;0) ;;) ;)

=) =;) >2) =) and 100 teeth#

The num$er o" teeth o" the change gears a " c and d are determined from the

corresponding &inematic $alance e%uation6

Aote 4t is more con(enient to assume that-. / - to avoid the use of

an idler gear0 f -. 2 -, then an idler gear must &e used2/26/15 26Dagmawi Hailu


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E$ample '

Select the di""erential change gears and theinde+ plate) and determine the num$er o"

revolutions o" the inde+ cran& "or cutting a

spur o"Z = 227 teeth.

BCD22'

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'utting ?evel ears


The hypotenuse o" the triangle is t!ice the pitch cone radius#

Thepitch diameter 9gear and pinion.) the number of teeth 9gearand pinion.) and the actual ratio$et!een the gear and the pinion

are all in ratio#There"ore) !e can use any o" these three sets to "ind the pitch

cone angle 9*'A.#


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*arts o" a $evel gear

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$ddendum angle


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SELECT#N( A )E*EL (EAR C+TTER

To cut $evel gears on the milling machine) you must use

specialform relieved cutters.

These cutters are similar in appearance and sie to those

used to cut spur gears) $ut they have thinnerteeth# They are made to cut gears !ith a "ace !idth not greater

than onethirdnor lessthan oneeightho" the distance

"rom the bac!o" the gear to the ape"o" the cone#

The contour o" the cutter teeth is made "or the large endof the gear.

The tooth shape at any other section) then) is only an

appro"imationo" the current "orm "or that section#



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SELECT#N( A )E*EL (EAR C+TTER

Suppose you plan to cut a $evel gear !ith -0 teeth and a ;C pitch cone

angle#

Using the @T'S "ormula) you !ill "ind the imaginary spur gear to have ;-

teeth#

There"ore) $y using a standard chart) you can determine the proper cutter

"or this gear to $e a @o# - cutter !ith a = diametral pitch#



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MILLI@ T:7 ?7D7L 7A3 T77T:

Milling $evel gear teeth involves three distinctoperations#

First) gash the teeth into the gear $lan&)

then mill each side o" the teeth to the correct tooth thic&ness#

In the "irst operation) mount the selected cutter on the milling

machine ar$or and center the $lan& on the cutter#

Then $ring the milling machine ta$le up to cut the !hole depth you

determined "or the large end o" the gear#

A"ter you cut the "irst tooth) inde+ the gear $lan& in the same manner as you

!ould to cut a spur gear) and gash the remaining teeth#

In the second and third operations) mill the sides o" the teeth that

!ere "ormed in the gashing operation#



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To accomplish the roll) you must &no! the amount o"

inde+ cran& movement) !hich you can "ind !ith the

"ollo!ing "ormula6


A"ter you have milled the $evel gear teeth completely) measure the tooth thic&ness o" the

pitch line o" $oth the large and the small ends o" the gear#


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:elical ear 'utting

A heli+ is a line that spirals around a cylindricalo$/ect) li&e a stripe that spirals around a $ar$er

pole#

A helical gear is a gear !hose teeth spiral around

the gear $ody#

:elical gears transmit motion "rom one sha"t to

another#

The sha"ts can $e either parallel or set at an angle

to each other) as long as their a+es do not intersect

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'hordal Thic&ness and 'hordal Addendum

Before St

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'omputer @umerical 'ontrol *rogramming

$umerical control %$C&

is a "orm o"programma"leautomation in !hich the mechanical actions o" a machine toolor other e%uipment are controlled$y aprogramcontaining coded alphanumeric data#

The alphanumericaldata represent relative positions#

@umerical control can $e applied to a !ide variety o" processes#

The applications divide into t!o categories

Documents

Intermediate and Advanced Machining