Workshop manual for fitting,welding and machine shop

7/29/2019 Workshop manual for fitting,welding and machine shop

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Indian Institute of Technology Hyderabad

ME 101: WORKSHOP PRACTICE I

Pushing frontiers


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April 2009PREFACE

Theengineerscancreateanewkindofcivilization,basedontechnology,whereart,beautyand

finerthingsoflifeareacceptedaseveryonesdue.Engineers,whateverbetheirlineofactivity,mustbe

proficientwithallaspectsofmanufacturing.However, itshouldnotbeforgottenthatpracticewithout

theory isblindand the theorywithoutpractice is lame.Aperson involved inacquiringmanufacturing

skillsmusthavebalancedknowledgeoftheoryaswellaspractice.Thisbook iswrittentomeet theobjectivesof thetrainingcourses inworkshoppracticeforall

the first year engineering courses in Indian institute of technology Hyderabad. It imparts basic

knowledgeofvarioustoolsandtheiruseindifferentsectionsofmanufacturesuchasfitting,carpentry,

welding,machineshopetc.

Thestudyofworkshoppracticeactsas thebasis for further technicalstudies.Thisbookgives

theperceptiontobuildtechnicalknowledgebyactingasaguideforimpartingfundamentalknowledge.

Numerousneatlydrawn illustrationsprovided in the textwillhelp the students inunderstanding the

subject,andtheconceptsrelatedit,better.

Sincereattemptshavebeenmadetopresentthecontentsinasimplelanguage,supplemented

withlinediagrams,whichareselfexplanatoryandeasytoreproduce.

Wewould like toexpressoursincere thanks toprofessorsandcolleagues for theirconsistent

support.Suggestionsforimprovementinthisbookwillbethankfullyacknowledgedandincorporatedinthenextedition.

K.SathyanarayanaN.A.Somasundaram

P.Raju

25April2009


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Contents

PrefaceTableofContents page1.FittingShop

1.1

Introduction

1.2 Holdingtools

1.3 Markingandmeasuringtools

1.4 Cuttingtools

1.5 Finishingtools

1.6 Miscellaneoustools

1.7 Safepractice

1.8 Modelsforpreparation

Exercises

1

1

2

5

8

10

11

12

13

2.Carpentry

2.1 Introduction

2.2 Timber

2.3

Markingand

measuring

tools

2.4 Holdingtools

2.5 Planingtools

2.6 Cuttingtools

2.7 Drillingandboringtools

2.8 Miscellaneoustools

2.9 Woodjoints

2.10 Safe practice

Exercises

15

15

16

17

18

28

20

21

22

24

25

3.Welding

3.1 Introduction

3.2 Arcwelding

3.3 Weldingtools

3.4 Techniquesofwelding

3.5 Typesofjoints

3.6 Weldingpositions

3.7 Advantages&disadvantagesofarcwelding

3.8 Safepractice

Exercises

28

28

30

31

32

33

33

34

35

4.MachineShop

4.1 Introduction

4.2 Lathe

4.3 Workholdingdevices

4.4 Measuringtools

4.5 Cuttingparameters

4.6 Toolmaterials

4.7 Toolgeometry

4.8 Latheoperations

4.9 Safetyprecautions

39

39

40

40

41

41

42

42

44

Exercises 45

References 48


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Chapter1

FITTINGSHOP

1.1INTRODUCTION

Machine toolsare capableofproducingworkata faster rate,but, thereareoccasionswhen

components are processed at the bench. Sometimes, it becomes necessary to replace or repair

componentwhichmustbefitaccuratelywithanothercomponentonreassembly.Thisinvolvesacertainamountofhand fitting.The assemblyofmachine tools,jigs,gauges,etc, involves certainamountof

benchwork.Theaccuracyofworkdonedependsupontheexperienceandskillofthefitter.

Thetermbenchworkreferstotheproductionofcomponentsbyhandonthebench,whereas

fittingdealswhichtheassemblyofmatingparts,throughremovalofmetal,toobtaintherequiredfit.

Both the bench work and fitting requires the use of number of simple hand tools and

considerablemanual efforts. The operations in the aboveworks consist of filing, chipping, scraping,

sawingdrilling,andtapping.

1.2HOLDINGTOOLS

1.2.1Benchvice

Thebenchviceisaworkholdingdevice.Itisthemostcommonlyusedviceinafittingshop.The

benchviceisshowninFigure1.1.

Figure1.1:BenchVice

Itisfixedtothebenchwithboltsandnuts.Thevicebodyconsistsoftwomainparts,fixedjaw

andmovablejaw.When thevicehandle is turned inaclockwisedirection, the slidingjaw forces the

workagainstthefixedjaw.Jawplatesaremadeofhardenedsteel.Serrationsonthejawsensureagood

grip.Jawcapsmadeofsoftmaterialareusedtoprotectfinishedsurfaces,grippedinthevice.Thesizeof

theviceisspecifiedbythelengthofthejaws.

The vice body ismade of cast Ironwhich is strong in compression,weak in tension and so

fracturesundershocksandthereforeshouldneverbehammered.

1.2.2Vblock

Vblock isrectangularorsquareblockwithaVgrooveononeorbothsidesopposite toeach

other.TheangleoftheVisusually900.Vblockwithaclampisusedtoholdcylindricalworksecurely,

during layout of measurement, for measuring operations or for drilling for this the bar is faced

longitudinally in theVGrooveand thescrewofVclamp is tightened.Thisgrip therod is firmwith its

axisparalleltotheaxisofthevgroove.

1.2.3CClamp

Thisisusedtoholdworkagainstanangleplateorvblockoranyothersurface,whengrippingis

required.


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ItsfixedjawisshapedlikeEnglishalphabetCandthemovablejawisroundinshapeanddirectly

fittedtothethreadedscrewattheend.Theworkingprincipleofthisclamp isthesameasthatofthe

benchvice.

Figure1.2:Vblock Figure1.3:Cclamp

1.3

MARKING

AND

MEASURING

TOOLS

1.3.1Surfaceplate

The surfaceplate ismachined to fine limitsand isused for testing the flatnessof thework

piece.Itisalsousedformarkingoutsmallboxandismorepreciousthanthemarkingtable.Thedegree

ofthefinisheddependsuponwhetherit isdesignedforbenchwork inafittingshoporforusing inan

inspectionroom;thesurfaceplateismadeofCastIron,hardenedSteelorGranitestone.Itisspecified

bylength,width,heightandgrade.Handlesareprovidedontwooppositesides,tocarryitwhileshifting

fromoneplacetoanother.

Figure1.4:Surfaceplate Figure1.5:Angleplate

1.3.2Trysquare

Itismeasuringandmarkingtoolfor900angle.Inpractice,itisusedforcheckingthesquarenessofmany typesofsmallworkswhenextremeaccuracy isnot required .Thebladeof theTry square is

madeofhardenedsteelandthestockofcastIronorsteel.ThesizeoftheTrysquareisspecifiedbythe

lengthoftheblade.

1.3.3Scriber

AScriberisaslendersteeltool,usedtoscribeormarklinesonmetalworkpieces.Itismadeof

hardenedandtemperedHighCarbonSteel.TheTipofthescriberisgenerallygroundat12oto15o.

Itisgenerallyavailableinlengths,rangingfrom125mmto250mm.Ithastwopointedendsthebentend

isusedformarkinglineswherethestraightendcannotreach.


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Figure1.6:Trysquare Figure1.7:Scriber

1.3.4OddlegCaliper

ThisisalsocalledJennyCaliperorHermaphrodite.Thisisusedformarkingparallellinersfrom

afinishededgeandalsoforlocatingthecenterofroundbars; ithasone legpointed likeadividerand

theother

leg

bent

like

acaliper.

Itisspecified

by

the

length

of

the

leg

up

to

the

hinge

point.

1.3.5Divider

It isbasically similar to the calipersexcept that its legs are kept straight andpointed at the

measuringedge.Thisisusedformarkingcircles,arcslayingoutperpendicularlines,bysettinglines.Itis

madeofcasehardenedmildsteelorhardenedand tempered lowcarbonsteel. Itssize isspecifiedby

thelengthoftheleg.

Figure1.8:Oddlegcaliperanddivider

1.3.6Trammel

Trammelisusedfordrawinglargecirclesorarcs.

1.3.7Punches

Theseareusedformakingindentationsonthescribedlines,tomakethemvisibleclearly.Thesearemadeofhighcarbonsteel.Apunchisspecifiedbyitslengthanddiameter(sayas15012.5mm).It

consistsofacylindricalknurledbody,whichisplainforsomelengthatthetopofit.Attheotherend,it

isgroundtoapoint.Thetaperedpointofthepunchishardenedoveralengthof20to30mm.

Dotpunch is used to lightly indent along the layout lines, to locate center of holes and toprovidea smallcentermark fordividerpoint,etc. for thispurpose, thepunch isground toaconical

pointhaving60includedangle.

Centerpunch issimilartothedotpunch,exceptthat it isgroundtoaconicalpointhaving90includedangle.Itisusedtomarkthelocationoftheholestobedrilled.


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Figure1.9:Punches

1.3.8Calipers

Theyareindirectmeasuringtoolsusedtomeasureortransferlineardimensions.Theseareused

with the help of a steel Rule to check inside and outsidemeasurements. These aremade of Case

hardenedmildsteelorhardenedandtemperedlowcarbonsteel.Whileusing,butthelegsofthecaliper

aresetagainstthesurfaceofthework,whetherinsideoroutsideandthedistancebetweenthelegsis

measuredwiththehelpofascaleandthesamecanbetransferredtoanotherdesiredplace.Theseare

specifiedbythelengthoftheleg.Inthecaseofoutsidecaliper,thelegsarebentinwardsandinthecase

ofinsidecaliper,thelegsbentoutwards.

Figure1.10:Calipers

1.3.9VernierCalipers

Theseareused formeasuringoutsideaswellas insidedimensionsaccurately. Itmayalsobe

usedasadepthgauge.Ithastwojaws.Onejawisformedatoneendofitsmainscaleandtheotherjaw

ismadepartofavernierscale.

Figure1.11:Verniercaliper


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1.3.10VernierHeightGauge

TheVernierHeightgaugeclampedwithascriber.ItisusedforLayoutworkandoffsetscriberis

usedwhen it isrequired to takemeasurement from thesurface,onwhich thegauge isstanding.The

accuracyandworkingprincipleof thisgaugeare the sameas thoseof theverniercalipers. Its size is

specifiedbythemaximumheightthatcanbemeasuredbyit.ItismadeofNickelChromiumSteel.

Figure1.12:VernierHeightgauge

1.4CUTTINGTOOLS

1.4.1HackSaw

TheHackSawisusedforcuttingmetalbyhand.Itconsistsofaframe,whichholdsathinblade,

firmly inposition.Hacksawblade isspecifiedby thenumberof teeth forcentimeter.Hacksawblades

haveanumberofteethrangingfrom5to15percentimeter(cm).Bladeshavinglessernumberofteeth

percmareusedforcuttingsoftmaterialslikealuminum,brassandbronze.Bladeshavinglargernumber

ofteethpercentimeterareusedforcuttinghardmaterialslikesteelandcastIron.

Hacksawbladesareclassifiedas(i)Allhardand(ii)flexibletype.Theallhardbladesaremadeof

H.S.S,hardenedand tempered throughout to retain theircuttingedges longer.Theseareused tocut

hardmetals.Thesebladesarehardandbrittleandcanbreakeasilybytwistingandforcingthemintothe

workwhilesawing.FlexiblebladesaremadeofH.S.Sorlowalloysteelbutonlytheteetharehardened

and the restof theblade is softand flexible. Theseare suitable forusebyunskilledor semiskilled

persons.

Figure1.13:Hacksawframewithblade

Theteethofthehacksawbladearestaggered,asshowninfigureandknownasasetofteeth.

Thesemakeslotswiderthanthebladethickness,preventingthebladefromjamming.


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Figure1.14:Setofteeth

1.4.2Chisels

Chiselsareused for removing surplusmetalor for cutting thin sheets.These toolsaremade

from0.9%to1.0%carbonsteelofoctagonalorhexagonalsection.Chiselsareannealed,hardenedand

temperedtoproduceatoughshankandhardcuttingedge.Annealingrelievestheinternalstressesina

metal.Thecuttingangleofthechiselforgeneralpurposeisabout60.

Figure1.15:Flatchisel

1.4.3TwistDrill

Twistdrillsareused formakingholes.ThesearemadeofHighspeed steel.Bothstraightand

tapershanktwistdrillsareused.Theparallelshanktwistdrillcanbeheldinanordinaryselfcentering

drillcheck.The tappershank twistdrill fits intoacorresponding taperedboreprovided in thedrilling

machinespindle.

Figure1.16:Twistdrills

1.4.4TapsandTapwrenches

Atapisahardenedandsteeltool,usedforcuttinginternalthreadinadrillhole.HandTapsare

usually supplied in setsof three ineachdiameterand thread size.Each setconsistsofa tapper tap,

intermediatetapandplugorbottomingtap.Tapsaremadeofhighcarbonsteelorhighspeedsteel.


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Figure1.17:Tapsandtapwrench

1.4.5Diesanddieholders

Diesare thecutting toolsused formakingexternal thread.Diesaremadeeithersolidorsplit

type.Theyarefixedinadiestockforholdingandadjustingthediegap.TheyaremadeofSteelorHigh

CarbonSteel.

Figure1.18:Diesanddieholder

1.4.6

Bench

Drilling

Machine

Holesaredrilled for fasteningpartswithrivets,boltsor forproducing internal thread.Bench

drillingmachineisthemostversatilemachineusedinafittingshopforthepurpose.Twistdrills,madeof

toolsteelorhighspeedsteelareusedwiththedrillingmachinefordrillingholes.

Followingarethestagesindrillingwork

1. Selectthecorrectsizedrills,putitintothecheckandlockitfirmly

2. Adjustthespeedofthemachinetosuittheworkbychangingthebeltonthepulleys.Usehighspeed

forsmalldrillsandsoftmaterialsandlowspeedforlargediameterdrillsandhardmaterials.

3. Layoutofthelocationofthepoleandmarkitwithacenterpunch.

4. Holdtheworkfirmlyintheviceonthemachinetableandclampitdirectlyontothemachinetable.

5. Putonthepower,locatethepunchmarkandapplyslightpressurewiththeFeedHandle.


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6. OnceDrilling is commencedat the correct location,applyenoughpressureand continuedrilling.

Whendrillingsteelapplycuttingoilatthedrillingpoint.

7. Release the pressure slightly,when the drill point pierces the lower surface of themetal. This

preventsthedrillcatchinganddamagingtheworkordrill.

8. Oncompletionofdrillingretracethedrilloutoftheworkandputoffthepowersupply.

Figure1.19:Benchdrill

1.5FINISHINGTOOLS

1.5.1Reamers

Reaming isanoperationof sizingand finishingadrilledhole,with thehelpofa cutting tool

called reamerhaving a number of cutting edges. For this, a hole is first drilled, the sizeofwhich is

slightlysmaller

than

the

finished

size

and

then

ahand

reamer

or

machine

reamer

isused

for

finishing

theholetothecorrectsize.

HandReamerismadeofHighCarbonSteelandhaslefthandspiralflutessothat,itisprevented

fromscrewingintothewholeduringoperation.TheShankendofthereamerismadestraightsothatit

canbeheldinatapwrench.Itisoperatedbyhand,withatapwrenchfittedonthesquareendofthe

reamerandwiththeworkpieceheld inthevice.Thebodyofthereamer isgivenaslighttapperat its

workingend,foritseasyentryintothewholeduringoperation,itisrotatedonlyinclockwisedirection

andalsowhileremovingitfromthewhole.

Figure1.20:Reamers

1.5.2Files

Filingisoneofthemethodsofremovingsmallamountsofmaterialfromthesurfaceofametal

part.Afileishardenedsteeltoo,havingsmallparallelrowsofcuttingedgesorteethonitssurfaces.

Onthefaces,theteethareusuallydiagonaltotheedge.Oneendofthefileisshapedtofitinto

awoodenhandle.The figureshowsvariouspartsofahand file.Thehand file isparallel inwidthand

taperingslightly inthickness,towardsthetip.It isprovidedwithdoublecutteeth.Onthefaces,single

cutononeedgeandnoteethontheotheredge,whichisknownasasafeedge.


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Figure1.21:Partsofahandfile

Filesareclassifiedaccording totheirshape,cutting teethandpitchorgradeofthe teeth.The

figureshowsthevarioustypesoffilesbasedontheirshape.

Figure1.22:Singleanddoublecutfiles

Needlefile

Figure1.23:Typesoffiles


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1.6MISCELLANEOUSTOOLS

1.6.1Filecard

Itisametalbrush,usedforcleaningthefiles,tofreethemfromfilings,cloggedinbetweenthe

teeth.

Figure1.24:Filecard

1.6.2Spiritlevel

Itisusedtocheckthelevelingofmachines.

1.6.3Ball PeenHammer

Ball PeenHammersarenamed,dependingupontheirshapeandmaterialandspecifiedbytheir

weight.Aballpeenhammerhasaflatfacewhich isusedforgeneralworkandaballend,particularly

usedforriveting.

Figure1.25:Ballpeenhammer

1.6.4CrossPeenHammer

It is similar to ball peen hammer, except the shape of the peen. This is used for chipping,

riveting,bendingandstretchingmetalsandhammeringinsidethecurvesandshoulders.

1.6.5StraightPeenHammer

Thisissimilartocrosspeenhammer,but itspeen is inlinewiththehammerhandle.Itisused

forswaging,rivetinginrestrictedplacesandstretchingmetals.

Figure1.26:Crosspeenhammer Figure1.27:Straightpeenhammer

1.6.6Screwdriver

Ascrewdriverisdesignedtoturnscrews.Thebladeismadeofsteelandisavailableindifferent

lengthsanddiameters.Thegrindingofthetiptothecorrectshapeisveryimportant.

Astarscrewdriverisspeciallydesignedtofittheheadofstarscrews.Theendofthebladeisfluted

insteadofflattened.Thescrewdriverisspecifiedbythelengthofthemetalpartfromhandletothetip.


14/5111

Figure1.28:Screwdrivers

1.6.7Spanners

Aspannerorwrenchisatoolforturningnutsandbolts.Itisusuallymadeofforgedsteel.There

aremanykindsofspanners.Theyarenamedaccordingtotheapplication.Thesizeofthespanner

denotesthesizeoftheboltonwhichitcanwork.

Figure1.28:Spanners

1.7SAFEPRACTICE

Thefollowingaresomeofthesafeandcorrectworkpracticesinbenchworkandfittingshop,with

respecttothetoolsused

1.Keephandsandtoolswipedcleanandfreeofdirt,oilandgrease.Drytoolsaresafertousethan

slipperytools.

2.Donotcarrysharptoolsonpockets.

3.Wearleathershoesandnotsandals.

4.Dontwearlooseclothes.

5.Donokeepworkingtoolsattheedgeofthetable.

6.Positiontheworkpiecesuchthatthecuttobemadeisclosetothevice.Thispracticeprevents

springing,sawbreakageandpersonalinjury.

7.Applyforceonlyontheforward(cutting)strokeandrelievetheforceonthereturnstrokewhile

sawingandfiling.

8.Donotholdtheworkpieceinhandwhilecutting.

9.Usethefilewithaproperlyfittedtighthandle.

10.Afterfiling,removetheburrsfromtheedgesofthework,topreventcutstothefingers.

11.Donotuseviceasananvil.


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12.Whilesawing,keepthebladestraight;otherwiseitwillbreak

13.Donotuseafilewithouthandle.

14.Cleantheviceafteruse.

1.8MODELSFORPRACTICE

Preparethemodels,asperthedimensionsandfitsshowninbelow.

Figure1.30:DovetailFitting Figure1.31:Vfitting

Figure1.32:Halfroundfitting Figure1.33:Crossfitting

Figure1.34:DrillingandTapping


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ME101WorkshopPracticeI Fitting

Exercise1SquareFiling

Aim

TofilethegiventwoMildSteelpiecesintoasquareshapeof48mmsideasshowninFigureFE1Toolsrequired

Benchvice,setofFiles,Steelrule,Trysquare,Verniercaliper,Vernierheightgauge,Ballpeenhammer,

Scriber,Dotpunch,Surfaceplate,AngleplateandAnvil.

Sequenceofoperations

1. Thedimensionsofthegivenpiecearecheckedwiththesteelrule.

2. Thejob isfixedrigidly inabenchviceandthetwoadjacentsidesarefiled,usingtheroughflatfile

firstandthenthesmoothflatfilesuchthat,thetwosidesareatrightangle.

3. Therightangleofthetwoadjacentsidesischeckedwiththetrysquare.

4. Chalkisthenappliedonthesurfaceoftheworkpiece.

5. Thegivendimensionsaremarkedbyscribingtwolines,withreferencetotheabovetwodatumsides

byusingVernierheightgauge,AngleplateandSurfaceplate.

6. Usingthe

dot

punch,

dots

are

punched

along

the

above

scribed

lines.

7. Thetwosidesarethenfiled,byfittingthejobinthebenchvice;followedbycheckingtheflatnessof

thesurfaces.

Asthematerialremovalthroughfilingisrelativelyless,filingisdoneinsteadofsawing.ResultThesquarepiecesof48mmsideisthusobtainedbyfiling,asdiscussedabove.

a.Rawmaterial b.Finishedjob

FigureF E1:Squarefiling


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ME101WorkshopPracticeI Fitting

Exercise2VFitting

Aim

TomakeV fitfromthegiventwoMSplates anddrillingandTappingas showninFigureFE2Toolsrequired

Benchvice,setofFiles,Trysquare,Scriber,Steelrule,Ballpeenhammer,Dotpunch,Hacksaw, Vernier

caliper,Surfaceplate,Angleplate,Vernierheightgauge,5mmdrillbit,3mmdrillbit,M6 tapsetwith

wrench,AnvilandDrillingmachine.


1. Theburrsinthepiecesareremovedandthedimensionsarecheckedwithsteelrule.

2. MakebothpiecessurfacelevelsandrightanglesbyfixingintheVice,useFilesforremovingmaterial

togetlevel.

3. WiththehelpofTrysquarechecktherightanglesandsurfacelevels.

4. UsingSurfaceplateandAngleplatemark thegiven twometalpiecesasperdrawingwithVernier

heightgauge.

5. Punch

the

scribed

lines

with

dot

punch

and

hammer

keeping

on

the

Anvil.

Punch

to

punch

give

5

mmgap.

6. CutexcessmaterialwherevernecessarywithHacksawframewithblade,DrillbitsandTaps.

7. The corners and flat surfaces are filed by using square/flat and triangular file to get the sharp

corners.

8. Dimensions are checked by vernier caliper and match the two pieces. Any defect noticed, are

rectifiedbyfilingwithasmoothfile.

9. Care is taken tosee that thepuncheddotsarenotcrossed,which is indicatedby thehalfof the

punchdotsleftonthepieces.

ResultTherequiredV fittingisthusobtained,byfollowingthestages,asdescribedabove.

FigureF E2:VFitting


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Chapter2

CARPENTRY

2.1INTRODUCTION

Carpentrymay be defined as the process ofmaking wooden components. It starts from a

marketableformofwoodandendswithfinishedproducts. It6dealswiththebuildingwork,furniture,

cabinetmaking.Etc.joinery, i.e.,preparationofjoints isoneof the importantoperations inallwood

works.Itdealswiththespecificworkofcarpenterlikemakingdifferenttypesofjointstoformafinished

product.

2.2TIMBER

Timberisthenamegiventothewoodobtainedfromwellgrowntrees.Thetreesarecut,sawn

intovarioussizestosuitbuildingpurposes.

Theword,grain,asappliedtowood,referstotheappearanceorpatternofthewoodonthe

cutsurfaces.Thegrainofthewoodisafibrousstructureandtomake itstrong,thetimbermustbeso

cut,thatthegrainsrunparalleltothelength.

2.2.1Timbersizes

Timbersoldinthemarketisinvarioussizesandshapes.Thefollowingarethecommonshapes

andsizes.

a. Log Thetrunkofthetreewhichisfreefrombranches.

b. Balk Thelog,sawntohaveroughlysquarecrosssection.

c. Post Atimberpiece,roundorsquareincrosssection,havingitsdiameterorside

from175to300mm.

d. Plank Asawntimberpiece,withmorethan275mminwidth,50to150mmin

thicknessand2.5to6.5metersinlength.

e. Board Asawntimberpiece,below175mminwidthand30to50mminthickness.

f. Reapers Sawntimberpiecesofassortedandnonstandardsizes,whichdonotconfirm

totheaboveshapesandsizes.

2.2.2ClassificationofTimber

Wood suitable for construction and other engineering purposes is called timber.Woods in

generalaredividedintotwobroadcategories:SoftwoodsandHardwoods.

Softwoodsareobtainedfromconifers,kair,deodar,chir,walnutandseemal.Woodsobtainedfrom teak, sal,oak, shisham,beach, ashmango,neemandbabulare knownashardwood,but it ishighlydurable.

Another classification ofwoods isbasedon thenameof the trees like teak,babul, shisham,

neem,kair,chir,etc.

2.2.3SeasoningofWood

Anewlyfelledtreecontainsconsiderablemoisturecontent.Ifthisisnotremoved,thetimberis

likely towrap, shrink, crackordecay. Seasoning is the art of extracting themoisture contentunder

controlledconditions,atauniformrate,fromallthepartsofthetimber.Onlyseasonedwoodshouldbe

usedforallcarpentryworks.Seasoningmakesthewoodresilientandlighter.Further,itensuresthatthe

woodwillnotdistortafteritismadeintoanobject.

2.2.4CharacteristicsofGoodTimber

Thegoodtimbermustpossessthefollowingcharacteristics

a. Itshouldhaveminimummoisturecontent,i.e.,thetimbershouldbewellseasoned.

b. Thegrainsofwoodshouldbestraightandlong.

c. Itmustretainitsstraightnessafterseasoning.

d. Itshouldproducenearmetallicsoundonhammering.

e. Itshouldbefreefromknotsorcracks.

f. Itshouldbeofuniformcolor,throughoutthepartofthewood.

g. Itshouldrespondwelltothefinishingandpolishingoperations.

h. Duringdrivingthenailsandscrew,itshouldnotspliteasily.


19/5116

2.3MARKINGANDMEASURINGTOOLS

Accuratemarking andmeasurement is very essential in carpentrywork, toproduceparts to

exact size.To transferdimensionsonto thework; the followingare themarkingandmeasuring tools

thatarerequiredinacarpentryshop.

2.3.1SteelruleandSteeltape

Steelruleisasimplemeasuringinstrumentconsistingofalong,thinmetalstripwithamarked

scaleof

unit

divisions.

Itisan

important

tool

for

linear

measurement.

Steel

tape

isused

for

large

measurements,suchasmarkingonboardsandcheckingtheoveralldimensionsofthework.

Figure2.1:SteelruleandSteeltape2.3.2MarkinggaugeIt isa toolused tomark linesparallel to theedgeofawoodenpiece. Itconsistsofa square

woodenstemwithaslidingwooden stock (head)on it.On thestem is fittedamarkingpin,madeof

steel.Thestockissetatanydesireddistancefromthemarkingpointandfixedinpositionbyascrew.It

mustbeensured thatthemarkingpinprojects throughthestem,about3mmandtheendaresharp

enoughtomakeaveryfineline.Amortisegaugeconsistsoftwopins.Inthis,itispossibletoadjustthedistancebetweenthepins,todrawtwoparallellinesonthestock.

a.Markinggauge b.MortisegaugeFigure2.2:Markinggauges

2.3.3Trysquare

Itisusedformarkingandtestingthesquarenessandstraightnessofplanedsurfaces.Itconsists

ofasteelblade,fittedinacastironstock.Itisalsousedforcheckingtheplanedsurfacesforflatness.Its

sizevariesfrom150to300mm,accordingtothelengthoftheblade.Itislessaccuratewhencompared

tothetrysquareusedinthefittingshop.

Figure2.3:Trysquare

2.3.4Compassanddivider

Compassanddivider,areusedformarkingarcsandcirclesontheplanedsurfacesofthewood.


20/5117

2.3.5Scriberormarkingknife

It isusedformarkingontimber.It ismadeofsteelhavingoneendpointedandtheotherend

formedintoasharpcuttingedge.

2.3.6BevelIt isused for layingoutandcheckingangles.Thebladeof thebevel isadjustableandmaybe

heldinplacebyathumbscrew.Afteritissettothedesiredangle,itcanbeusedinmuchthesameway

asatry

square.

Agood

way

to

set

itto

the

required

angle

isto

mark

the

angle

on

asurface

and

then

adjustthebladetofittheangle.

Figure2.4:CompassandDivider Figure2.5:ScriberandBevel

2.4HOLDINGTOOLS2.4.1Carpenter'svice

Figure2.6showsthecarpenter'sbenchvice,usedasaworkholdingdeviceinacarpentershop.

Itsonejawisfixedtothesideofthetablewhiletheotherismovablebymeansofascrewandahandle.

TheCarpenter'svicejawsarelinedwithhardwooden'faces.

Figure2.6:Carpentersvice Figure2.7:Cclamp

2.4.2Cclamp

Figure2.7showsaCclamp,whichisusedforholdingsmallworks.

2.4.3Barcramp

Figure2.8showsabarcramp. It ismadeofsteelbarofTsection,withmalleable iron fittings

andasteelscrew.Itisusedforholdingwideworkssuchasframesortops.

Figure2.8:barcramp


21/5118

2.5PLANINGTOOLSPlaningistheoperationusedtoproduceflatsurfacesonwood.Aplane isahandtoolusedfor

thispurpose.Thecuttingbladeusedinaplaneisverysimilartoachisel.Thebladeofaplaneisfittedin

awoodenormetallicblock,atanangle.

2.5.1JackplaneIt is themostcommonlyusedgeneralpurposeplane. It isabout35cm long.Thecutting iron

(blade)should

have

acutting

edge

of

slight

curvature.

Itisused

for

quick

removal

of

material

on

rough

workandisalsousedinobliqueplanning.

2.5.2Smoothingplane

Itisusedforfinishingworkandhence,thebladeshouldhaveastraightcuttingedge.Itisabout

20to25cmlong.Beingshort,itcanfolloweventheslightdepressionsinthestock,betterthanthejack

plane.Itisusedafterusingthejackplane.

2.5.3Rebateplane

Itisusedformakingarebate.Arebateisarecessalongtheedgeofapieceofwood,whichis

generallyusedforpositioningglassinframesanddoors.

2.5.4Plough

plane

It isusedtocutgrooves,whichareusedtofixpanels inadoor.Figure2.9showsthevarious

typesofplanesmentionedabove.

Figure2.9:Typesofplanes

2.6CUTTINGTOOLS

2.6.1SawsA saw is used to cutwood into pieces. There are different types of saws, designed to suit

differentpurposes.Asawisspecifiedbythelengthofitstoothededge.

2.6.1.1Crosscutorhandsaw

It isused tocutacross thegrainsof thestock.The teetharesoset that thesawkerfwillbe

widerthanthebladethickness.Thisallowsthebladetomovefreelyinthecut,withoutsticking.


22/5119

2.6.1.2Ripsaw

It isusedforcuttingthestockalongthegrains.Thecuttingedgeofthissawmakesasteeper

angle,i.e.,about60whereasthatofcrosscutsawmakesanangleof45withthesurfaceofthestock.

2.6.1.3Tenonsaw

Itisusedforcuttingthestockeitheralongoracrossthegrains.Itisusedforcuttingtenonsand

infinecabinetwork.However,itisusedforsmallandthincuts.Thebladeofthissawisverythinandso

itisstiffened

with

athick

back

steel

strip.

Hence,

this

issometimes

called

as

back

saw.

In

this,

the

teeth

areshapedlikethoseofcrosscutsaw.

2.6.1.4Compasssaw

Ithasanarrow,longerandstrongertaperingblade,whichisusedforheavyworks(Fig.1.13).It

ismostlyusedinradiuscutting.Thebladeofthissawisfittedwithanopentypewoodenhandle.

Figure2.10:Typesofsaws

2.6.2Chisels

Chiselsareused for cuttingand shapingwoodaccurately.Wood chiselsaremade in various

bladewidths, ranging from3 to50mm.Theyarealsomade indifferentblade lengths.Mostof the

woodchiselsaremadeintotangtype,havingasteelshankwhichfitsinsidethehandle.Thesearemade

offorgedsteelortoolsteelblades.

Figure2.11:Partsofchisel


23/5120

2.6.2.1Firmerchisel

Theword'firmer'means'stronger'andhencefirmerchiselisstrongerthanotherchisels.Itisa

generalpurposechiselandisusedeitherbyhandpressureorbyamallet.Thebladeofafirmerchiselis

flat,asshowninFigure2.12a.

2.6.2.2Dovetailchisel

Ithasabladewithabeveledback,asshowninFigure,duetowhichitcanentersharpcomers

forfinishing,

as

in

dovetail

joints.

2.6.2.3Mortisechisel

It isusedforcuttingmortisesandchipping insideholes,etc.Thecrosssectionofthemortisechisel is

proportioned towithstandheavyblowsduringmortising.Further, thecrosssection ismade stronger

neartheshank.

a.Firmer b.Dovetail c.MortiseFigure2.12: Typesofchisels

2.7 DRILLINGANDBORINGTOOLS2.7.1Carpentersbrace

It isused forrotatingaugerbits, twistdrills,etc., toproduceholes inwood. Insomedesigns,

braces are made with ratchet device.With this, holesmay bemade in a corner where complete

revolutionofthehandlecannotbemade.Thesizeofabraceisdeterminedbyitssweep.

2.7.2AugerbitIt isthemostcommontoolused formakingholes inwood.Duringdrilling,the leadscrewof

thebitguides intothewood,necessitatingonlymoderatepressureonthebrace.Thehelicalfluteson

thesurfacecarrythechipstotheoutersurface.

2.7.3HanddrillCarpenter's brace is used tomake relatively large size holes;whereashand drill isused for

drillingsmallholes.Astraightshankdrill isusedwith this tool. It issmall, light inweightandmaybe

convenientlyused than thebrace.Thedrillbit isclamped in thechuckat itsendand is rotatedbya

handleattachedtogearandpinionarrangement.

2.7.4Gimlet

Ithascuttingedges likea twistdrill. It isused fordrilling largediameterholeswith thehand

pressure.


24/5121

Figure2.13: Drillingtools

2.8MISCELLANEOUS

TOOLS

2.8.1MalletItisusedtodrivethechisel,whenconsiderableforceistobeapplied,whichmaybethecasein

makingdeeproughcuts.Steelhammershouldnotbeusedforthepurpose,asitmaydamagethechisel

handle.Further,forbettercontrol,itisbettertoapplyaseriesoflighttapswiththemalletratherthana

heavysingleblow.

2.8.2PincerIt ismadeof two forgedsteelarmswithahingedjointand isused forpullingoutsmallnails

fromwood.Theinnerfacesofthepincerjawsarebeveledandtheouterfacesareplain.Theendofone

armhasaballandtheotherhasaclaw.Thebeveledjawsandtheclawareusedforpullingoutsmall

nails,pinsandscrewsfromthewood.

2.8.3ClawhammerIthasastrikingflatfaceatoneendand theclawattheother,asshown in figure.Theface is

usedtodrivenailsintowoodandforotherstrikingpurposesandtheclawforextractingrelativelylarge

nailsoutofwood.Itismadeofcaststeelandweighsfrom0.25kgto0.75kg.

2.8.4Screwdriver

Itisusedfordrivingscrews intowoodorunscrewingthem.Thescrewdriverofacarpenter is

differentfromtheothercommontypes,asshowninfigure.

The length of a screw driver is determined by the length of the blade. As the length of the blade

increases,thewidthandthicknessofthetipalsoincrease.

2.8.5WoodraspfileIt isa finishingtoolusedtomakethewoodsurfacesmooth,removesharpedges, finishfilletsandotherinteriorsurfaces.Sharpcuttingteethareprovidedonits

surfaceforthepurpose.Thisfileisexclusivelyusedinwoodwork.

2.8.6BradawlItisahandoperatedtool,usedtoboresmallholesforstartingascreworlargenail.


25/5122

a.Mallet b.Pincer c.Clawhammer d.Bradawl

e.Woodraspfile f.Screwdriver

Figure2.14:Miscellaneoustools

2.9WOODJOINTS

Therearemanykindsofjointsused toconnectwoodstock.Eachjointhasadefiniteuseand

requires lay inout,cutting them together.Thestrengthof thejointdependsuponamountofcontactarea.Ifaparticularjointdoesnothavemuchcontactarea,thenitmustbereinforcedwithnails,screws

ordowels.Thefigure2.15showssomecommonlyusedwoodjoints.

a.Butt b.Dowell c.Dado d.Rabbet

e.Lap f.Mortiseandtenon g.Miter

Figure2.15: Commonwoodjoints

2.9.1Lapjoints

Inlapjoints,anequalamountofwoodisremovedfromeachpiece,asshowninfigure2.16.Lap

jointsareeasyto layout,usingatrysquareandamarkinggauge.Followtheproceduresuggestedfor

sawingandremovingthewastestock.Ifthejointisfoundtobetootight,itisbettertoreducethewidth

of thematingpiece, insteadof trimming theshoulderof thejoint.This typeofjoint isused forsmall

boxestolargepiecesoffurniture.


26/5123

Figure2.16:Lapjoints

2.9.2MortiseandTenonJoints

It is used in the construction of quality furniture. It results in a strong joint and requires

considerableskilltomakeit.Thefollowingarethestagesinvolvedinthework.

a. Markthemortiseandtenonlayouts.

b. Cutthemortisefirstbydrillingseriesofholeswithinthe layout line,chiselingoutthewastestock

andtrimmingthecornersandsides.

c. Preparethetenonbycuttingandchiseling.

d. Checkthetenonsizeagainstthemortisethathasbeenpreparedandadjustitifnecessary.

Figure2.17:Mortiseand Tenonjoints

2.9.3Bridlejoint

Thisisthereverseofmortiseandtenonjointinform.Themarkingoutofthejointisthesameas

formortiseandtenonjoint.Thisjointisusedwherethemembersareofsquareornearsquaresection

andunsuitableformortiseandtenonjoint.

Figure2.18: Bridlejoint


27/5124

2.10SAFEPRACTICE

Thefollowingaresomeofthesafeandcorrectworkpracticesincarpentryshop,withrespectto

thetoolsused

1. Toolsthatarenotbeingusedshouldalwaysbekeptattheirproperplaces.

2. Makesurethatyourhandsarenotinfrontofsharpedgedtoolswhileyouareusingthem.

3. Useonlysharptools.Adulltoolrequiresexcessivepressure,causingthetooltoslip.

4. Woodenpieceswithnails,shouldneverbeallowedtoremainonthefloor.

5. Becareful

when

you

are

using

your

thumb

as

aguide

in

cross

cutting

and

ripping.

6. Testthesharpnessofthecuttingedgeofchiselonwoodorpaper,butnotonyourhand.

7. Neverchiseltowardsanypartofthebody.

8. Donotusechiselswherenailsarepresent.Donotusechiselasascrewdriver.

9. Donotuseasawwithaloosehandle.

10.Alwaysusetriangularfileforsharpeningtheteeth.

11.Donotuseasawonmetallicsubstances.

12.Donotusemallettostrikenails.

13.Donotuseplaneattheplaces,whereanailisdriveninthewood.


28/5125

ME101WorkshopPracticeI Carpentry

Exercise1TLapjoint

Aim

TomakeaTlapjointasshowninFigure2.19,fromthegivenreaperofsize50x35x250mm.Toolsrequired

Carpenter'svice,steelrule,jackplane, trysquare,markinggauge,25mm firmerchisel,crosscutsaw,

tenonsaw,scriberandmallet.


1. Thegivenreaperischeckedtoensureitscorrectsize.

2. Thereaper isfirmlyclamped inthecarpenter'sviceandanytwoadjacentfacesareplanedbythe

jackplaneandthetwofacesarecheckedforsquarenesswiththetrysquare.

3. Markinggaugeissetandlinesaredrawnat30and45mm,tomarkthethicknessandwidthofthe

modelrespectively.

4. Theexcessmaterialisfirstchiseledoutwithfirmerchiselandthenplanedtocorrectsize.

5. ThematingdimensionsofthepartsXandYarethenmarkedusingscaleandmarkinggauge

6. Usingthecrosscutsaw,theportionstoberemovedarecutinboththepieces,followedbychiselingandalsothepartsXandYareseparatedbycrosscutting,usingthetenonsaw

7. Theendsofboththepartsarechiseledtotheexactlengths.

8. Afinefinishingisgiventotheparts,ifrequiredsothat,properfittingisobtained.

9. Thepartsarefittedtoobtainaslightlytightjoint.

Result TheTLapjointisthusmadebyfollowingtheabovesequenceofoperations.

FigureC E1: T lapjoint


29/5126


Exercise2Dovetaillapjoint

Aim

TomakeadovetaillapjointasshowninFigure2.20,fromthegivenreaperofsize50x35x250mm.Toolsrequired

Carpentersvice,steelrule,jackplane,trysquare,markinggauge,25mm firmerchisel,crosscutsaw,

tenonsaw,scriberandmallet.



2. Thereaper isfirmlyclamped inthecarpenter'sviceandanytwoadjacentfacesareplanedbythe

jackplaneandthetwofacesarecheckedforsquarenesswiththetrysquare.

3. Markinggaugeissetandlinesaredrawnat30anc145mm,tomarkthethicknessandwidthofthe

modelrespectively.

4. Theexcessmaterialisfirstchiseledoutwithfirmerchiselandthenplanedtocorrectsize.

5. ThematingdimensionsofthepartsXandYarethenmarkedusingscaleandmarkinggauge.

6. Usingthecrosscutsaw,theportionstoberemovedarecutinboththepieces,followedbychiselingandalsothepartsXandYareseparatedbycrosscutting,usingthetenonsaw.

7. Theendsofboththepartsarechiseledtoexactlengths.

8. Afinefinishingisgiventotheparts,ifrequiredsothat,properfittingisobtained.

9. Thepartsarefittedtoobtainaslightlytightjoint.

Result Thedovetaillapjointisthusmadebyfollowingtheabovesequenceofoperations.

FigureC E2:Dovetaillapjoint


30/5127


Exercise3MortiseandTenonjoint

Aim

TomakeamortiseandtenonjointasshowninFig.1.34b,fromthegivenreaperofsize50x35x250mm.

Toolsrequired

Carpenter'svice,steelrule,jackplane,trysquare,markinggauge,25111mfirmerchisel,6mmmortisechisel,crosscutsaw,tenonsaw,scriberandmallet.



2. Thereaperisfirmlyclampedinthecarpenter'sviceandoneofitsfacesareplanedbythejackplane

andcheckedforstraightness.

3. Theadjacentfaceisthenplanedandthefacesarecheckedforsquarenesswiththetrysquare.

4. Markinggaugeissetandlinesaredrawnat30and45mm,tomarkthethicknessandwidthofthe

modelrespectively.

5. Theexcess

material

isfirst

chiseled

out

with

the

firmer

chisel

and

then

planed

to

correct

size.

6. ThematingdimensionsofthepartsXandYarethenmarkedusingthescaleandmarkinggauge.

7. Usingthecrosscutsaw,theportionstoberemovedinpartY(tenon)iscut,followedbychiseling.

8. ThematerialtoberemovedinpartX(mortise)iscarriedoutbyusingthemortise

andfirmerchisels.

9. ThepartsXandYareseparatedbycrosscuttingwiththetenonsaw

10.Theendsofboththepartsarechiseledtoexactlengths.

11.Finishchiselingisdonewhereverneededsothat,thepartscanbefittedtoobtainaneartightjoint.

Result Themortiseandtenonjointisthusmadebyfollowingtheabovesequenceofoperations.

FigureCE3: MortiseandTenonjoint


31/5128

Chapter3

WELDING

3.1 INTRODUCTION

Welding is the process ofjoining similarmetals by the application of heat,with orwithout

applicationofpressureor fillermetal, in such away that thejoint is equivalent in composition and

characteristicsofthemetalsjoined.Inthebeginning,weldingwasmainlyusedforrepairingallkindsofwornordamagedparts.Now, it is extensivelyused inmanufacturing industry, construction industry

(constructionof ships, tanks, locomotivesandautomobiles)andmaintenancework, replacing riveting

andbolting,toagreaterextent.

Thevariousweldingprocessesare:

1. Electricarcwelding,

2. Gaswelding

3. Thermalwelding

4. ElectricalResistanceweldingand

5. Frictionwelding

However,onlyelectricarcweldingprocessisdiscussedinthesubjectpointofview.

3.2ELECTRICARCWELDING

Arcweldingistheweldingprocess,inwhichheatisgeneratedbyanelectricarcstruckbetweenanelectrodeand theworkpiece.Electricarc is luminouselectricaldischargebetween twoelectrodes

throughionizedgas.

Figure3.1:Arcweldingsetup.

Anyarcweldingmethodisbasedonanelectriccircuitconsistingofthefollowingparts:

a. Powersupply(ACorDC);b. Weldingelectrode;c. Workpiece;

d. Weldingleads(electriccables)connectingtheelectrodeandworkpiecetothepowersupply.Electric arc between the electrode and work piece closes the electric circuit. The arc

temperaturemayreach10000F(5500C),whichissufficientforfusiontheworkpieceedgesandjoining

them. Whena longjoint isrequiredthearc ismovedalongthejoint line.The frontedgeoftheweld

poolmeltstheweldedsurfaceswhentherearedgeoftheweldpoolsolidifiesformingthejoint.

Transformers,motor generators and rectifiers sets areused as arcweldingmachines. These

machinessupplyhighelectriccurrentsatlowvoltageandanelectrodeisusedtoproducethenecessary

arc.Theelectrodeservesasthefillerrodandthearcmeltsthesurfacesothat,themetalstobejoined

areactuallyfixedtogether.

Sizesofweldingmachinesareratedaccordingtotheirapproximateamperagecapacityat60%

duty cycle, such as 150,200,250,300,400,500 and 600 amperes. This amperage is the rated current

outputattheworkingterminal.


32/5129

3.2.1Transformers

The transformers typeofweldingmachineproducesA.C currentand isconsidered tobe the

leastexpensive.Ittakespowerdirectlyfrompowersupplylineandtransformsittothevoltagerequired

forwelding.Transformersareavailableinsinglephaseandthreephasesinthemarket.

3.2.2Motorgenerators

TheseareD.Cgeneratorssets,inwhichelectricmotorandalternatoraremountedonthesame

shaft toproduceD.Cpoweraspert the requirement forwelding.Thesearedesigned toproduceD.C

currentin

either

straight

or

reversed

polarity.

The

polarity

selected

for

welding

depends

upon

the

kind

ofelectrodeusedandthematerialtobewelded.

3.2.3Rectifiers

Theseareessentiallytransformers,containinganelectricaldevicewhichchangesA.CintoD.Cby

virtueofwhichtheoperatorcanusebothtypesofpower(A.CorD.C,butonlyoneatatime).Inaddition

totheweldingmachine,certainaccessoriesareneededforcarryingouttheweldingwork.

3.2.4Weldingcables

Twowelding cables are required, one frommachine to the electrodeholder and theother,

fromthemachinetothegroundclamp.Flexiblecablesareusuallypreferredbecauseofthecaseofusing

andcoilingthecables.Cablesarespecifiedbytheircurrentcarryingcapacity,say300A,400A,etc.

3.2.5Electrodes

Fillerrodsareusedinarcweldingarecalledelectrodes.Thesearemadeofmetallicwirecalled

corewire,

having

approximately

the

same

composition

as

the

metal

to

be

welded.

These

are

coated

uniformlywithaprotectivecoatingcalledflux.Whilefluxinganelectrode;about20mmoflengthisleft

atoneendforholding itwiththeelectrodeholder. Ithelps intransmittingfullcurrentfromelectrode

holdertothefrontendoftheelectrodecoating.Fluxactsasan insulatorofelectricity.Figure.4shows

thevariouspartsofanelectrode.

Figure3.2:Partsofanelectrode

Ingeneral,electrodesareclassifiedintofivemaingroups;mildsteel,carbonsteel,specialalloy

steel,cast ironandnonferrous.Thegreatestrangeofarcwelding isdonewithelectrodes inthemild

steelgroup.

Variousconstituents liketitaniumoxide,potassiumoxide,cellulose, ironormanganese,Ferro

silicates,carbonates,gums,clays,asbestos,etc.,areusedascoatingsonelectrodes.Whilewelding,the

coatingorfluxvaporizesandprovidesagaseousshieldtopreventatmosphericattack.

ThesizeofelectrodeismeasuredanddesignatedbythediameterofthecorewireinSWGand

length,apartfromthebrandandcodenames;indicatingthepurposeforwhichtherearemostsuitable.Electrodesmaybeclassifiedonthebasisofthicknessofthecoatedflux.As

1. Dustcoatedorlightcoated

2. Semiormediumcoatedand

3. Heavilycoatedorshielded

Electrodesarealsoclassifiedonthebasisofmaterials,as

1. Metallicand

2. Nonmetallicorcarbon

Metallicarcelectrodesarefurthersubdividedinto

1. Ferrousmetalarcelectrode(mildsteel,low/medium/highcarbonsteel,castiron,stainlesssteel,etc)

2. Nonferrousmetalarcelectrodes(copper,brass,bronze,aluminum,etc).

Incaseofnonmetallicarcelectrodes,mainlycarbonandgraphiteareusedtomaketheelectrodes.


33/5130

3.3WELDINGTOOLS

3.3.1Electrodeholder

Theelectrodeholder isconnected to theendof theweldingcableandholds theelectrode. It

shouldbelight,strongandeasytohandleandshouldnotbecomehotwhileinoperation.Figureshows

one typeof electrodeholder.Thejawsof theholder are insulated,offeringprotection fromelectric

shock.

Figure3.3:Electrodeholder Figure3.4:Groundclamp

3.3.2Groundclamp

Itisconnectedtotheendofthegroundcableandisclampedtotheworkorweldingtabletocompletetheelectriccircuit.Itshouldbestronganddurableandgivealowresistanceconnection.

3.3.3Wirebrushandchippinghammer

Awirebrushisusedforcleaningandpreparingtheworkforwelding.Achippinghammerisused

forremovingslagformationonwelds.Oneendoftheheadissharpenedlikeacoldchiselandtheother,

toablunt,roundpoint. It isgenerallymadeoftoolsteel.Moltenmetaldispersedaroundthewelding

heads,intheformofsmalldrops,isknownasspatter.Whenafluxcoatedelectrodeisusedinwelding

process,thenalayeroffluxmaterial isformedovertheweldingbeadwhichcontainstheimpuritiesof

weldmaterial.This layer isknownas slag.Removing the spatterandslag formedonandaround the

weldingbeadsonthemetalsurfaceisknownaschipping.

Figure3.5:Wirebrush Figure3.6:Chippinghammer

3.3.4Weldingtableandcabin

It ismadeofsteelplateandpipes. It isused forpositioning theparts tobeweldedproperly.

Weldingcabinismadeupbyanysuitablethermalresistancematerial,whichcanisolatethesurrounding

bytheheatandlightemittedduringtheweldingprocess.Asuitabledraughtshouldalsobeprovidedforexhaustingthegasproducedduringwelding.

3.3.5Faceshield

Afaceshield isusedtoprotecttheeyesandfacefromtheraysofthearcandfromspatteror

flyingparticlesofhotmetal.Itisavailableeitherinhandorhelmettype.Thehandtypeisconvenientto

usewherevertheworkcanbedonewithonehand.Thehelmettypethoughnotcomfortabletowear,

leavesbothhandsfreeforthework.

Shieldsaremadeoflightweightnonreflectingfiberandfittedwithdarkglassestofilteroutthe

harmfulraysofthearc.Insomedesigns,acoverglassisfittedinfrontofthedarklenstoprotectitfrom

spatter.


34/5131

3.3.6Handgloves

Theseareusedtoprotectthehandsfromelectricshocksandhotspatters

Handheldtype Helmettype

Figure3.7:Handgloves Figure3.8:Faceshield

3.4TECHNIQUESOFWELDING

3.4.1Preparationofwork

Beforewelding, theworkpiecesmustbe thoroughly cleanedof rust, scaleandother foreign

material.Thepieceformetalgenerallyweldedwithoutbevelingtheedges,however,thickworkpiece

shouldbebeveledorveedouttoensureadequatepenetrationandfusionofallpartsoftheweld.But,in

eithercase,thepartstobeweldedmustbeseparatedslightlytoallowbetterpenetrationoftheweld.

Beforecommencingtheweldingprocess,thefollowingmustbeconsidered

a) Ensurethattheweldingcablesareconnectedtoproperpowersource.

b) Settheelectrode,asperthethicknessoftheplatetobewelded.

c) Settheweldingcurrent,asperthesizeoftheelectrodetobeused.

Table3.1ElectrodecurrentVselectrodesizeVsplatethickness.

Platethickness,mm Electrodesize,mm Electrodecurrentrange,amp

1.6

2.5

4.0

6.0

8.0

25.0

1.6

2.5

3.2

4.0

5.0

6.0

4060

5080

90130

120170

180270

300400

NOTE:Whilemakingbuttweldsinthinmetal,itisabetterpracticetotackweldthepiecesintervalsto

holdthemproperlywhilewelding.

3.4.2Strikinganarc

Thefollowingarethestagesandmethodsofstrikinganarcandrunninga beada) Selectanelectrodeofsuitablekindandsize fortheworkandset theweldingcurrentataproper

value.

b) Fastenthegroundclamptoeithertheworkorweldingtable.

c) Startorstrikethearcbyeitherofthefollowingmethods

Strikeandwithdraw

Inthismethodthearcisstartedbymovingtheendoftheelectrodeontotheworkwithaslow

sweepingmotion,similartostrikingamatch.

Touchandwithdraw

Inthismethod,thearcisstartedbykeepingtheelectrodeperpendicularto theworkand

touchingorbouncingitlightlyonthework.Thismethodispreferredasitfacilitatesrestartingthe


35/5132

momentarilybrokenarcquickly. Iftheelectrodestickstothework,quicklybenditbackandforth,

pullingatthesametime.Makesuretokeeptheshieldinfrontoftheface,whentheelectrodeis

freedfromsticking.

d) Assoonasthearc isstruck,movetheelectrodealong,slowlyfrom lefttoright,keepingat15to

25fromverticalandinthedirectionofwelding.

Strikeandwithdraw Touchandwithdraw

Figure3.9: strikinganarc

3.4.3Weaving

A steady,uniformmotionof the electrodeproduces a satisfactorybead.However, a slight

weavingoroscillatingmotionispreferred,asthiskeepsthemetalmoltenalittlelongerandallowsthe

gas to escape, bringing the slag to the surface. Weaving also produces a wider bead with better

penetration.

3.5TYPESOFJOINTS

Weldsaremadeatthejunctionofthevariouspiecesthatmakeuptheweldment.Thejunctions

ofparts,orjoints,aredefinedasthelocationwheretwoormorenumbersaretobejoined.Partsbeing

joinedtoproducetheweldmentmaybe intheformofrolledplate,sheet,pipes,castings,forgings,or

billets.Thefivebasictypesofjointsarelistedbelow.

Figure3.10: Typesofweldingjoints.

Abuttjointisusedtojointwomembersalignedinthesameplane(fig.3.10,viewA).Thisjointis

frequently used in plate, sheetmetal, and pipework. Ajoint of this typemay be either square or

grooved.


36/5133

Cornerandteejointsareusedtojoin twomembers locatedatrightanglestoeachother(fig.

3.10,viewsBandC).Incrosssection,thecornerjointformsanLshape,andtheteejointhastheshape

oftheletterT.Variousjointdesignsofbothtypeshaveusesinmanytypesofmetalstructures.

Alapjoint,asthename implies,ismadebylappingonepieceofmetaloveranother(fig.3.10,

viewD).Thisisoneofthestrongesttypesofjointsavailable;however,formaximumjointefficiency,you

shouldoverlap themetalsaminimumof three times the thicknessof the thinnestmember you are

joining.Lapjointsarecommonlyusedwithtorchbrazingandspotweldingapplications.

Anedge

joint

isused

to

join

the

edges

of

two

or

more

members

lying

in

the

same

plane.

In

most

cases,oneofthemembersisflanged,asshowninfigure3.10,viewE.Whilethistypeofjointhassome

applicationsinplatework,itismorefrequentlyusedinsheetmetalwork. Anedgejointshouldonlybe

usedforjoiningmetals1/4inchorlessinthicknessthatarenotsubjectedtoheavyloads.

3.6WELDINGPOSITIONS

Dependingupon the locationof theweldingjoints,appropriatepositionof theelectrodeand

handmovementisselected.Thefigureshowsdifferentweldingpositions.

Figure3.11: Weldingpositions

3.6.1Flatpositionwelding

Inthisposition,theweldingisperformedfromtheuppersideofthejoint,andthefaceoftheweld

is approximately horizontal. Flat welding is the preferred term; however, the same position is

sometimescalleddownhand.

3.6.2Horizontalpositionwelding

In thisposition,welding isperformedon theuppersideofanapproximatelyhorizontalsurface

andagainstanapproximatelyverticalsurface.

3.6.3Verticalpositionwelding

Inthisposition,theaxisoftheweldisapproximatelyverticalasshowninfigure.

3.6.4Overheadpositionwelding

Inthisweldingposition,theweldingisperformedfromtheundersideofajoint.

3.7 ADVANTAGES&DISADVANTAGESOFARCWELDING

Advantages

1.Weldingprocessissimple.

2. Equipmentisportableandthecostisfairlylow.

3. Alltheengineeringmetalscanbeweldedbecauseoftheavailabilityofawidevarietyofelectrodes.

Disadvantages

1. Mechanizedweldingisnotpossiblebecauseoflimitedlengthoftheelectrode.

2. Numberofelectrodesmayhavetobeusedwhileweldinglongjoints.

3. Adefect(slaginclusionorinsufficientpenetration)mayoccurattheplacewhereweldingisrestarted

withafreshelectrode.


37/5134

3.8SAFEPRACTICE

Alwaysweld inawellventilatedplace.Fumesgivenofffromweldingareunpleasantand insome

casesmaybeinjurious,particularlyfromgalvanizedorzinccoatedparts.

1. Donotweldaroundcombustibleorinflammablematerials,wheresparksmaycauseafire.

2. Neverweldcontainers,whichhavebeenusedforstoringgasoline,oilorsimilarmaterials,without

firsthavingthemthoroughlycleaned.

3. Check theweldingmachine tomake sure that it isproperlygroundedand thatall leadsproperly

insulated.

4. Never lookatthearcwiththenakedeye.Thearccanburnyoureyesseverely.Alwaysusea face

shieldwhilewelding.

5. Preventweldingcablesfromcomingincontactwithhotmetal,water,oil,orgrease.Avoiddragging

thecablesaroundsharpcorners.

6. Ensureproperinsulationofthecablesandcheckforopenings.

7. Alwayswearthesafetyhandgloves,apronandleathershoes.

8. Alwaysturnoffthemachinewhenleavingthework.

9. Applyeyedropsafterweldingisoverfortheday,torelievethestrainontheeyes.

10.Whilewelding,standondryfootingandkeepthebodyinsulatedfromtheelectrode,anyotherparts

oftheelectrodeholderandthework.


38/5135

ME101WorkshopPracticeI Welding

Exercise1SingleV Buttjoint

Aim

Tomakeasinglevbuttjoint,usingthegivenmildsteelpiecesof andbyarcwelding.Materialused

Twomildsteelpiecesof100X40X6mm.

Toolsandequipmentused

Arcweldingmachine,Mildsteelelectrodes,Electrodeholder,Groundclamp,flatnoseTong,Faceshield,

Apron,Handgloves,MetallicworkTable,Benchvice,Roughflatfile,Trysquare,Steelrule,Wirebrush,

Ballpeenhammer,Chippinghammer,ChiselandGrindingmachine.

Sketch

Figure3.12: SingleVbuttjoint

Operationstobecarriedout

1. Cleaningtheworkpieces

2. tackwelding

3. fullwelding

4. cooling

5. chipping

6. finishing

Procedure

1. Takethetwomildsteelpiecesofgivendimensionsandcleanthesurfacesthoroughlyfromrust,dust

particles,oilandgrease.

2. Removethesharpcornersandburrsbyfilingorgrinding.

3. Oneedgeofeachpieceisbeveled,toanangle30.

4. Thetwopiecesarepositionedontheweldingtablesuchthat,theyareseparatedslightlyforbetter

penetrationoftheweld.

5. Theelectrodeisfittedintotheelectrodeholderandtheweldingcurrentissettoapropervalue.

6. Thegroundclampisfastenedtotheweldingtable.ThemachineisswitchedON

7. Wearingtheapron,handgloves,usingthefaceshield,thearcisstruckandtheworkpiecesaretack

weldedattheendsandholdingthetwopiecestogether;firstrunoftheweldisdonetofilltheroot

gap.

8. Secondrunoftheweldingisdonewithproperweavingandwithuniformmovement.Duringthe

processofwelding,theelectrodeiskeptatangleof15to25fromverticalandinthedirectionof

welding.

9. Theslagformationontheweldisremovedbychippinghammer.

10.Filingisdonetoremovespattersaroundtheweld.

Result Thesinglevbuttjointisthusmade,usingthetoolsandequipmentasmentionedabove.


39/5136


Exercise2Double Lapjoint

Aim

Tomakeadoublelapjoint,usingthegivenmildsteelpiecesandbyarcwelding.Materialused






Sketch

Figure3.13: Doublelapjoint



2. tackwelding

3. fullwelding

4. cooling5. chipping

6. finishing

Procedure



2. Removethesharpcornersandburrsbyfilingorgrindingandpreparetheworkpieces.

3. Theworkpiecesarepositionedontheweldingtable,toformalapjointwiththerequiredover

lapping.


5. Thegroundclampisfastenedtotheweldingtable.

6. Wearingtheapron,handgloves,usingthefaceshieldandholdingtheoverlappedpiecesthearcis

struckandtheworkpiecesaretackweldedattheendsof boththesides7. Thealignmentofthelapjointischeckedandthetackweldedpiecesarereset,ifrequired.

8. Weldingisthencarriedoutthroughoutthelengthofthelapjoint,onboththesides.

9. Removetheslag,spattersandcleanthejoint.

Result Thedoublelapjointisthusmade,usingthetoolsandequipmentasmentionedabove.


40/5137


Exercise3Cornerjoint

Aim

Tomakeacornerjoint,usingthegivenmildsteelpiecesandbyarcwelding.Materialused






Sketch

Figure3.14: Cornerjoint



2. tackwelding

3. fullwelding

4. cooling

5. chipping

6. finishing

Procedure




3. Theworkpiecesarepositionedontheweldingtablesuchthat,theLshapeisformed.



6. Wearingtheapron,handgloves,usingthefaceshieldandholdingthepiecesthearcisstruckand

theworkpiecesaretackweldedatboththeends.

7. Thealignmentofthecornerjointischeckedandthetackweldedpiecesarereset,ifrequired.

8. Weldingisthencarriedoutthroughoutthelength.


Result TheCornerjointisthusmade,usingthetoolsandequipmentasmentionedabove.


41/5138


Exercise4Tjoint

Aim

TomakeaTjoint,usingthegivenmildsteelpiecesandbyarcwelding.Materialused






Sketch

Figure3.15: Tjoint



2.tackwelding

3. fullwelding

4. cooling

5. chipping

6. finishing

Procedure




3. Theworkpiecesarepositionedontheweldingtablesuchthat,theTshapeisformed.



6. Wearingtheapron,handgloves,usingthefaceshieldandholdingthepiecesthearcisstruckand

theworkpiecesaretackweldedatboththeends.

7. ThealignmentoftheTjointischeckedandthetackweldedpiecesarereset,ifrequired.

8. WeldingisthencarriedoutthroughoutthelengthoftheTjointasshowninthefigure.


Result TheTeejointisthusmade,usingthetoolsandequipmentasmentionedabove.


42/5139

Chapter4

MACHINESHOP

4.1INTRODUCTION

Inamachineshop,metalsarecuttoshapeondifferentmachinetools.Alatheisusedtocutand

shape themetalby revolving theworkagainstacutting tool.Thework isclampedeither inachuck,

fittedontothelathespindleorinbetweenthecenters.Thecuttingtoolisfixedinatoolpost,mountedonamovablecarriagethat ispositionedonthe lathebed.Thecuttingtoolcanbefedontothework,

either lengthwiseorcrosswise.While turning,thechuckrotates incounterclockwisedirection,when

viewedfromthetailstockend.

4.2PRINCIPALPARTSOFALATHE

Figure4.1showsacenterlathe,indicatingthemainparts.Thenameisduetothefactthatwork

piecesareheldbythecenters.

Figure4.1: Partsofacenterlathe

4.2.1Bed

It is an essential part of a lathe,whichmust be strong and rigid. It carries all parts of themachine and resists the cutting forces. The carriage and the tail stockmove along the guideways

providedonthebed.Itisusuallymadeofcastiron.

4.2.2Headstock

Itcontainseitheraconepulleyorgearingstoprovidethenecessaryrangeofspeedsandfeeds.

Itcontainsthemainspindle,towhichtheworkisheldandrotated.

4.2.3Tailstock

Itisusedtosupporttherighthandendofalongworkpiece.Itmaybeclampedinanyposition

alongthe lathebed.Thetailstockspindlehasan internalMorsetapertoreceivethedeadcenterthat

supportsthework.Drills,reamers,tapsmayalsobefitted intothespindle,forperformingoperations

suchasdrilling,reamingandtapping.

4.2.4CarriageorSaddle

It isused tocontrol themovementof thecutting tool.Thecarriageassemblyconsistsof the

longitudinalslide,crossslideandthecompoundslideandapron.Thecrossslidemovesacrossthelength

ofthebedandperpendiculartotheaxisofthespindle.Thismovementisusedforfacingandtoprovide

thenecessarydepthofcutwhileturning.Theapron,whichisboltedtothesaddle,isonthefrontofthe

latheandcontainsthelongitudinalandcrossslidecontrols.

4.2.5CompoundRest

Itsupportsthetoolpost.Byswivelingthecompoundrestonthecrossslide,shorttapersmaybe

turnedtoanydesiredangles.


43/5140

4.2.6ToolPost

Thetoolpost,holdsthetoolholderorthetool,whichmaybeadjustedtoanyworkingposition.

4.2.7LeadScrew

Itisalongthreadedshaft,locatedinfrontofthecarriage,runningfromtheheadstocktothe

tailstock.Itisgearedtothespindleandcontrolsthemovementofthetool,eitherforautomaticfeeding

orforcuttingthreads.

4.2.8Centers

Therearetwocentersknownasdeadcenterand livecenter.Thedeadcenter ispositioned in

thetailstockspindleandthelivecenter,intheheadstockspindle.Whileturningbetweencenters,the

deadcenterdoesnotrevolvewiththeworkwhilethelivecenterrevolveswiththework.

4.3WORKHOLDINGDEVICES

4.3.1Threejawchuck

It is awork holding device having threejaws (selfcentering)whichwill close or openwith

respect to the chuck center or the spindle center, as shown in figure. It is used for holding regular

objectslikeroundbars,hexagonalrods,etc.

Figure4.2: Threejawchuck Figure4.3: Fourjawchuck

4.3.3Faceplate

Itisaplateoflargediameter,usedforturningoperations.Certaintypesofworkthatcannotbe

heldinchucksareheldonthefaceplatewiththehelpofvariousaccessories.

Figure4.4: Faceplate Figure4.5: Lathedoganddrivingplate

4.3.4Lathedogsanddrivingplate

Theseareusedtodriveaworkpiecethatisheldbetweencenters.Theseareprovidedwithan

opening to receive and clamp thework piece and dog tail, the tail of the dog is carried by the pin

providedinthedrivingplatefordrivingtheworkpiece.

4.4MEASURINGINSTRUMENTS

4.4.1OutsideandinsideCalipers

Firmjointorspringcalipersareusedfortransferofdimensionswiththehelpofasteelrule.


44/5141

Figure4.6: Calipers

4.4.2VernierCalipers

Verniercaliperisaversatileinstrumentwithwhichbothoutsideandinsidemeasurementsmay

bemadeaccurately.Theseinstrumentsmayhaveprovisionfordepthmeasurementalso.

Figure4.7: VernierCaliper

4.4.3Micrometers

Outsideand insidemicrometersareusedformeasuringcomponentswheregreateraccuracyis

required.

4.5CUTTINGPARAMETERS

4.5.1Cuttingspeed

It is defined as the speed atwhich thematerial is removed and is specified inmeters per

minute.Tidependsupon theworkpiecematerial, feed,depthofcut, typeofoperationandsomany

othercuttingconditions.Itiscalculatedfromtherelation,

Spindlespeed(RPM)=cuttingspeedx1000/(D)

WhereDistheworkpiecediameterinmm.

4.5.2Feed

Itisthedistancetraversedbythetoolalongthebed,duringonerevolutionofthework.Itsvalue

dependsuponthedepthofcutandsurfacefinishoftheworkdesired.

4.5.3DepthofCut

It is the movement of the tip of the cutting tool, from the surface of the work piece and

perpendicular to the latheaxis. Itsvaluedependsupon thenatureofoperation like rough turningor

finishturning.

4.6TOOLMATERIALS

Generalpurposehandcuttingtoolsareusuallymadefromcarbonsteelortoolsteel.Thesingle

point lathecuttingtoolsaremadeofhighspeedsteel(HSS).themainalloying elements in1841HSS


45/5142

toolsare18percent tungsten,4percentchromiumand1percentvanadium.5 to10percentcobalt is

alsoaddedtoimprovetheheatresistingpropertiesofthetool.

Carbidetippedtoolsfixedintoolholders,aremostlyusedinproductionshops.

4.7TOOLGEOMETRY

Asinglepointcuttingtoolusedonlathemaybeconsideredasasimplewedge.Figure4.8shows

thecommonturningtoolsusedfordifferentoperations.Figure6.9showsthebasicanglesofasimple

turningtool.

Figure4.8:Commonturningtools Figure4.9:Toolgeometry

4.8LATHEOPERATIONS

4.8.1Turning

Cylindricalshapes,bothexternalandinternal,areproducedbyturningoperation.Turningisthe

processinwhichthematerialisremovedbyatraversingcuttingtool,fromthesurfaceofarotatingwork

piece.Theoperationusedformachininginternalsurfacesisoftencalledtheboringoperationinwhichaholepreviouslydrilledisenlarged.

Forturninglongwork,firstitshouldbefacedandcenterdrilledatoneendandthensupported

bymeansofthetailstockcentre.

4.8.2Boring

Boring isenlargingaholeandisusedwhencorrectsizedrill isnotavailable.However,itshould

benotedthatboringcannotmakeahole.

4.8.3Facing

Facing isamachiningoperation,performedtomaketheendsurfaceoftheworkpiece,flatand

perpendiculartotheaxisofrotation.Forthis,theworkpiecemaybeheldinachuckandrotatedabout

the lathe axis.A facing tool is fedperpendicular to the axisof the lathe.The tool is slightly inclinedtowardstheendoftheworkpiece.

4.8.4TaperTurning

A taper isdefinedas theuniformchange in thediameterofaworkpiece,measuredalong its

length. It is expressed asa ratioof thedifference indiameters to the length. It is alsoexpressed in

degreesofhalftheincluded(taper)angle.

Taperturningreferstotheproductionofaconicalsurface,ontheworkpieceonalathe.

Shortsteeptapersmaybecutona lathebyswivelingthecompoundresttotherequiredangle.Here,thecuttingtoolisfedbymeansofthecompoundslidefeedhandle.Theworkpieceisrotatedinachuck

orfaceplateorbetweencenters.


46/5143

4.8.5Drilling

Holesthatareaxiallylocatedincylindricalpartsareproducedbydrillingoperation,usingatwist

drill.For this, theworkpiece is rotated inachuckor faceplate.The tailstockspindlehasastandard

taper.Thedrillbitisfittedintothetailstockspindledirectlyorthroughdrillchuck.Thetailstockisthen

movedoverthebedandclampedonitnearthework.Whenthejobrotates,thedrillbitisfedintothe

workbyturningthetailstockhandwheel.

4.8.6

Knurling

Itistheprocessofembossingadiamondshapedregularpatternonthesurfaceofaworkpiece

usingaspecialknurling tool.This toolconsistsofa setofhardened steel rollers inaholderwith the

teethcutontheirsurfaceinadefinitepattern.Thetoolisheldrigidlyonthetoolpostandtherollersare

pressedagainsttherevolvingworkpiecetosqueezethemetalagainstthemultiplecuttingedges.The

purposeofknurlingistoprovideaneffectivegrippingsurfaceonaworkpiecetopreventitfromslipping

whenoperatedbyhand.

4.8.7Chamfering

Itistheoperationofbevelingtheextremeendofaworkpiece.Chamfer isprovidedforbetter

look,toenablenuttopassfreelyonthreadedworkpiece,toremoveburrsandprotecttheendofthe

workpiecefrombeingdamaged.

4.8.8Threading

Threading isnothingbutcuttinghelicalgrooveonaworkpiece.Threadsmaybecuteitheron

the internalor external cylindrical surfaces.A specially shaped cutting tool, knownas thread cutting

tool,isusedforthispurpose.Threadcutting ina latheisperformedbytraversingthecuttingtoolata

definiterate,inproportiontotherateatwhichtheworkrevolves.

Figure4.10:OperationsofLathe


47/5144

4.9SAFETYPRECAUTIONS

1. Alwaysweareyeprotection preferablyindustrialqualitysafetyglasseswithsideshields.Thelathe

canthrowoffsharp,hotmetalchipsatconsiderablespeedaswellasspinoffspiralsofmetalthat

canbequitehazardous.Don'ttakechanceswithyoureyes.

2. Wearshortsleeveshirts,loosesleevescancatchonrotatingworkandquicklypullyourhandorarm

intoharm'sway.

3. Wearshoes

preferably

leather

work

shoes

to

protect

your

feet

from

sharp

metal

chips

on

the

shopfloorandfromtoolsandchunksofmetalthatmaygetdropped.

4. Removewristwatches,necklaces,chainsandotherjewelry.Tiebacklonghairsoitcan'tgetcaught

intherotatingwork.Thinkaboutwhathappenstoyourfaceifyourhairgetsentangled.

5. Alwaysdoublechecktomakesureyourwork issecurelyclamped inthechuckorbetweencenters

beforestartingthelathe.Startthelatheatlowspeedandincreasethespeedgradually.

6. Get in thehabitof removing thechuckkey immediatelyafteruse.Someusers recommendnever

removing yourhand from the chuck keywhen it is in the chuck. The chuck key can be a lethal

projectileifthelatheisstartedwiththechuckkeyinthechuck.

7. Keepyourfingersclearoftherotatingworkandcuttingtools.Thissoundsobvious,butIamoften

temptedtobreakawaymetalspiralsastheyformatthecuttingtool.

8. Avoidreachingoverthespinningchuck.Forfilingoperations,holdthetangendofthefile inyour

lefthand

so

that

your

hand

and

arm

are

not

above

the

spinning

chuck.

9. Neveruseafilewithabaretang thetangcouldbeforcedbackintoyourwristorpalm.


48/5145

ME101WorkshopPracticeI Machineshop

Exercise1Facingandplainturning

Aim

Toobtainrequireddiameterofacylindricalworkpiecewiththegivenlength(Fig4.11).Tools&Equipment

Lathemachine.Mildsteelbar,righthandcuttingtool,boxkeyor toolpostkey,chuckkey,steelrule,

outsidecalipersorverniercalipers.

Sketch 2x45

28.50.2

1300.2

FigureMSE1: Plain Turning

Theory

Facingistheoperationsoffinishingtheendsofworktomakeendsflat,smoothandtorequiredlength.

Roughturningoperationisusedwhereexcessivestockistoberemovedandsurfacefinishisnotcritical.

Forsuchaoperationdeepcutswithcoarsefeedareused.Duringroughmachining,maximummetal is

removedand

very

little

oversize

dimension

isleft

for

finishing

operation.

Procedure

1. Thegivenworkpieceisheldinthe3jawchuckofthelathemachineandtightenedfirmlywithchuck

key.

2. Righthand singlepointcutting tool is taken tightened firmlywith thehelpofboxkey in the tool

post.

3. Machine isswitchedonandthetoolpost isswiveledandthecuttingpoint isadjustedsuchthat it

positionedapproximatelyforfacingoperationthenthetoolisfedintotheworkpieceandthetool

postisgiventhetransversemovementbyrotatingthehandwheelofthecrossslide.

4. Withthisfacingiscompletedandthetoolpostisswiveledandcuttingpointismadeparalleltothe

axisofworkpiece.

5. Depthofcut isgivenbycrossslidetothetoolpostandthesidehandwheel isrotatedtogivethe

longitudinalmovementforthetoolpostandjobisturnedtotherequiredlengthanddiameter.

6. Aftercompletionofthejob it is inspectedfor thedimensionsobtainedwith thehelpofsteelrule

andoutsidecaliperorverniercaliper.

Precautions

1. Workpieceshouldbeheldfirmly.

2. Inroughturningoperationdonotoverfeedthetool,asitmaydamagethecuttingpointofthetool.

3. Exerciseoverhungof tool shouldbeavoidedas it results in chatterand causes roughmachined

surface.

4. Itisimportanttoensurethatduringfacingoperationthecuttingisperformedfromcenterpointtotheouterdiameteroftheworkpiece.

Result Thejobisthusmadeaccordingtothegivendimensions.


49/5146


Exercise2Stepturning

Aim

Toobtainrequireddiameters(steps)onacylindricalworkpiecewiththegivenlengths.Tools&Equipment

Lathemachine.Mildsteelbar,righthandcuttingtool,boxkeyor toolpostkey,chuckkey,steelrule,


Theory

Step turning is the operation of creating various cylindrical cross sections on ametal blank. Rough

turningoperation isusedwhereexcessivestock istoberemovedandsurfacefinish isnotcritical.For

such a operation deep cutswith coarse feed are used. During roughmachiningmaximummetal is

removedandverylittleoversizedimensionisleftforfinishingoperation.

Sketch

2x45

2616 16 22 26

40 33 27

FigureMSE2: StepTurning

Procedure

1. The givenwork piece is held in the 3jawchuckof the lathemachine and tightened firmlywith

chuckkey.

2. Righthandsinglepointcutting tool istakentightened firmlywith thehelpofboxkey in thetool

post.

3. Machineisswitchedonandthetoolpostisswiveledandthecuttingpointisadjustedsuchthatit




axisofworkpiece.

5. Depthofcutisgivenbycrossslidetothetoolpostandthesidehandwheelisrotatedtogivethe

longitudinalmovement for the toolpostandjob is turned to the required lengthanddiameters

accordingtothesketchshowninfigure.6. Aftercompletionofthejobit is inspectedforthedimensionsobtainedwiththehelpofsteelrule


Precautions


2. In rough turningoperationdonotover feed the tool,as itmaydamage thecuttingpointof the

tool.

3. Exerciseoverhungof toolshouldbeavoidedas it results inchatterandcauses roughmachined

surface.

4. Itisimportanttoensurethatduringfacingoperationthecuttingisperformedfromcenterpointto

theouterdiameteroftheworkpiece.



50/5147


Exercise3Shoulder turning

Aim

Toobtainrequireddiametersonacylindricalworkpiecewiththegivendimensions.Tools&Equipment

Lathemachine,Mildsteelbar,righthandcuttingtool,boxkeyor toolpostkey,chuckkey,steelrule,


Sketch

Figure4.13: ShoulderTurning

Procedure

1. Thegivenworkpieceisheldinthe3jawchuckofthelathemachineandtightenedfirmlywithchuck

key.

2. Righthand singlepointcutting tool is taken tightened firmlywith thehelpofboxkey in the tool

post.3. Machine isswitchedonandthetoolpost isswiveledandthecuttingpoint isadjustedsuchthat it




axisofworkpiece.

5. Depthofcut isgivenbycrossslidetothetoolpostandthesidehandwheel isrotatedtogivethe

longitudinalmovementforthetoolpostandjobisturnedtotherequiredlengthanddiameters.

6. Aftercompletionofthejob it is inspected for thedimensionsobtainedwith thehelpofsteelrule


Precautions


2. Inroughturningoperationdonotoverfeedthetool,asitmaydamagethecuttingpointofthetool.3. Exerciseoverhungof tool shouldbeavoidedas it results in chatterand causes roughmachined

surface.

4. Itisimportanttoensurethatduringfacingoperationthecuttingisperformedfromcenterpointto

theouterdiameteroftheworkpiece.



51/51

References

WorkshopmanualbyP.Kannaiah&K.L.Narayana

www.technologystudent.com

www.wikipedia.orgwww.mewelding.com

Documents

Workshop manual for fitting,welding and machine shop