第0頁共35頁TCNO9524JOELBHUDSON,DENNISJREIMERWASHINGTON,DC,29OCTOBER1996ATTNATCLAO,801LEEAVENUE,FORTLEE,VIRGINIA238011713FUNDAMENTALSOFMACHINETOOLSCHAPTER4DRILLINGMACHINESGENERALINFORMATIONPURPOSETHISCHAPTERCONTAINSBASICINFORMATIONPERTAININGTODRILLINGMACHINESADRILLINGMACHINECOMESINMANYSHAPESANDSIZES,FROMSMALLHANDHELDPOWERDRILLSTOBENCHMOUNTEDANDFINALLYFLOORMOUNTEDMODELSTHEYCANPERFORMOPERATIONSOTHERTHANDRILLING,SUCHASCOUNTERSINKING,COUNTERBORING,REAMING,ANDTAPPINGLARGEORSMALLHOLESBECAUSETHEDRILLINGMACHINESCANPERFORMALLOFTHESEOPERATIONS,THISCHAPTERWILLALSOCOVERTHETYPESOFDRILLBITS,TOOK,ANDSHOPFORMULASFORSETTINGUPEACHOPERATIONSAFETYPLAYSACRITICALPARTINANYOPERATIONINVOLVINGPOWEREQUIPMENTTHISCHAPTERWILLCOVERPROCEDURESFORSERVICING,MAINTAINING,ANDSETTINGUPTHEWORK,PROPERMETHODSOFSELECTINGTOOLS,ANDWORKHOLDINGDEVICESTOGETTHEJOBDONESAFELYWITHOUTCAUSINGDAMAGETOTHEEQUIPMENT,YOURSELF,ORSOMEONENEARBYUSESADRILLINGMACHINE,CALLEDADRILLPRESS,ISUSEDTOCUTHOLESINTOORTHROUGHMETAL,WOOD,OROTHERMATERIALSFIGURE41DRILLINGMACHINESUSEADRILLINGTOOLTHATHASCUTTINGEDGESATITSPOINTTHISCUTTINGTOOLISHELDINTHEDRILLPRESSBYACHUCKORMORSETAPERANDISROTATEDANDFEDINTOTHEWORKATVARIABLESPEEDSDRILLINGMACHINESMAYBEUSEDTOPERFORMOTHEROPERATIONSTHEYCANPERFORMCOUNTERSINKING,BORING,COUNTERBORING,SPOTFACING,REAMING,ANDTAPPINGFIGURE42DRILLPRESSOPERATORSMUSTKNOWHOWTOSETUPTHEWORK,SETSPEEDANDFEED,ANDPROVIDEFORCOOLANTTOGETANACCEPTABLEFINISHEDPRODUCTTHESIZEORCAPACITYOFTHE第1頁共35頁DRILLINGMACHINEISUSUALLYDETERMINEDBYTHELARGESTPIECEOFSTOCKTHATCANBECENTERDRILLEDFIGURE43FORINSTANCE,A15INCHDRILLINGMACHINECANCENTERDRILLA30INCHDIAMETERPIECEOFSTOCKOTHERWAYSTODETERMINETHESIZEOFTHEDRILLPRESSAREBYTHELARGESTHOLETHATCANBEDRILLED,THEDISTANCEBETWEENTHESPINDLEANDCOLUMN,ANDTHEVERTICALDISTANCEBETWEENTHEWORKTABLEANDSPINDLE第2頁共35頁CHARACTERISTICSALLDRILLINGMACHINESHAVETHEFOLLOWINGCONSTRUCTIONCHARACTERISTICSFIGURE44ASPINDLESLEEVEORQUILLCOLUMN,HEAD,WORKTABLE,ANDBASETHESPINDLEHOLDSTHEDRILLORCUTTINGTOOLSANDREVOLVESINAFIXEDPOSITIONINASLEEVEINMOSTDRILLINGMACHINES,THESPINDLEISVERTICALANDTHEWORKISSUPPORTEDONAHORIZONTALTABLETHESLEEVEORQUILLASSEMBLYDOESNOTREVOLVEBUTMAYSLIDEINITSBEARINGINADIRECTIONPARALLELTOITSAXISWHENTHESLEEVECARRYINGTHESPINDLEWITHACUTTINGTOOLISLOWERED,THECUTTINGTOOLISFEDINTOTHEWORKANDWHENITISMOVEDUPWARD,THECUTTINGTOOLISWITHDRAWNFROMTHEWORKFEEDPRESSUREAPPLIEDTOTHESLEEVEBYHANDORPOWERCAUSESTHEREVOLVINGDRILLTOCUTITSWAYINTOTHEWORKAFEWTHOUSANDTHSOFANINCHPERREVOLUTION第3頁共35頁THECOLUMNOFMOSTDRILLPRESSESISCIRCULARANDBUILTRUGGEDANDSOLIDTHECOLUMNSUPPORTSTHEHEADANDTHESLEEVEORQUILLASSEMBLYTHEHEADOFTHEDRILLPRESSISCOMPOSEDOFTHESLEEVE,SPINDLE,ELECTRICMOTOR,ANDFEEDMECHANISMTHEHEADISBOLTEDTOTHECOLUMNTHEWORKTABLEISSUPPORTEDONANARMMOUNTEDTOTHECOLUMNTHEWORKTABLECANBEADJUSTEDVERTICALLYTOACCOMMODATEDIFFERENTHEIGHTSOFWORKORITMAYBESWUNGCOMPLETELYOUTOFTHEWAYITMAYBETILTEDUPTO90INEITHERDIRECTION,TOALLOWFORLONGPIECESTOBEENDORANGLEDDRILLEDTHEBASEOFTHEDRILLINGMACHINESUPPORTSTHEENTIREMACHINEANDWHENBOLTEDTOTHEFLOOR,PROVIDESFORVIBRATIONFREEOPERATIONANDBESTMACHININGACCURACYTHETOPOFTHEBASEISSIMILARTOAWORKTABLEANDMAYBEEQUIPPEDWITHTSLOTSFORMOUNTINGWORKTOOLARGEFORTHETABLECAREOFDRILLINGMACHINESLUBRICATIONLUBRICATIONISIMPORTANTBECAUSEOFTHEHEATANDFRICTIONGENERATEDBYTHEMOVINGPARTSFOLLOWTHEMANUFACTURERSMANUALFORPROPERLUBRICATIONMETHODSCLEANEACHMACHINEAFTERUSECLEANTSLOTSGROOVESANDDIRTFROMBELTSANDPULLEYSREMOVECHIPSTOAVOIDDAMAGETOMOVINGPARTSWIPEALLSPINDLESANDSLEEVESFREEOFGRITTOAVOIDDAMAGINGTHEPRECISIONFITPUTALIGHTCOATOFOILONALLUNPAINTEDSURFACESTOPREVENTRUSTOPERATEALLMACHINESWITHCARETOAVOIDOVERWORKINGTHEELECTRICMOTORSPECIALCAREOPERATIONSUNDERADVERSECONDITIONSREQUIRESPECIALCAREIFMACHINESAREOPERATEDUNDEREXTREMELYDUSTYCONDITIONSOPERATEATTHESLOWESTSPEEDSTOAVOIDRAPIDABRASIVEWEARONTHEMOVINGPARTSANDLUBRICATETHEMACHINESMOREOFTENUNDEREXTREMECOLDCONDITIONS,STARTTHEMACHINESATASLOWSPEEDANDALLOWTHEPARTSANDLUBRICANTSTOWARMUPBEFOREINCREASINGTHESPEEDSMETALBECOMESVERYBRITTLEINEXTREMECOLDSODONOTSTRIKETHEMACHINESWITHHARDTOOLSEXTREMEHEATMAYCAUSETHEMOTORTOOVERHEATSOUSEINTERMITTENTORONANDOFF,OPERATIONSTOKEEPTHEMOTORRUNNINGCOOLTYPESOFDRILLINGMACHINESTHEREARETWOTYPESOFDRILLINGMACHINESUSEDBYMAINTENANCEPERSONNELFORREPAIRINGANDFABRICATINGNEEDEDPARTSHANDFEEDORPOWERFEEDOTHERTYPESOF第4頁共35頁DRILLINGMACHINES,SUCHASTHERADIALDRILLPRESSNUMERICALLYCONTROLLEDDRILLINGMACHINEMULTIPLESPINDLEDRILLINGMACHINE,GANGDRILLINGMACHINE,ANDTURRETDRILLPRESS,AREALLVARIATIONSOFTHEBASICHANDANDPOWERFEEDDRILLINGMACHINESTHEYAREDESIGNEDFORHIGHSPEEDPRODUCTIONANDINDUSTRIALSHOPSDRILLINGDEPTHISCONTROLLEDBYADEPTHSTOPMECHANISMLOCATEDONTHESIDEOFTHESPINDLETHEOPERATOROFTHEMACHINEMUSTUSEASENSEOFFEELWHILEFEEDINGTHECUTTINGTOOLINTOTHEWORKTHEOPERATORMUSTPAYATTENTIONANDBEALERTTOWHENTHEDRILLBREAKSTHROUGHTHEWORK,BECAUSEOFTHETENDENCYOFTHEDRILLTOGRABORSNAGTHEWORKPIECE,OFTHESEMACHINES,OPERATIONSTHATREQUIREDRILLINGSPEEDSLESSTHAN450REVOLUTIONSPERMINUTECANNOTBEPERFORMEDREAMING,COUNTERBORING,ANDCOUNTERSINKINGMAYREQUIRESLOWERSPEEDSTHANDRILLINGANDMAYNOTBEABLETOBEPERFORMEDFORALLMATERIALSONTHESEMACHINESHANDFEEDTHEHANDFEEDDRILLINGMACHINESFIGURE45ARETHESIMPLESTANDMOSTCOMMONTYPEOFDRILLINGMACHINESINUSETODAYTHESEARELIGHTDUTYMACHINESTHATAREHANDFEDBYTHEOPERATOR,USINGAFEEDHANDLESOTHATTHEOPERATORISABLETO“FEEL”THEACTIONOFTHECUTTINGTOOLASITCUTSTHROUGHTHEWORKPIECETHESEDRILLINGMACHINESCANBEBENCHORFLOORMOUNTEDTHEYAREDRIVENBYANELECTRICMOTORTHATTURNSADRIVEBELTONAMOTORPULLEYTHATCONNECTSTOTHESPINDLEPULLEYHANDFEEDMACHINESAREESSENTIALLYHIGHSPEEDMACHINESANDAREUSEDONSMALLWORKPLACESTHATREQUIREHOLES1/2INCHORSMALLERNORMALLY,THEHEADCANBEMOVEDUPANDDOWNONTHECOLUMNBYLOOSENINGTHELOCKINGBOLTSWHICHALLOWSTHEDRILLINGMACHINETODRILLDIFFERENTHEIGHTSOFWORKPOWERFEEDTHEPOWERFEEDDRILLINGMACHINESFIGURE46AREUSUALLYLARGERANDHEAVIERTHANTHEHANDFEEDTHEYAREEQUIPPEDWITHTHEABILITYTOFEEDTHECUTTINGTOOLINTOTHEWORKAUTOMATICALLY,ATAPRESETDEPTHOFCUTPERREVOLUTIONOFTHESPINDLE,USUALLYINTHOUSANDTHSOFANINCHPERREVOLUTIONTHESEMACHINESAREUSEDINMAINTENANCESHOPSFORMEDIUMDUTYWORK,ORWORKTHATUSESLARGEDRILLSTHATREQUIREPOWERFEEDSTHEPOWERFEEDCAPABILITYISNEEDEDFORDRILLSORCUTTINGTOOKTHATAREOVER1/2INCHINDIAMETER,BECAUSETHEYREQUIREMOREFORCETOCUTTHANTHATWHICHCANBEPROVIDEDBYUSINGHANDPRESSURETHESPEEDSAVAILABLEONPOWERFEEDMACHINESCANVARYFROMABOUT50RPMTOABOUT1,800RPMTHESLOWERSPEEDSALLOWFORSPECIALOPERATIONS,SUCHASCOUNTERBORING,COUNTERSINKING,ANDREAMING第5頁共35頁THESIZESOFTHESEMACHINESGENERALLYRANGEFROM17INCHTOA22INCHCENTERDRILLINGCAPACITY,ANDAREUSUALLYFLOORMOUNTEDTHEYCANHANDLEDRILLSUPTO2INCHESINDIAMETER,WHICHMOUNTINTOTAPEREDMORSESOCKETSLARGERWORKPLACESAREUSUALLYCLAMPEDDIRECTLYTOTHETABLEORBASEUSINGTBOLTSANDCLAMPS,WHILESMALLWORKPLACESAREHELDINAVISEADEPTHSTOPMECHANISMISLOCATEDONTHEHEAD,NEARTHESPINDLE,TOAIDINDRILLINGTOAPRECISEDEPTHSAFETYPRECAUTIONSDRILLINGMACHINESAFETYDRILLINGMACHINESAREONEOFTHEMOSTDANGEROUSHANDOPERATEDPIECESOFEQUIPMENTINTHESHOPAREAFOLLOWINGSAFETYPROCEDURESDURINGDRILLINGOPERATIONSWILLHELPELIMINATEACCIDENTS,LOSSOFTIME,ANDMATERIALSLISTEDBELOWKEEPALLLOOSECLOTHINGAWAYFROMTURNINGTOOLSARESAFETYPROCEDURESCOMMONTOMOSTTYPESOFDRILLINGACHINESFOUNDINTHEMACHINESHOPMAKESURETHATTHECUTTINGTOOLSARERUNNINGSTRAIGHTBEFORESTARTINGTHEOPERATIONDONOTSUPPORTTHEWORKPLACESBYHANDNEVERMAKEANYADJUSTMENTSWHILETHEMACHINEISOPERATINGNEVERCLEANAWAYCHIPSWITHYOURHANDUSEABRUSHNEVERPLACETOOLSOREQUIPMENTONTHEDRILLINGTABLESKEEPALLGUARDSINPLACEWHILEOPERATINGEASEUPONTHEFEEDASTHEDRILLBREAKSTHROUGHTHEWORKTOAVOIDDAMAGEDTOOLSORWORKPLACES第6頁共35頁REMOVEALLCHUCKKEYSANDWRENCHESBEFOREOPERATINGALWAYSWEAREYEPROTECTIONWHILEOPERATINGANYDRILLINGMACHINESTOOLSANDEQUIPMENTTWISTDRILLSTWISTDRILLSARETHEMOSTCOMMONCUTTINGTOOLSUSEDWITHDRILLINGMACHINESTWISTDRILLSAREDESIGNEDTOMAKEROUNDHOLESQUICKLYANDACCURATELYINALLMATERIALSTHEYARECALLEDTWISTDRILLSMAINLYBECAUSEOFTHEHELICALFLUTESORGROOVESTHATWINDAROUNDTHEBODYFROMTHEPOINTTOTHENECKOFTHEDRILLANDAPPEARTOBETWISTEDFIGURE47TWISTDRILLSARESIMPLYCONSTRUCTEDBUTDESIGNEDVERYTOUGHTOWITHSTANDTHEHIGHTORQUEOFTURNING,THEDOWNWARDPRESSUREONTHEDRILL,ANDTHEHIGHHEATGENERATEDBYFRICTIONTHEREARETWOCOMMONTYPESOFTWISTDRILLS,HIGHSPEEDSTEELDRILLS,ANDCARBIDETIPPEDDRILLSTHEMOSTCOMMONTYPEUSEDFORFIELDANDMAINTENANCESHOPWORKISTHEHIGHSPEEDSTEELTWISTDRILLBECAUSEOFITSLOWCOSTCARBIDETIPPEDMETALDRILLSAREUSEDINPRODUCTIONWORKWHERETHEDRILLMUSTREMAINSHARPFOREXTENDEDPERIODS,SUCHASINANUMERICALLYCONTROLLEDDRILLINGMACHINEOTHERTYPESOFDRILLSAVAILABLEARECARBIDETIPPEDMASONRYDRILLS,SOLIDCARBIDEDRILLS,TINCOATEDDRILLS,PARABOLICDRILLSANDSPLITPOINTDRILLSTWISTDRILLSARECLASSIFIEDASSTRAIGHTSHANKORTAPEREDSHANKFIGURE47STRAIGHTSHANKTWISTDRILLSAREUSUALLYL/2INCHORSMALLERANDTITINTOGEAREDDRILLCHUCKS,WHILETAPEREDSHANKDRILLSAREUSUALLYFORTHELARGERDRILLSTHAT第7頁共35頁NEEDMORESTRENGTHWHICHISPROVIDEDBYTHETAPERSOCKETCHUCKSCOMMONTWISTDRILLSIZESRANGEFROM00135WIREGAGESIZENO80TO3500INCHESINDIAMETERLARGERHOLESARECUTBYSPECIALDRILLSTHATARENOTCONSIDEREDASTWISTDRILLSTHESTANDARDSIZESUSEDINTHEUNITEDSTATESARETHEWIREGAGENUMBEREDDRILLS,LETTERDRILLS,FRACTIONALDRILLS,ANDMETRICDRILLSSEETABLE41,INAPPENDIXATWISTDRILLSCANALSOBECLASSIFIEDBYTHEDIAMETERANDLENGTHOFTHESHANKANDBYTHELENGTHOFTHEFLUTEDPORTIONOFTHETWISTDRILLWIREGAGETWISTDRILLSANDLETTERTWISTDRILLSAREGENERALLYUSEDWHEREOTHERTHANSTANDARDFRACTIONALSIZESAREREQUIRED,SUCHASDRILLINGHOLESFORTAPPINGINTHISCASE,THEDRILLEDHOLEFORMSTHEMINORDIAMETEROFTHETHREADTOBECUT,ANDTHEMAJORDIAMETERWHICHISCUTBYTAPPINGCORRESPONDSTOTHECOMMONFRACTIONALSIZEOFTHESCREWWIREGAGETWISTDRILLSRANGEFROMTHESMALLESTTOTHELARGESTSIZEFROMNO8000135INCHTONO102280INCHTHELARGERTHENUMBER,THESMALLERTHEDIAMETEROFTHEDRILLLETTERSIZETWISTSDRILLSRANGEFROMA0234INCHTOZ0413INCHASTHELETTERSPROGRESS,THEDIAMETERSBECOMELARGERFRACTIONALDRILLSRANGEFROM1/64TO13/4INCHESINL/64INCHUNITSFROM1/32TO21/4INCHESIN1/32INCHUNITS,ANDFROM1/16TO31/2INCHESIN1/16INCHUNITSMETRICTWISTDRILLSARERANGEDINTHREEWAYSMINIATURESET,STRAIGHTSHANK,ANDTAPERSHANKMINIATUREMETRICDRILLSETSRANGEFROM004MMTO099MMINUNITSOF001MMSTRAIGHTSHANKMETRICDRILLSRANGEFROM005MMTO200MMINUNITSFROM002MMTO005MMDEPENDINGONTHESIZEOFTHEDRILLTAPERSHANKDRILLSRANGEINSIZEFROM8MMTO80MMINUNITSFROM001MMTO005MMDEPENDINGONTHESIZEOFTHEDRILLTHEDRILLGAGEFIGURE48ISUSEDTOCHECKTHEDIAMETERSIZEOFATWISTDRILLTHEGAGECONSISTSOFAPLATEHAVINGASERIESOFHOLESTHESEHOLESCANBENUMBERED,LETTERED,FRACTIONAL,ORMETRICSIZEDTWISTDRILLSTHECUTTINGENDOFTHEDRILLISPLACEDINTOTHEHOLETOCHECKTHESIZEAMICROMETERCANALSOBEUSEDTOCHECKTHESIZEOFATWISTDRILLBYMEASURINGOVERTHEMARGINSOFTHEDRILLFIGURE49THESMALLERSIZESOFDRILLSARENOTUSUALLYMARKEDWITHTHEDRILLSIZEORWORNDRILLSMAYHAVETHEDRILLSIZERUBBEDOFF,THUSADRILLGAGEORMICROMETERMUSTBEUSEDTOCHECKTHESIZEITISIMPORTANTTOKNOWTHEPARTSOFTHETWISTDRILLFORPROPERIDENTIFICATIONANDSHARPENINGFIGURE47THEPOINTISTHEENTIRECONICALSHAPEDENDOFTHEDRILLCONTAININGTHECUTTINGEDGES第8頁共35頁ANDCHISELEDGETHEBODYISTHEPARTOFTHEDRILLTHATISFLUTEDANDRELIEVEDTHESHANKISTHEPARTTHATFITSINTOTHEHOLDINGDEVICE,WHETHERITISASTRAIGHTSHANKORATAPEREDSHANKTHECHISELEDGEISTHEPOINTATWHICHTHETWOLIPSMEETTHE第9頁共35頁CHISELEDGEACTSASACHISELWHENTHEDRILLISTURNINGANDCUTSINTOTHEWORKPIECETHECHISELEDGEMUSTALWAYSBECENTEREDEXACTLYONTHEDRILLSAXISFORACCURATECUTTINGACTIONTHECUTTINGEDGELIPSCUTLIKEKNIVESWHENFEDANDROTATEDINTOTHEWORKPIECETHELIPSARESHARPEDGESFORMEDBYGRINDINGTHEFLUTESTOACONICALPOINTTHEHEELISTHECONICALSHAPEDPORTIONOFTHEPOINTINBACKOFTHECUTTINGEDGELIPSTHEAMOUNTOFSLOPEGIVENTOTHEHEELINBACKOFTHEDRILLLIPSISCALLEDLIPCLEARANCETHISCLEARANCEISNECESSARYTOKEEPTHEHEELFROMRUBBINGTHEBOTTOMOFTHEHOLEBEINGDRILLEDRUBBINGWOULDPREVENTTHEDRILLFROMCUTTINGTHEFLUTEISTHEHELICALGROOVEONTHEDRILLITCARRIESOUTTHECHIPSANDADMITSCOOLANTTOTHECUTTINGEDGESTHEMARGINISTHENARROWSURFACEALONGTHEFLUTESTHATDETERMINESTHESIZEOFTHEDRILLANDKEEPSTHEDRILLALIGNEDTHEPORTIONOFTHEDRILLBODYTHATISRELIEVEDBEHINDTHEMARGINISKNOWNASTHEBODYCLEARANCETHEDIAMETEROFTHISPARTISLESSTHANTHATOFTHEMARGINANDPROVIDESCLEARANCESOTHATALLOFTHEBODYDOESNOTRUBAGAINSTTHESIDEOFTHEHOLEANDCAUSEFRICTIONTHEBODYCLEARANCEALSOPERMITSPASSAGEOFLUBRICANTSAROUNDTHEDRILLTHENARROWEDENDOFTHETAPEREDSHANKDRILLISCALLEDTHETANGTHETANGFITSTHESLOTINTHEINNERMOSTENDOFTHEDRILLSPINDLE,DRILLCHUCK,OROTHERDRILLHOLDINGDEVICEANDAIDSINDRIVINGTHETOOLITALSOPREVENTSTHEDRILLFROMSLIPPINGTHEWEBOFTHEDRILLISTHEMETALSECTIONSEPARATINGTHEFLUTESITRUNSTHELENGTHOFTHEBODYBETWEENTHEFLUTESTHEWEBGRADUALLYINCREASESINTHICKNESSTOWARDTHESHANK,INCREASINGTHERIGIDITYOFTHEDRILLANIMAGINARYLINETHROUGHTHECENTEROFTHEDRILLFROMENDTOENDISTHEAXISTHEDRILLMUSTROTATEEVENLYABOUTTHEAXISATALLTIMESSPECIALDRILLSSPECIALDRILLSARENEEDEDFORSOMEAPPLICATIONSTHATANORMALHIGHSPEEDINDUSTRIALOPERATIONSOTHERTYPESOFSPECIALDRILLSGENERALPURPOSEDRILLCANNOTACCOMPLISHQUICKLYORACCURATELYARELEFTHANDDRILL,SILVERANDDEMING,SPOTTING,SLOWSPIRAL,SPECIALDRILLSCANBETWISTDRILLTYPE,STRAIGHTFLUTEDTYPE,ORFASTSPIRAL,HALFROUND,DIE,FLAT,ANDCOREDRILLSTHEGENERALSPECIALFLUTEDSPECIALDRILLSCANBEKNOWNBYTHEJOBTHATTHEYPURPOSEHIGHSPEEDDRILL,WHICHISTHECOMMONTWISTDRILLUSEDAREDESIGNEDFOR,SUCHASAIRCRAFTLENGTHDRILLS,WHICHHAVEANFORMOSTFIELDANDMAINTENANCESHOPS,CANBEREGROUNDANDEXTENDEDSHANKSPECIALDRILLSAREUSUALLY第10頁共35頁USEDINADAPTEDFORMOSTSPECIALDRILLINGNEEDSSHARPENINGTWISTDRILLSTWISTDRILLSBECOMEDULLANDMUSTBERESHARPENEDTHEPREFERREDMETHODOFRESHARPENINGATWISTDRILLISWITHTHEDRILLGRINDINGMACHINE,BUTTHISMACHINEISNOTALWAYSAVAILABLEINFIELDANDMAINTENANCEUNITS,SOTHEOFFHANDMETHODOFDRILLSHARPENINGMUSTBEUSEDFIGURE410THEOFFHANDMETHODREQUIRESTHATTHEOPERATORHAVEAKNOWLEDGEOFTHEDRILLINGGEOMETRYFIGURE411ANDHOWTOCHANGEDRILLANGLESASNEEDEDFORANYDRILLINGJOBSEETABLE42INAPPENDIXATOOLSNEEDEDAREAUTILITYORBENCHGRINDERWITHADRESSEDWHEELANDADRILLPOINTGAGEFIGURE412ORPROTRACTORHEADONTHECOMBINATIONSQUARETHEDRILLPOINTGAGEISSETAT59ANDADJUSTEDALONGTHESTEELRULETOFITTHEDRILLTOBESHARPENEDTHECUTTINGLIPSMUSTBEOFTHESAMEANGLE,THELIPCLEARANCEANGLEMUSTBEWITHINASPECIFICDEGREERANGE,ANDTHECUTTINGLIPSMUSTBEOFANEQUALLENGTHTHEREARESEVERALBASICCHARACTERISTICSTHATALLTWISTDRILLSMUSTHAVETOCUTPROPERLYTHEFOLLOWINGWILLCOVERTHOSECHARACTERISTICS第11頁共35頁PRECHECKBEFORESHARPENINGATWISTDRILL,THEOPERATORMUSTCHECKTHECONDITIONOFTHEDRILLFORCHIPPEDANDCRACKEDLIPSOREDGESTHATMUSTBEGROUNDOFFDURINGTHESHARPENINGPROCESSTHEOPERATORMUSTALSOCHECKTHEREFERENCESFORTHEPROPERLIPANGLEANDLIPCLEARANCEANGLEFORTHEMATERIALTOBEDRILLEDAFTERSETTINGUPTHEBENCHGRINDERFOROFFHANDDRILLSHARPENING,THEOPERATORASSUMESACOMFORTABLESTANCEINFRONTOFTHEGRINDINGWHEELTOSHARPENTHETWISTDRILLTHESUGGESTEDMETHODISTOGRINDTHELIPANGLEFIRST,THENCONCENTRATEONGRINDINGTHELIPCLEARANCEANGLE,WHICHWILLTHENDETERMINETHELIPLENGTHTHEUSUALLIPANGLEISANINCLUDEDANGLEOF11859X2FIGURE413,WHICHISTHELIPANGLEOFGENERALPURPOSEDRILLSUSETHEDRILLPOINTGAGEFREQUENTLYTOCHECKLIPANGLEANDLIPLENGTHWHENGRINDING,DONOTALLOWTHEDRILLTOBECOMEOVERHEATEDOVERHEATINGWILLCAUSETHEDRILLEDGESTOBECOMEBLUEWHICHISANINDICATIONTHATTHEDRILLSTEMPERHASBEENLOSTTHEBLUEAREAMUSTBEGROUNDCOMPLETELYAWAYTOREESTABLISHTHEDRILLSTEMPERIFADRILLBECOMESTOOHOTDURINGSHARPENING,THELIPSCANCRACKWHENDIPPEDINTOCOLDWATERORCOOLANT第12頁共35頁DRILLPOINTWHENGRINDINGTHELIPANGLE,USETHEDRILLPOINTGAGEANDGRINDONELIPPERFECTLYSTRAIGHTANDATTHEREQUIREDANGLEUSUALLY590THENFLIPTHEDRILLOVERANDGRINDTHEOTHERLIPONCETHEANGLEISESTABLISHED,THENTHELIPCLEARANCEANGLEANDLIPLENGTHCANBEGROUNDIFBOTHLIPSARENOTSTRAIGHTANDOFTHESAMEANGLE,THENTHECHISELEDGEFIGURE414WILLNOTBEESTABLISHEDITISITIMPORTANTTOHAVEASHARPANDCENTEREDCHISELEDGEORTHEDRILLWILLNOTROTATEEXACTLYONITSCENTERANDTHEHOLEWILLBEOVERSIZEDIFTHEDRILLPOINTISTOOSTEEP,THEDRILLWILLREQUIREMOREPOWERANDCUTSLOWLYWHENTHEANGLESOFTHECUTTINGLIPSAREDIFFERENT,THENTHEDRILLWILLONLYHAVEONELIPCUTTINGASITREVOLVESTHEHOLEWILLBEOVERSIZEDANDTHEDRILLWILLWEARVERYRAPIDLYWHENBOTHTHEANGLESANDTHELENGTHOFTHEANGLESAREINCORRECT,THENEXCESSIVEWEARISPUTONBOTHTHEDRILLANDMACHINE,WHICHWILLRESULTINPOORWORKMANSHIPFIGURE415第13頁共35頁CLEARANCEANGLEWHENGRINDINGTHELIPCLEARANCEANGLE,FIGURE413,RELIEFMUSTBEGIVENTOBOTHCUTTINGEDGESALLOWINGTHEMTOENTERINTOTHEWORKPIECETODOTHECUTTINGGENERALPURPOSEDRILLSHAVEACLEARANCEOF8TO12THECHISELEDGEOFACORRECTLYGROUNDDRILLSHOULDBEATANANGLEOFABOUT45WITHTHELINEOFTHECUTTINGEDGESTHEANGLEOFTHECHISELEDGETOTHELIPSISAGUIDETOTHECLEARANCEFIGURE416TOOMUCHCLEARANCEWILLCAUSETHEDRILLTOBREAKDOWNBECAUSEOFINSUFFICIENTSUPPORTOFTHELIP,ANDTHEREWILLNOTBEENOUGHLIPTHICKNESSTOCARRYAWAYTHEGENERATEDHEATTOOLITTLECLEARANCEWILLRESULTINTHEDRILLHAVINGLITTLEORNOCUTTINGEDGES,ANDTHEINCREASEDPRESSUREREQUIREDTOFEEDITINTOTHEHOLEWILLCAUSETHEDRILLTOBREAKBYLOOKINGSTRAIGHTONTOTHECUTTINGTIPOFTHEDRILL,THEOPERATORCANSEEIFTHECHISELEDGEISCORRECTIFTHECHISELEDGEISCORRECTAT45TOTHELIPS,THENITISANINDICATIONTHATTHELIPCLEARANCEANGLEISCORRECTANINCORRECTCHISELEDGEISUSUALLY第14頁共35頁PRODUCEDBYHOLDINGTHEDRILLATANINCORRECTANGLETOTHEWHEELFIGURE417WHENGRINDINGAGOODGUIDEISTOHOLDTOTHEGROUND,ANDMAKESLIGHTADJUSTMENTSRAKEANGLETHEANGLEBETWEENTHEFLUTEANDTHEAXISTHEDRILLPARALLELOFTHEDRILLTHATFORMSTHECUTTINGEDGEISKNOWNASTHERAKEANGLEFIGURE41830BEINGTHEMOSTCOMMONDRILLSUSEDONARMORPLATEOROTHERVERYHARDMATERIALSNEEDAREDUCEDRAKEANGLETOINCREASETHESUPPORTBEHINDTHECUTTINGEDGESOFTMATERIALS,LIKEBRASSANDBRONZE,ALSOUSEAREDUCEDRAKEANGLETOPREVENTTHEDRILLFROMGRABBINGTHERAKEANGLEPARTIALLYGOVERNSTHETIGHTNESSWITHWHICHTHECHIPSCURLANDTHEAMOUNTOFSPACETHEYOCCUPYIFTHERAKEANGLEISTOOSMALL,THELIPSMAYBETOOTHINANDBREAKUNDERTHESTRAINOFDRILLINGTOOLARGEOFARAKEANGLEMAKESTHEDRILLCHATTERANDVIBRATEEXCESSIVELYTHEWEBOFADRILLISMADETHICKERTOWARDTHESHANKTOSTRENGTHENTHETOOLINSMALLERSIZEDRILLS,THEDIFFERENCEISNOTNOTICEABLE,BUTINLARGERDRILLS,WHENTHEPOINTISGROUNDBACKBYREPEATEDSHARPENING,THETHICKNESSOFTHEWEBBECOMESGREATERANDTHECHISELEDGEOFTHEDRILLBECOMESWIDERTHISCAUSESTHECHISELEDGETOSCRAPEONTHEBOTTOMOFTHEHOLEANDREQUIRESEXCESSIVEPRESSURETOBEAPPLIEDTOTHEDRILLTHISCANBECORRECTEDBYTHINNINGTHEWEBFIGURE419THEPOINTISGROUNDTHINNERONATHINGRINDINGWHEELWITHAROUNDEDFACETOFITINTOTHEFLUTEANEQUALAMOUNTOFMETALSHOULDBEGROUNDFROMEACHFLUTE第15頁共35頁DRILLGRINDINGMACHINESDRILLGRINDINGMACHINESFIGURE420MAKETHEACCURATEGRINDINGOFALLTYPESANDSIZESOFDRILLSANEASYJOBCOMPARATIVELYLITTLESKILLISREQUIREDTOSHARPENDRILLSWITHTHESEMACHINESWHILEFOLLOWINGTHEOPERATINGINSTRUCTIONS第16頁共35頁THEYAREPARTICULARLYVALUABLEWHENALARGENUMBEROFTHESAMEGENERALTYPEOFDRILLSISTOBESHARPENEDTWOBASICDESIGNSFORTHEBENCHTYPEDRILLGRINDINGMACHINESAREAVAILABLEBOTHPERFORMTHESAMEOPERATIONSBUTUSEDIFFERENTDRILLHOLDINGDEVICESTHECAPACITYOFTHESEMACHINESISSTATEDINTHE