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1、剑五汽蹿辽漫晦墅蘼莼MachiningTechniquesAndTool永滞津翠暑舜懑碱弟沭DrillingandDrills瓿倒苎畈邈砖翠敖狁辨Drillinginvolvesproducingthroughorblindholesinaworkpiecebyforcingatool,whichrotatesarounditsaxis,againsttheworkpiece.日辏烬嫂殆猢鸠废舨骏Consequently,therangeofcuttingfromthataxisofrotationisequaltotheradiusoftherequiredhole.In
2、practice,twosymmetricalcuttingedgesthatrotateaboutthesameaxisareemployed.糈黠捍咔旃卉轷瞳缔瀑Drillingoperationscanbecarriedoutbyusingeitherhanddrillsordrillingmachines.Thelatterdifferinsizeandconstruction.Nevertheless,thetoolalwaysrotatesarounditsaxiswhiletheworkpieceiskeptfirmlyfixed.Thisiscontrary
3、todrillingonalathe.抗挑险解绺投假化慷辍CuttingToolforDrillingOperation描井瓷厅纣指冒铒营么Indrillingoperations,acylindricalrotary-endcuttingtool,calledadrill,isemployed.Thedrillcanhaveeitheroneormorecuttingedgesandcorrespondingflutes,whichcanbestraightorhelical.淮潮金戽馇疡岈纫绷蝣Thefunctionoftheflutesistoprovideoutle
4、tpassagesforthechipsgeneratedduringthedrillingoperationandalsotoallowlubricantsandcoolantstoreachthecuttingedgesandthesurfacebeingmachined.Followingisasurveyofthecommonlyuseddrills.奶瞽脆脉黉熠稃脞炅噎Twistdrill.Thetwistdrillisthemostcommontypeofdrill.Ithastwocuttingedgesandtwohelicalflutesthatconti
5、nueoverthelengthofthedrillbody,.Thedrillalsoconsistsofaneckandashankthatcanbeeitherstraightortapered.舵菩无螭字品蚓枵胚击Inthelattercase,theshankisfittedbythewedgeactionintothetaperedsocketofthespindleandhasatang,whichgoesintoaslotinthespindlesocket,thusactingasasolidmeansfortransmittingrotation.迤钙帽
6、陌兀瞥噬蠢蚋彩Ontheotherhand,straight-shankdrillsareheldinadrillchuckthatis,inturn,fittedintothespindlesocketinthesamewayastaperedshankdrills.穰省捱钯畅肯挚判慧绀Thetwocuttingedgesarereferredtoasthelips,andareconnectedtogetherbyawedge,whichisachisel-likeedge.Thetwistdrillalsohastwomargins,whichenableproper
7、guidanceandlocatingofthedrillwhileitisinoperation.亡本吖狰肉桥酩俳锓茎Thetoolpointangle(TPA)isformedbythetwolipsandischosenbasedonthepropertiesofthematerialtobecut.TheusualTPAforcommercialdrillsis118°,whichisappropriatefordrillinglow-carbonsteelsandcastirons.襁糟忿挥里距坷扶坠褴F
