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编号：时间：2021年x月x日书山有路勤为径，学海无涯苦作舟页码：第PAGE7页共NUMPAGES7页第PAGE\*MERGEFORMAT7页共NUMPAGES\*MERGEFORMAT7页Machining:AnIntroductionIntermsofannualdollarsspent,machiningisthemostimportantofthemanufacturingprocesses.Machiningcanbedefinedastheprocessofremovingmaterialfromaworkpieceintheformofchips.Thetermmetalcuttingisusedwhenthematerialismetallic.Mostmachininghasverylowset-upcostcomparedtoforming,molding,andcastingprocesses.However,machiningismuchmoreexpensiveforhighvolumes.Machiningisnecessarywheretighttolerancesondimensionsandfinishesarerequired.TheMachiningsectionisdividedintothefollowingcategories:Drilling:IntroductionDrillingiseasilythemostcommonmachiningprocess.Oneestimateisthat75%ofallmetal-cuttingmaterialremovedcomesfromdrillingoperations.Drillinginvolvesthecreationofholesthatarerightcircularcylinders.Thisisaccomplishedmosttypicallybyusingatwistdrill,somethingmostreaderswillhaveseenbefore.Thefigurebelowillustratesacrosssectionofaholebeingcutbyacommontwistdrill:Thechipsmustexitthroughtheflutestotheoutsideofthetool.Ascanbeseeninthefigure,thecuttingfrontisembeddedwithintheworkpiece,makingcoolingdifficult.Thecuttingareacanbeflooded,coolantspraymistcanbeapplied,orcoolantcanbedeliveredthroughthedrillbitshaft.Foranoverviewofthechip-formationprocess,seetheHYPERLINK"http://www.efunda.com/processes/machining/chip.cfm"ChipFormationSection.DrillingCharacteristicsThecharacteristicsofdrillingthatsetitapartfromotherpoweredmetalcuttingoperationsare:Thechipsmustexitoutoftheholecreatedbythecutting.Chipexitcancauseproblemswhenchipsarelargeand/orcontinuous.Fordeepholesinlargeworkpieces,coolantmayneedtobedeliveredthroughthedrillshafttothecuttingfront.Ofthepoweredmetalcuttingprocesses,drillingonadrillpressisthemostlikelytobeperformedbysomeonewhoisnotamachinist.DrillPressWorkAreaAviewofthemetal-cuttingareaofadrillpressisshownbelow.Theworkpieceisheldinplacebyaclampsincecuttingforcescanbequitelarge.Itisdangeroustoholdaworkpiecebyhandduringdrillingsincecuttingfo
