機械工程英語10

Unit12

DrillingandMilling

第十二章鉆削與銑削

Drillinginvolvesproducingthroughorblindholesinaworkpiecebyforcingatool,whichrotatesarounditsaxis,againsttheworkpiece.

鉆削就是通過迫使繞自身軸線旋轉的切削刀具進入工件而在其上生成通孔或盲孔。Consequently,therangeofcuttingfromthataxisofrotationisequaltotheradiusoftherequiredhole.Inpractice,twosymmetricalcuttingedgesthatrotateaboutthesameaxisareemployed.因此，從旋轉軸線開始的切削范圍等于所需孔的半徑。實際上，使用的是兩條圍繞相同軸線旋轉的對稱切削刃。DrillingandDrills鉆削和鉆頭Drillingoperationscanbecarriedoutbyusingeitherhanddrillsordrillingmachines.Thelatterdifferinsizeandconstruction.Nevertheless,thetoolalwaysrotatesarounditsaxiswhiletheworkpieceiskeptfirmlyfixed.Thisiscontrarytodrillingonalathe.

鉆削作業(yè)既能采用手鉆也能采用鉆床來實現(xiàn)。鉆床在尺寸和結構上雖有差別，然而始終都是切削刀具圍繞自身軸線旋轉、工件穩(wěn)固定位的形式。這正好與在車床上鉆孔相反。CuttingToolforDrillingOperation

用于鉆削作業(yè)的切削刀具

Indrillingoperations,acylindricalrotary-endcuttingtool,calledadrill,isemployed.Thedrillcanhaveeitheroneormorecuttingedgesandcorrespondingflutes,whichcanbestraightorhelical.

在鉆削作業(yè)中，要用到被稱為鉆頭的圓柱形回轉端切削刀具。鉆頭可以有一條或多條直的或是螺旋狀的切削刃以及相應的出屑槽。Thefunctionoftheflutesistoprovideoutletpassagesforthechipsgeneratedduringthedrillingoperationandalsotoallowlubricantsandcoolantstoreachthecuttingedgesandthesurfacebeingmachined.Followingisasurveyofthecommonlyuseddrills.出屑槽的功能是給鉆削作業(yè)中產(chǎn)生的切屑提供排出通道，并允許潤滑劑和冷卻液到達切削刃和正在被加工的表面。下面是常用鉆頭的概述。Twistdrill.Thetwistdrillisthemostcommontypeofdrill.Ithastwocuttingedgesandtwohelicalflutesthatcontinueoverthelengthofthedrillbody,asshowninFig.12.1.Thedrillalsoconsistsofaneckandashankthatcanbeeitherstraightortapered.

麻花鉆：麻花鉆是最常用的鉆頭類型。它有兩條切削刃和兩條沿鉆頭體全長連續(xù)的螺旋狀出屑槽，如圖12.1所示。麻花鉆還包括鉆頸和鉆柄，鉆柄可以是直的也可以是錐形的。Inthelattercase,theshankisfittedbythewedgeactionintothetaperedsocketofthespindleandhasatang,whichgoesintoaslotinthespindlesocket,thusactingasasolidmeansfortransmittingrotation.錐形鉆柄通過楔入動作安裝在主軸的錐形軸孔中，鉆柄上還有柄舌插入主軸軸孔中的插槽，從而作為傳遞轉動的可靠方法。Ontheotherhand,straight-shankdrillsareheldinadrillchuckthatis,inturn,fittedintothespindlesocketinthesamewayastaperedshankdrills.另一方面，直柄鉆頭用鉆頭卡盤夾住，接下來鉆頭卡盤則象錐形鉆柄鉆頭一樣安裝在主軸軸孔內(nèi)。

AscanbeseeninFig.12.1,thetwocuttingedgesarereferredtoasthelips,andareconnectedtogetherbyawedge,whichisachisel-likeedge.Thetwistdrillalsohastwomargins,whichenableproperguidanceandlocatingofthedrillwhileitisinoperation.

如圖12.1所示，兩條切削刃就是鉆唇，通過鑿子狀邊緣的楔形體連在一起。麻花鉆還有兩條導向邊，用于作業(yè)中鉆頭的正確導向和定位。Thetoolpointangle(TPA)isformedbythetwolipsandischosenbasedonthepropertiesofthematerialtobecut.TheusualTPAforcommercialdrillsis118°,whichisappropriatefordrillinglow-carbonsteelsandcastirons.兩條鉆唇形成鉆頂角，并根據(jù)被鉆削材料的性能來選取其大小。商品化鉆頭的鉆頂角一般為118°，這適用于鉆削低碳鋼和鑄鐵。Forharderandtoughermetals,suchashardenedsteel,brassandbronze,largerTPAs(130°or140°)givebetterperformance.Thehelixangleoftheflutesofthecommonlyusedtwistdrillsrangesbetween24°and30°.Whendrillingcopperorsoftplastics,highervaluesforthehelixanglearerecommended(between35°and45°).對于更硬更韌的金屬，諸如淬火鋼、黃銅和青銅，更大的鉆頂角(130°或140°)才能有更好的效果。麻花鉆常用的出屑槽螺旋角范圍為24°到30°。鉆削紫銅或軟塑料時，推薦采用更大的螺旋角(35°到45°)。Twistdrillsareusuallymadeofhigh-speedsteel,althoughcarbide-tippeddrillsarealsoavailable.Thesizesoftwistdrillsusedinindustrialpracticerangefrom0.01upto3.25in.(i.e.,0.25upto80mm).

雖然也有硬質合金刀尖的鉆頭，麻花鉆一般用高速鋼制成。工業(yè)實際中使用的麻花鉆尺寸范圍為0.01到3.25英寸(即0.25到80毫米)。

Coredrills.Acoredrillconsistsofthechamfer,body,neck,andshank,asshowninFig.12.2.Thistypeofdrillmayhaveeitherthreeorfourflutesandequalnumberofmargins,whichensuresuperiorguidance,thusresultinginhighmachiningaccuracy.

空心鉆：空心鉆包括斜面、鉆頭體、鉆頸和鉆柄，如圖12.2所示。這類鉆頭可以有三條或四條出屑槽及相同數(shù)量的保證良好導向的導向邊，這樣使得加工有高精度。ItcanalsobeseeninFig.12.2thatacoredrillhasflatend.Thechamfercanhavethreeorfourcuttingedgesorlips,andthelipanglemayvarybetween90°and120°.在圖12.2中同樣能看到，空心鉆具有平坦的端部。斜面可以有三或四條切削刃或鉆唇，并且鉆唇角可以在90°到120°之間變化。Coredrillsareemployedforenlargingpreviouslymadeholesandnotfororiginatingholes.Thistypeofdrillischaracterizedbygreaterproductivity,highmachiningaccuracy,andsuperiorqualityofthedrilledsurfaces.空心鉆用于擴大已有的孔而不是打孔。這類鉆頭具有較大生產(chǎn)率、高加工精度和優(yōu)良鉆削表面質量的特性。Gundrills.Gundrillsareusedfordrillingdeepholes.Allgundrillsarestraight-fluted,andeachhasasinglecuttingedge.Aholeinthebodyactsasaconduittotransmitcoolantunderconsiderablepressuretothetipofthedrill.

深孔鉆：深孔鉆用于鉆深孔。所有深孔鉆都是直出屑槽的，并且均為單切削刃。鉆頭體中有個孔作為導管在相當大的壓力下將冷卻液傳送到鉆頭頂端。

Therearetwokindsofgundrills,namely,thecenter-cutgundrillusedfordrillingblindholesandthetrepanningdrill.Thelatterhasacylindricalgrooveatitscenter,thusgeneratingasolidcore,whichguidesthetoolasitproceedsduringthedrillingoperation.深孔鉆有兩種類型，即用于鉆盲孔的中心切削深孔鉆和套孔鉆。后者在其中心有一圓柱形溝槽，這樣能生成整體芯在鉆孔作業(yè)過程中引導鉆頭。Spadedrills.Spadedrillsareusedfordrillinglargeholesof3.5in.(90mm)ormore.Theirdesignresultsinamarkedsavingincostofthetoolaswellasatangiblereductioninitsweight,whichfacilitatesitshandling.Moreover,thistypeofdrilliseasytogrind.

扁平鉆：扁平鉆用于鉆削3.5英寸(90毫米)或更大的大孔。其設計使得鉆頭成本明顯節(jié)省、重量切實減輕，重量輕又使操作更方便。此外這種鉆頭容易磨利。MillingandMillingCutter銑削和銑刀Millingisamachiningprocessthatiscarriedoutbymeansofamultiedgerotatingtoolknownasamillingcutter.

銑削是采用被稱為銑刀的多刃旋轉刀具完成的機加工作業(yè)。Inthisprocess,metalremovalisachievedthroughcombiningtherotarymotionofthemillingcutterandlinearmotionsoftheworkpiecesimultaneously.Millingoperationsareemployedinproducingflat,contouredandhelicalsurfacesaswellasforthread-andgear-cuttingoperation.在此工藝中，金屬去除是通過銑刀的旋轉運動和工件的直線運動的組合實現(xiàn)的。銑削作業(yè)既可用于生成平面、輪廓面和螺旋面，也可用于切削螺紋和齒輪。Eachofthecuttingedgesofamillingcutteractsasanindividualsingle-pointcutterwhenitengageswiththeworkpiecemetal.Therefore,eachofthosecuttingedgeshasappropriaterakeandreliefangles.

在銑刀切削工件金屬時，銑刀的每條切削刃都象一單獨的單刃刀具一樣作用。所以每條切削刃都適當?shù)那昂蠼?。Sinceonlyafewofthecuttingedgesareengagedwiththeworkpieceatatime,heavycutscanbetakenwithoutadverselyaffectingthetoollife.Infact,thepermissiblecuttingspeedsandfeedsformillingarethreetofourtimeshigherthanthoseforturningordrilling.由于同一時間只有部分切削刃切削工件，因此可以在對刀具壽命沒有不利影響的情況下承擔重型切削。事實上，銑削允許的切削速度和進給比車削或鉆削高三到四倍。Moreover,thequalityofthesurfacesmachinedbymillingisgenerallysuperiortothequalityofsurfacesmachinedbyturning,shaping,ordrilling.此外，由銑削加工的表面質量通常優(yōu)于車削、刨削或鉆削加工的表面質量。

Awidevarietyofmillingcuttersisavailableinindustry.This,togetherwiththefactthatamillingmachineisaveryversatilemachinetool,makesthemillingmachinethebackboneofamachiningworkshop.

工業(yè)上可采用的銑刀類型眾多。連同銑床是極通用機床的事實，使得銑床成為機加工車間的支柱。

Asfarasthedirectionofcutterrotationandworkpiecefeedareconcerned,millingisperformedbyeitherofthefollowingtwomethods.

至于涉及到銑刀轉動的方向和工件的進給，銑削可以通過下列兩種方法之一進行。Upmilling(conventionalmilling).Inupmillingtheworkpieceisfedagainstthedirectionofcutterrotation,asshowninFig.12.3a.Aswecanseeinthatfigure,thedepthofcut(andconsequentlytheload)graduallyincreasesonthesuccessivelyengagedcuttingedges.

逆銑(傳統(tǒng)銑削)：在逆銑中，工件逆著銑刀轉動的方向進給，如圖12.3a所示。就像在此圖中能看到的那樣，切削深度(及作為結果的載荷)隨著切削刃持續(xù)進入切削而逐漸增加。Therefore,themachiningprocessinvolvesnoimpactloading,thusensuringsmootheroperationofthemachinetoolandlongertoollife.Thequalityofthemachinedsurfaceobtainedbyupmillingisnotveryhigh.Nevertheless,upmillingiscommonlyusedinindustry,especiallyforroughcuts.所以，這種工藝沒有沖擊載荷，從而保證了機床的較平穩(wěn)運行和較長壽命。通過逆銑所得機加工表面質量不是很高。然而逆銑仍經(jīng)常被用在工業(yè)上，尤其是粗切削時。Downmilling(climbmilling).AscanbeseeninFig.12.3b,indownmillingthecutterrotationcoincideswiththedirectionoffeedatthecontactpointbetweenthetoolandtheworkpiece.Itcanalsobeseenthatthemaximumdepthofcutisachieveddirectlyasthecutterengageswiththeworkpiece.

順銑(同向銑削)：如同在圖12.3b中看到的那樣，在順銑時刀具與工件之間接觸點上銑刀旋轉與進給方向一致。還可以看到當?shù)毒哌M入工件切削時直接達到最大切削深度。Thisresultsinakindofimpact,orsuddenloading.Therefore,thismethodcannotbeusedunlessthemillingmachineisequippedwithabacklasheliminatoronthefeedscrew.Theadvantagesofthismethodincludehigherqualityofthemachinedsurfaceandeasierclampingofworkpieces,sincethecuttingforcesactdownward.這會導致一種沖擊，或突然加載。因此，這種方法只有當銑床在進給螺栓上配備間隙消除器時才采用。這種方法的優(yōu)點包括機加工表面質量較高和工件由于切削力向下作用而較容易夾緊。TypesofMillingCutters

Thereisawidevarietyofmillingcuttershapes.Eachofthemisdesignedtoperformeffectivelyaspecificmillingoperation.銑刀的類型

銑刀的形狀類型很多。其中每種都是為有效進行特定的銑削作業(yè)而設計的。Generally,amillingcuttercanbedescribedasamultiedgecuttingtoolhavingtheshapeofasolidofrevolution,withthecuttingteetharrangedeitherontheperipheryoronanendfaceoronboth.Followingisaquicksurveyofthecommonlyusedtypesofmillingcutters.通常，銑刀可以被描述為具有旋轉實體形狀并將切削齒安裝在周邊或一到兩個端面上的多刃切削刀具。下面是常用銑刀類型的快速綜覽。Plainmillingcutter.Aplainmillingcutterisadisk-shapedcuttingtoolthatmayhaveeitherstraightorhelicalteeth,asshowninFig.12.4a.Thistypeisalwaysmountedonhorizontalmillingmachinesandisusedformachiningflatsurfaces.

平面銑刀：平面銑刀是一種盤狀切削刀具，它可以具有直齒或螺旋齒，如圖12.4a所示。這類銑刀總是安裝在臥式銑床上，用于機加工平面。

Facemillingcutter.Afacemillingcutterisalsousedformachiningflatsurfaces.Itisboltedattheendofashortarbor,whichisinturnmountedonaverticalmillingmachine.Fig.12.4bindicatesamillingcutterofthistype.

端面銑刀：端面銑刀也可用于機加工平面。它用螺栓固定在短刀桿的端部，而短刀桿則依次安裝于立式銑床上。圖12.4b顯示了這類銑刀。Plainmetalslittingsawcutter.Fig.12.4cindicatesaplainmetalslittingsawcutter.wecanseethatitactuallyinvolvesaverythinplainmillingcutter.

平面金屬開槽鋸刃銑刀：圖12.4c顯示了一種平面金屬開槽鋸刃銑刀?？梢钥吹剿鋵嵤且环N很薄的平面銑刀。

Sidemillingcutter.Asidemillingcutterisusedforcuttingslots,grooves,andsplines.AsshowninFig.12.4d,itisquitesimilartotheplainmillingcutter,thedifferencebeingthatthistypehasteethonthesides.Asisthecasewiththeplaincutter,thecuttingteethcanbestraightorhelical.

側銑刀：側銑刀用于切削狹槽、凹槽和花鍵槽。正如圖12.4d所示，它與平面銑刀十分相似，差別在于此類銑刀齒在側面。象平面銑刀的情況一樣，切削齒既可以是直的也可以是螺旋的。

Anglemillingcutter.Ananglemillingcutterisemployedincuttingdovetailgrooves,ratchetwheels,andthelike.Fig.12.4eindicatesamillingcutterofthistype.

傾斜銑刀：傾斜銑刀用于切削燕尾槽、棘輪之類的。圖12.4e顯示了這類銑刀。T-slotcutter.AsshowninFig.12.4f,aT-slotcutterinvolvesaplainmillingcutterwithanintegralshaftnormaltoit.Asthenamesuggests,thistypeisusedformillingT-slots.

T型槽銑刀：如圖12.4f所示，T型槽銑刀包括了一個平面銑刀和一根垂直于它的整體軸。正像其名字所表明的，這類銑刀用于銑削T型槽。

Endmi