泵體工藝外文翻譯

泵體工藝外文翻譯泵體工藝外文翻譯泵體工藝外文翻譯V:1.0精細(xì)整理，僅供參考泵體工藝外文翻譯日期：20xx年X月本科生畢業(yè)設(shè)計(jì)(論文)外文翻譯原文標(biāo)題BasicMachiningOperations—Turning,BoringandMilling譯文標(biāo)題基本的加工工序—切削，鏜削和銑削作者所在系別機(jī)械工程系作者所在專業(yè)機(jī)械設(shè)計(jì)制造及其自動(dòng)化作者所在班級(jí)作者姓名作者學(xué)號(hào)指導(dǎo)教師姓名指導(dǎo)教師職稱完成時(shí)間年月北華航天工業(yè)學(xué)院教務(wù)處制譯文標(biāo)題基本的加工工序—切削，鏜削和銑削原文標(biāo)題BasicMachiningOperations—Turning,BoringandMilling作者B.W.Nile譯名本.沃.聶邇國(guó)籍加拿大原文出處ModernManufacturingProcessEngineering譯文：基本的加工工序機(jī)床是從早期的埃及人的腳踏動(dòng)力車床和約翰.威爾金森的鏜床發(fā)展而來的。它們用于為工件和刀具兩者提供剛性支撐并且可以精確控制它們的相對(duì)位置和相對(duì)速度。一般來說，在金屬切削中用一個(gè)磨尖的楔形工具以緊湊螺紋形的切屑形式從有韌性工件表面上去除一條很窄的金屬。切屑是廢棄的產(chǎn)品，與其工件相比，它相當(dāng)短但是比未切削的部分厚度有相對(duì)的增加。機(jī)器表面的幾何形狀取決于刀具的形狀以及加工過程中刀具的路徑。不同的加工工序生產(chǎn)出不同幾何形狀的部件。如果一個(gè)粗糙的柱形工件繞中心軸旋轉(zhuǎn)而且刀具穿透工件表面并沿與旋轉(zhuǎn)中心平行的方向前進(jìn)，就會(huì)產(chǎn)生一個(gè)旋轉(zhuǎn)面，這道工序叫車削。如果以類似的方式加工一根空心管的內(nèi)部，則這道工序就叫鏜削。制造一個(gè)直徑均勻變化的錐形外表面叫做錐體車削。如果刀具尖端以一條半徑可變的路徑前進(jìn)，就可以制造出象保齡球桿那種仿形表面；如果工件足夠短而且支撐具有足夠的剛性，仿形表面可以通過用一個(gè)垂直于旋轉(zhuǎn)軸的仿形刀具來制造。短的錐面或柱面也可以仿形切削。常常需要的是平坦的或平的表面。它們可以通過徑向車削或端面車削來完成，其中刀具尖端沿垂直于旋轉(zhuǎn)軸的方向運(yùn)動(dòng)。在其他情況下，更方便的是固定工件不動(dòng)，以一系列直線方式往復(fù)運(yùn)動(dòng)刀具橫過工件，在每次切削行程前具有一定橫向進(jìn)給量。這種龍門刨削和牛頭刨削是在刨床上進(jìn)行的。大一些的工件很容易保持刀具固定不動(dòng)，而像龍門刨削那樣在其下面拉動(dòng)工件，再每次往復(fù)進(jìn)給刀具。仿形面可以通過使用仿形刀具來制造。也可以使用多刃刀具。鉆削使用兩刃刀具，深度可達(dá)鉆頭直徑的5-10倍。不管是鉆頭轉(zhuǎn)動(dòng)還是工件轉(zhuǎn)動(dòng)，切削刃與工件之間的相對(duì)運(yùn)動(dòng)都是一個(gè)重要因素。在銑削作業(yè)中，有許多切削刃的旋轉(zhuǎn)銑刀與工件相接合，這種工件相對(duì)銑刀運(yùn)動(dòng)緩慢。根據(jù)銑刀的幾何形狀和進(jìn)給的方式，可以加工出平面和仿形面?？梢允褂盟交虼怪毙D(zhuǎn)軸，工件可以沿三個(gè)坐標(biāo)方向中的任意一個(gè)進(jìn)給?；镜臋C(jī)床機(jī)床用于以切屑的形式從韌性材料上去除金屬來加工特殊幾何形狀和精密尺寸的部件。切屑是廢品，其變化形狀從像鋼這樣的韌性材料的長(zhǎng)的連續(xù)帶狀屑到鑄鐵形成的易于處理、徹底斷掉的切屑，從處理的觀點(diǎn)來講，不想要長(zhǎng)的連續(xù)帶狀屑。機(jī)床完成5種基本的金屬切削工藝：車削、刨削、鉆削、銑削和磨削。其他所有金屬切削工藝都是這5種基本工藝的變形。例如：鏜削是內(nèi)部車削；鉸削、錐體車削和平底锪孔則修改鉆孔，與鉆削有關(guān)；滾齒與切齒是基本銑削作業(yè)；弓鋸削和拉削是銑削和磨削的一種形式；而研磨、超精加工、拋光和磨光是磨削和研磨切削作業(yè)的各種變化形式。因此，僅有4種使用專用可控幾何形狀的刀具基本機(jī)床：1、車床，2、刨床，3、鉆床，4、銑床。磨削工藝形成碎屑，但是磨粒的幾何形狀不可控制。不同加工工藝切削的材料的數(shù)量和速度卻不相同?？赡軜O大，如大型車削作業(yè)；或者極小，如磨削和超精加工作業(yè)，只有表面高出的點(diǎn)被去除。機(jī)床完成3種主要功能：1、剛性支撐工件或工件夾具以及切削刀具；2、提供工件與切削刀具之間的相對(duì)運(yùn)動(dòng)；3、提供了一定范圍的速度進(jìn)給，通常每種有4-32種選擇。切削速度和進(jìn)給切削速度、進(jìn)給量和切削深度是切削加工的3個(gè)主要變量，其他變量還有工件和工具材料、冷卻劑以及切削刀具的幾何形狀。金屬切削的速率和加工所需的功率就決定于這些變量。切削深度、進(jìn)給量和切削速度是任何金屬切削作業(yè)中必須都建立的變量。它們都影響切削力、功率和對(duì)金屬切削的速率?？梢酝ㄟ^把它們與留聲機(jī)的唱針和唱片相比較給出定義。切削速度（V）由任意時(shí)刻唱片表面相對(duì)于拾音器支臂內(nèi)部的唱針的速度來表示；進(jìn)給量由唱針每圈徑向向內(nèi)的前進(jìn)量或者由兩個(gè)相鄰槽的位置差來表示。切削深度是唱針進(jìn)入的量或者是槽的深度。切削那些在外表面上用單刃刀具完成的工序叫車削。除鉆削、鉸削和錐體車削外，在內(nèi)表面的作業(yè)也由單刃刀具完成。包括車削和鏜削在內(nèi)的所有加工工序都可以分為粗加工、精加工和半精加工。粗加工工序的目的是盡可能迅速且高效地去除大量的材料，在工件上只留下少量的材料給精加工工序。精加工工序用以獲得工件最終的大小、形狀和表面粗糙度。有時(shí)，在精加工工序前進(jìn)行半精加工作業(yè)以便在工件上留下少的、預(yù)定的和均勻量的原材料供精加工去除。通常，較長(zhǎng)的工件是在一個(gè)或兩個(gè)車床頂尖的支撐下進(jìn)行的。用于安裝車床頂尖的錐形孔叫做頂尖孔，它是在工件的端部鉆出的——通常沿著柱形部件的軸心。與尾架鄰近的工件端部總是由尾架頂尖支撐，而挨著主軸箱的一端則由主軸箱頂尖支撐或裝在卡盤內(nèi)。工件的主軸箱一端可以裝在一個(gè)四爪卡盤或套爪卡盤內(nèi)。這種方法牢固地夾持工件并且把功率平穩(wěn)地傳送到工件上；由卡盤提供的額外支撐減少了車削作業(yè)時(shí)發(fā)生震動(dòng)的傾向。如果仔細(xì)地將工件精確的固定在卡盤上，用這種方法將獲得精密的結(jié)果。通過將工件支撐在兩個(gè)頂尖之間可以獲得非常精確的結(jié)果。一個(gè)車床夾頭夾在工件上；然后由安裝在主軸前端的撥盤一起帶動(dòng)。先加工工件的一端，然后可以在車床上將工件掉頭加工另一端。工件上的頂尖孔是用作精確定位面以及承受工件重量和抵抗車削力的支撐面。在工件被拆下后，頂尖孔可以精確地將其裝回機(jī)床。工件千萬不要同時(shí)通過卡盤和頂尖安裝在主軸箱一端。雖然這樣似乎是一種快捷方法，但是這樣做使得工件受力不均勻，頂尖的對(duì)正作用不能維持，而且爪的壓力可能損壞頂尖孔、車床頂尖甚至車床主軸。幾乎被獨(dú)自用在大量生產(chǎn)工件上的補(bǔ)償或浮動(dòng)爪式卡盤是上述的一個(gè)例外。這些卡盤是自動(dòng)偏心夾緊卡盤不能起到普通三爪或四爪卡盤同樣的作用。直徑非常大的工件雖然有時(shí)安裝在兩個(gè)頂尖上，但是最好用花盤把它們固定在主軸箱端以獲得流暢的動(dòng)力傳輸；此外，可以把它們制造成專用部件，但是一般不能提供足夠大的車床夾頭來傳輸動(dòng)力。除非是安裝在花盤上，其主軸軸承上的外伸要比大卡盤上的少一些。鏜削在車床上鏜孔的目的是：1、擴(kuò)孔；2、把孔加工到所需直徑；3、精確的為孔定位；4、在孔內(nèi)獲得好的表面粗糙度。當(dāng)?shù)毒邚较蛄锇蹇v向移動(dòng)而工件繞車床的軸線旋轉(zhuǎn)時(shí)，鏜刀的運(yùn)動(dòng)平行于車床上的軸線。當(dāng)兩種運(yùn)動(dòng)結(jié)合起來鏜孔時(shí)，就會(huì)與車床的旋轉(zhuǎn)軸同心。通過把工件固定在車床上可以精確定位孔的位置以使待加工孔所環(huán)繞的軸與車床的旋轉(zhuǎn)軸一致。當(dāng)鏜削工序與用于車削和刮削工序的設(shè)置相同時(shí)，實(shí)際上可以達(dá)到理想的同心與垂直。鏜刀固定在一根通過刀具徑向溜板進(jìn)給的鏜桿上。根據(jù)待做的工作來使用這一設(shè)計(jì)的變化形式。如果有的話，所用的倒角總是應(yīng)該小些。而且，鏜刀前端的半徑一定不能太大。用于鏜孔的切削速度可以等于車削速度。但是，在計(jì)算車床主軸速度時(shí)，應(yīng)當(dāng)使用完成后的或最大的孔徑。鏜削的進(jìn)刀速度通常比車削的小一點(diǎn)以補(bǔ)償鏜桿剛性的不足。鏜削工序一般分兩步完成，即粗鏜和精鏜。粗鏜工序的目的是快速、高效地去除多余的金屬；而精鏜工序的目的是獲得所需的尺寸、表面粗糙度和孔的位置。孔的尺寸通過試切來獲得。孔的直徑可以用內(nèi)卡尺和千分尺測(cè)量。測(cè)量?jī)x表或內(nèi)千分卡尺直接測(cè)量直徑。型心孔和要鉆的孔有時(shí)相對(duì)于車床的旋轉(zhuǎn)是偏心的。當(dāng)鏜刀進(jìn)入工件時(shí)，鏜桿在孔的一邊切口比另一邊深，當(dāng)采用這深切口時(shí)就會(huì)更偏斜，結(jié)果鏜的孔與工件旋轉(zhuǎn)不同心。這一影響通過利用淺切口在整個(gè)孔加工中進(jìn)行幾次加工來糾正。因?yàn)槊總€(gè)淺切口形成的孔比使用深切口形成的孔更加同心。在完工前，進(jìn)行精加工，孔應(yīng)該與工件的旋轉(zhuǎn)同心以確保完工時(shí)孔能精確定位。肩、溝槽、輪廓、錐度和螺紋也應(yīng)該在孔內(nèi)鏜出。內(nèi)槽是用與外部開槽工具相似的工具切削。鏜削內(nèi)槽的步驟非常類似于車削肩部的步驟。大的肩部使用前導(dǎo)裝置定位的鏜刀進(jìn)行刮削，使用橫向滑板進(jìn)給工具。內(nèi)部輪廓使用車床上的描摹附件加工。仿行板附件安裝在橫向滑板上，靠模指跟隨標(biāo)準(zhǔn)剖面板的輪廓線運(yùn)動(dòng)。這使刀具對(duì)應(yīng)于標(biāo)準(zhǔn)剖面樣板的輪廓線的路徑進(jìn)行移動(dòng)。這樣標(biāo)準(zhǔn)剖面樣板的輪廓就在孔內(nèi)得到復(fù)制。標(biāo)準(zhǔn)剖面樣板精確安裝在一個(gè)專用的滑板上，滑板可以在兩個(gè)方向上進(jìn)行精確調(diào)整以使刀具與工件以正確的關(guān)系對(duì)正。這臺(tái)車床有一個(gè)偏心夾型的主軸前端，允許在任意一方向旋轉(zhuǎn)時(shí)進(jìn)行切削。正常的車削是在主軸逆時(shí)針轉(zhuǎn)動(dòng)時(shí)進(jìn)行的；鏜削切削是在主軸順時(shí)針方向或“向后”轉(zhuǎn)動(dòng)時(shí)進(jìn)行的。這允許在孔的“后側(cè)”進(jìn)行鏜削切削，在車床前面，從操作者的位置易于看到后孔。在具有螺紋主軸前端的車床上不應(yīng)這么做，因?yàn)榍邢髁Φ淖饔脮?huì)旋松卡盤。銑削銑削是一種通過工件與多刃旋轉(zhuǎn)銑刀間的相對(duì)運(yùn)動(dòng)去除材料的加工工藝。在一些應(yīng)用中，工件固定而旋轉(zhuǎn)的銑刀以一定進(jìn)給速度移過工件（橫向進(jìn)給）；在其他應(yīng)用中，工件與銑刀既彼此相對(duì)運(yùn)動(dòng)，又相對(duì)銑床運(yùn)動(dòng)。但是，更常見的是工件以一個(gè)相對(duì)較低的運(yùn)動(dòng)速度或進(jìn)給速度朝正在高速旋轉(zhuǎn)的銑刀前進(jìn)，而銑刀軸保持在一個(gè)固定位置。銑削工藝特有的性能是每個(gè)銑刀齒都以小的單個(gè)切屑的形式切去一部分原料。可以在許多不同的機(jī)器上進(jìn)行銑削作業(yè)。由于工件和銑刀都可以彼此相對(duì)運(yùn)動(dòng)，銑削可以獨(dú)立的或以組合方式完成各式各樣的作業(yè)。各種應(yīng)用包括平面或仿行面、窄槽、槽、退刀槽、螺紋和其他外形的加工。銑削是一種最為通用而又復(fù)雜的加工方法。該工藝比任何其他基本加工方法在所用機(jī)器的種類、工件運(yùn)動(dòng)以及加工工具種類方面都具有更多的變化。利用銑削去除材料的重要優(yōu)點(diǎn)包括原料切削速度高，能形成相對(duì)光滑的表面粗糙度以及可應(yīng)用的刀具更為多樣。刀具的切削刀刃可以仿行以形成任何復(fù)雜的表面。主要的銑削方法有周銑和端銑，此外，還有許多相關(guān)方法，他們屬于這2種方法的變化形式，這些變化形式取決于工件或刀具的類型。周銑在周銑（有時(shí)也叫平面銑削）中，由位于銑刀主體外周上的尺或刀片銑削的面一般在一個(gè)與銑刀軸平行的平面上。使用鏟齒銑刀和成形銑刀完成的銑削工序包括在這一類。銑削面的界面與所使用的銑刀或刀具組合的輪廓線或輪廓相符。周銑作業(yè)通常在帶有水平定位主軸的銑床上進(jìn)行。但也可以在帶有端面銑刀的主軸銑床上進(jìn)行。銑刀安裝在心軸上，尤其是由于設(shè)置的條件，銑刀或者若干銑刀位于距主軸前端一定距離處時(shí)，心軸一般在外端得到支撐來提高剛性。如果部件可以端銑，一般不應(yīng)進(jìn)行周銑。端銑端銑在臥式銑床和立式銑床上進(jìn)行。由位于銑刀外周和端面的切削刃聯(lián)合銑削所形成的銑削面一般與銑刀軸成直角。除了在肩部銑削時(shí)外，銑削面是平的，與齒的輪廓形狀無關(guān)。一般來講，無論何時(shí)何地，只要可能就應(yīng)使用端銑。傳統(tǒng)（上）端銑中切屑厚度是變化的，在銑刀齒進(jìn)入和退出處最薄，而在沿水平直徑處最大。銑削面由齒和專屬轉(zhuǎn)速痕跡表現(xiàn)其特征，這與周銑銑刀情況相同。這些痕跡的起伏度由齒的端面切削刃的磨削精度或由刀體/刀片在可以指標(biāo)化的刀具內(nèi)組合精度以及刀具安裝精度來控制，以使刀具在主軸上精確運(yùn)動(dòng)。起伏度還由機(jī)器及工件本身的剛性來控制。當(dāng)端面切削刃的長(zhǎng)度短于每轉(zhuǎn)的進(jìn)給量（或銑刀每轉(zhuǎn)一圈工件的移動(dòng)量）時(shí)，在銑面上就會(huì)形成一系列的環(huán)形凹槽或環(huán)紋。當(dāng)后齒在工件的銑面上拖動(dòng)時(shí)，也會(huì)產(chǎn)生類似的標(biāo)記，這叫齒根拖動(dòng)。在端銑中，如果想獲得最佳結(jié)果，重要的是選擇銑刀具有適于所建議的切削寬度的直徑。如果可能，應(yīng)避免切削寬度等與銑刀外徑相同，因?yàn)樵邶X的入口處，薄的銑屑界面會(huì)由于研磨加上銑屑有焊或粘到齒或刀片上并被帶來帶去或再次切削的趨向而導(dǎo)致齒的加速磨損。這對(duì)表面粗糙度是有害的。好的銑刀直徑與工件或提議的切削路線寬度之比是5：3。原文：BasicMachiningOperationsMachiningtoolshaveevolvedfromtheearlyfoot–poweredlatheEgyptiansandJohnWilkinson’sboringmill.Theyaredesignedtoproviderigidsupportforboththeworkpieceandthecuttingtoolandcuttingtoolandcanpreciselycontroltheirrelativepositionsandthevelocityofthetoolwithrespecttotheworkpiece.Basically,inmetalcutting,asharpenedwedge-shapedtoolremovesarathernarrowstripofmetalfromthesurfaceofaductileworkpieceinthefromofaseverelydeformedchip.Thechipiswasteproductthatisworkpieceinthefromofaseverelydeformedchipisawasteproductthatisconsiderablyshorterthantheworkpiecefromwhichitcamebutwithacorrespondingincreaseinthicknessoftheuncutchip.Thegeometricalshapeofthemachinesurfacedependsontheshapeofthetoolanditspathduringthemachiningopration.Mostmachineoperationsproducepartsofdifferinggeometry.Ifaroughcylindricalworkpiecerevolvesaboutacentralaxisandtoolpenetratesbeneathitssurfaceandtravelsparalleltothecenterofrotation,asurfaceofrevolutionisproduced,andtheoperationiscalledturning.Ifahollowtubeisonthemachinedontheinsideinasimilarmanner,theoperationiscalledboring.Producinganexternalconicalsurfaceofuniformlyvaryingdiameteriscalledtaperturning.Ifthetoolpointtravelsinapathofvaryingradius,acontouredsurfacelikethatofbowlingpincanbeproduced;or,ifthepieceisshortenoughandthesupportissufficientlyrigid,acontouredsurfacecouldbeproducedbyfeedingashapedtoolnormaltotheaxisofrotation.Shorttaperedorcylindricalsurfacescouldalsobecontourformed.Flatorplanesurfacearefrequentlyrequired.Theycanbegeneratedbyradialturningorfacing,inwhichthetoolpointmovesnormaltotheaxisofrotation.Inothercases,itismoreconvenienttoholetheworkpiecesteadyandreciprocatethetoolacross,itisseriesofstraight-linecutswithacrosswisefeedincrementbeforeeachcuttingstroke.Thisoperationiscalledplanningandiscarriedoutonashaper.Forlargerpiecesitiseasiertokeepthetoolstationaryanddrawtheworkpieceunderitasinplanning.Thetoolisfedateachreciprocation.Contouredsurfacescanbeproducedbyusingshapedtools.Multiple-edgedtoolscanalsobeused.Drillingusesatwin-edgedflutedtoolforholeswithdepthsupto5to10timesthedrilldiameter.Whetherthedrillturnsortheworkpiecerotates,relativemotionbetweenthecuttingedgeandtheworkpieceistheimportantfactor.Inmillingoperationsarotarycutterwithanumberofcuttingedgesengagestheworkpiece,whichmovesslowlywithrespecttothecutter.Planeorcontouredsurfacesmaybeproduced,dependingonthegeometryofthecutterandthetypeoffeed.Horizontalorverticalaxesofrotationmaybeused,andthefeedoftheworkpiecemaybeinanyofthethreecoordinatedirections.BasicMachineToolsMachinetoolsareusedtopartofaspecifiedgeometetricalshapeandprecisesizebyremovingmetalfromaductilematerialintheformchips.Thelatterareawasteproductandvaryfromlongcontinuousribbonsofadisposalpointofview,toeasilyhandedwell-brokenchipsresultingfromcastiron.Machinetoolsperformfivebasicmetal-removeprocesses:turning,planning,drilling,milling,andgrinding.Allothermetal-removalprocessesaremodificationsofthesefivebasicprocesses.Forexample,boringisinternalturning;reaming,tapping,andcounterboringmollifydrilledholesandarerelatedtodrilling;hobblingandgearcuttingarefundamentallymillingoperations;hacksawingandbroachingareafromofplanningandhoning;lapping,superfinishing,polishing,andbuffingarevariantsofgrindingorabrasiveremovaloperations.Therefore,thereareonlyfourtypesofbasicmachinetools,whichusecuttingtoolsofspecificcontrollablegeometry.Thegrindingprocessformschips,butthegeometryoftheabrasivegrainisuncontrollable.Theamountandrateofmaterialremovedbythevariousmachiningprocessesmaybelarge,asinheavyturningoperations,orextremelysmall,asinlappingorsuperfinishingoperationswhereonlythehighspotsofasurfaceareremoved.Amachiningtoolperformsthreemajorfunctions:1.itrigidlysupportstheworkpiceoritsholderandthecuttingtool;2.itprovidesrelativemotionbetweentheworkpiceandthecuttingtool;3.itprovidesarangeoffeedsandspeedsusuallyrangingfrom4to32choicesineachcase.SpeedandFeedsinMachiningSpeeds,feeds,anddepthpfcutarethethreemajorvariablesforeconomicalmachining.Othervariablesaretheworkandtoolmaterials,coolantandgeometryofthecuttingtool.Therateofmetalremovalandpowerrequiredformachiningdependuponthesevariables.Thedepthsofcut,feed,andcuttingspeedaremachinesettingthatmustbeestablishedinanymetal-cuttingoperation.Theyallaffecttheforces,thepower,andtherateofmetalremoval.Theycanbedefinedbycomparingthemtotheneedleandrecordofaphonograph.Thecuttingspeed(V)isrepresentedbythevelocityoftherecordsurfacerelativetotheneedleinthetonearmatanyinstant.Feedisrepresentedbytheadvanceoftheneedleradiallyinwardperrevolution,oristhedifferenceinpositionbetweentwoadjacentgrooves.Thedepthofcutisthepenetrationoftheneedleintotherecordorthedepthofthegrooves.TurningonlathecentersThebasicoperationsoperationsperformedonanenginelatheareillustratedinfig.11-3.thoseoperationsperformedonexternalsurfaceswithasinglepointcuttingtoolarecalledturning.Exceptfordrilling,reaming,andtapping,theoperationsoninternalsurfacesarealsoperformedbyasinglepointcuttingtool.Allmachiningoperate,includingturningandboring,canbeclassifiedasroughing,finishing,orsemi-finishing.Theobjectiveofaroughingoperationistoremovethebulkofthematerialasrapidlyandasefficientlyaspossible,whileleavingasmallamountofmaterialonthework-pieceforthefinishingoperation.Finishingoperationsareperformedtoobtainthefinalsize,shape,andsurfacefinishontheworkpiece.Sometimesasemi-finishingoperationwillprecedethefinishingoperationtoleaveasmallpredeterminedanduniformamountofstockonthework-piecetoberemovedbythefinishingoperation.Generally,longerworkpiecesareturnedwhilesupportedononeortwolathecenters.Coneshapedholes,calledcenterholes,whichfitthelathecentersaredrilledintheendoftheworkpiece-usuallyalongtheaxisofthecylindricalpart.Theendoftheworkpieceadjacenttothetailstockisalwayssupportedbyatailstockcenter,whileendneartheheadstockmaybesupportedbyaheadstockcenterorheldinachuck.Theheadstockendoftheworkpiecemaybeheldinafour-jawchuck,orinacollettypechuck.Thismethodholdstheworkpiecefirmlyandtransfersthepowertotheworkpiecesmoothly;theadditionalsupporttotheworkpieceprovidedbythechucklessensthetendencyforchattertooccurwhencutting.Preciseresultcanbeobtainedwiththismethodifcareistakentoholdtheworkpieceaccuratelyinthechuck.Verypreciseresultscanbeobtainedbysupportingtheworkpiecebetweentwocenters.Alathedogisclampedtotheworkpiece;togethertheyaredrivenbythedriverplatemountedonthespindlenose.Oneendoftheworkpieceismachined;thentheworkpiececanbeturnedaroundinthelathetomachinetootherend.Thecenterholesintheworkpieceserveaspreciselocatingsurfacesaswellasbearingsurfacestocarrytheweightoftheworkpieceandtoresistthecuttingforces.Aftertheworkpiecehasbeenremovefromthelatheforanyreason,thecenterholeswillaccuratelyaligntheworkpiecebackinthelatheorinanotherlathe,orinacylindricalgrindingmachine.Theworkpiecemustneverbeheldattheheadstockendbybothachuckandalathecenter.Whileatfirstthoughtthisseemslikeaquickmethodofaligningtheworkpieceinthechuck,thismustnotbedonebecauseitisnotpossibletopressevenlywiththejawsagainsttheworkpiecewhileitisalsosupportedbythecenter.Thealignmentprovidedbythecenterwillnotbemaintainedandthepressureofthejawsmaydamagethecenterhole,thelathecenter,andperhapseventhelathespindle.Compensatingorfloatingjawchucksusedalmostexclusivelyonhighproductionworkprovideanexceptiontothestatementsmadeabove.Thesechucksarereallyworkdriversandcannotbeusedforthesamepurposeasordinarythreeorfour-jawchicks.Whileverylargediameterworkpiecearesometimesmountedontwocenters,theyarepreferablyheldattheheadstockendbyfaceplatejawstoobtainthesmoothpowertransmission;moreover,largelathedogsthatareadequatetotransmitthepowernotgenerallyavailable,althoughtheycanbemadeasaspecial.Faceplatejawsarelikechuckjawsexceptthattheyaremountedonafaceplate,whichhaslessoverhangfromthespindlebearingsthanalargechuckwouldhave.BoringTheobjectiveofboringaholeinalatheis:1、Toenlargethehole2、Tomachinetheholetothedesireddiameter3、Toaccuratelylocatethepositionofthehole4、ToobtainasmoothsurfacefinishintheholeThemotionoftheboringtoolisparalleltotheaxisofthelathewhenthecarriageismovedinthelongitudinaldirectionandtheworkpiecerevolvesabouttheaxisofthelathe.Whenthesetwomotionsarecombinedtoboreahole,itwillbeconcentricwiththeaxisofrotationofthelathe.Thepositionoftheholecanbeaccuratelylocatedbyholdingtheworkpieceinthelathesothattheaxisaboutwhichtheholeistobemachinedcoincideswiththeaxisofrotationofthelathe.Whentheboringoperationisdoneinthesamesetupoftheworkthatisusedtoturnandfaceit,practicallyperfectconcentricityandperpendicularitycanbeachieved.Theboringtoolisheldinaboringbarwhichisfedthroughtheholebycarriage.Variationsofthisdesignareused,dependingonthejobtobedone.Theleadangleused,ifany,shouldalwaysbesmall.Also,thenoseradiusoftheboringtoolmustnotbetoolarge.Thecuttingspeedusedforboringcanbeequaltothespeedforturning.However,whenthespindlespeedofthelatheiscalculated,thefinished,orlargest,borediametershouldbeused.Thefeedrateforboringisusuallysomewhatlessthanforturningtocompensatefortherigidityoftheboringbar.Theboringoperationisgenerallyperformedintwosteps;namely,roughboringandfinishboring.Theobjectiveoftherough-boringoperationistoremovetheexcessmetalrapidlyandefficiently,andtheobjectiveofthefinish-boringoperationistoobtainthedesiredsize,surfacefinish,andlocationofthehole.Thesizeoftheholeisobtainedbyusingthetrial-cutprocedure.Thediameteroftheholecanbemeasuredwithinsidecalipersandoutsidemicrometercalipers.BasicMeasuringInstrument,orinsidemicrometercaliperscanbeusedtomeasurethediameterdirectly.Coredholesanddrilledholesaresometimeseccentricwithrespecttotherotationofthelathe.Whentheboringtoolentersthework,theboringbarwilltakeadeepercutononesideoftheholethanontheother,andwilldeflectmorewhentakingthisdeepercut,withtheresultthattheboredholewillnotbeconcentricwiththerotationofthework..Thiseffectiscorrectedbytakingseveralcutsthroughtheholeusingashallowdepthofcut.Eachsucceedingshallowcutcausestheresultingholetobemoreconcentricthanitwaswiththepreviouscut.Beforethefinale,finishcutistaken,theholeshouldbeconcentricwiththerotationoftheworkinordertomakecertainthatthefinishedholewillbeaccuratelylocated.Shoulders,grooves,contours,tapers,andthreadsarealsoboredinsideofholes.Internalgroovesarecutusingatoolthatissimilartoexternalgroovingtool.Theprocedureforboringinternalshoulderisverysimilartotheprocedureforturningshoulders.Largershouldersarefacedwiththeboringtoolpositionedwiththenoseleading,andusingthecrossslidetofeedthetool.Internalcontourscanbemachinedusingatracingattachmentonalathe.Thetracingattachmentismountedonthecrossslideandthestylusfollowstheoutlineofthemasterprofileplate.Thiscausesthecuttingtooltomoveinapathcorrespondingtotheprofileoftheprofileplate.Thus,theprofileonthemasterprofileplateisreproducedinsidethebore.Themasterprofileplateisaccuratelymountedonaspecialslidewhichcanbepreciselyintwodirections,inordertoalignthecuttingtoolinthecorrectrelationshiptothework.Thislathehascam-locktypeofspindlenosewhichpermitsittotakeacutwhenrotatingineitherdirection.Normalturningcutsaretakenwiththespindlerotatingcounterclockwise.Theboringcutistakenwiththespindlerevolvinginaclockwisedirection,or“backwards”.Thispermittheboringcuttobetakenonthe“backside”oftheborewhichiseasiertoseefromtheoperator’spositionfrontofthelathe.Thisshouldnotbedoneonlatheshavingathreadedspindlenosebecausethecuttingforcewilltendtounscrewthechuck.MillingMillingisamachiningprocessforremovingmaterialbyrelativemotionbetweenaworkpieceandarotatingcutterhavingmultiplecuttingedges.Insomeapplications,theworkpieceisheldstationarywhiletherotatingcutterismovedpastitandagivenfeedrate(traversed).Inotherapplications,boththeworkpieceandcutteraremovedinrelationtoeachotherandinrelationtothemillingmachine.Morefrequently,however,theworkpieceisadvancedatarelativelylowrateofmovementorfeedtoamillingcutterrotatingatacomparativelyhighspeed,withthecuteraxisremaininginafixedposition,acharacteristicfeatureofthemillingprocessisthateachmillingcuttertoothtakesitsshareofthestockintheformofsmallindividualchips.Millingoperationsareperformedonmanydifferentmachines.Sinceboththeworkpieceandcuttercanbemovedrelativetooneanother,independentlyorincombination,awidevarietyofoperationscanbeperformedbymilling.Applicationsincludetheproductionofflatorcontouredsurfaces,slots,grooves,recesses,threads,andotherconfigurations.Millingisoneofthemostuniversal,yetcomplicatedmachiningmethods.Theprocesshasmorevariationsinthekindsofmachinesused,workpiecemovements,andtypesoftoolingthananyotherbasicmachiningmethod.Importantadvantagesofremovingmaterialbymeansofmillingincludehighstockremovalrates,thecapabilityofproducingrelativelysmoothsurfacefinishes,andthewidevarietyifcuttingtoolsthatareavailable.Cuttingedgesofthetoolscanbeshapedtoformanycomplexsurface.Themajormillingmethodsareperipheralandfacemilling;inaddition,anumberofrelatedmethodsexistthatarevariationsofthesetwomethods,dependinguponthetypeofworkpieceorcutter.PeripheralMillingOnperipheralmilling,sometimescalledslabmilling,themilledsurfacegeneratedbyteethorinsertslocatedintheperipheryofthecutterbodyisgenerallyinaplaneparalleltothecutteraxis.Millingoperationswithform-relievedandformedprofilecuttersareincludedinthisclass.Thecrosssectionofthemilledsurfacecorrespondstotheoutlineorcontourofthemillingcutterorcombinationofcuttersused.Peripheralmillingoperationsareusuallyperformedonmillingmachineswiththespindlepositionedhorizontally,however,theycanalsobeperformedwithendmillsonvertiasl-spindlemachines.Themillingcuttersaremountedonanarborwhichisgenerallysupportedattheouterendforincreasedrigidity,particularlywhen,becauseoftheconditionsofthesetup,thecutterorcuttersareloca