【溫馨提示】====【1】設(shè)計(jì)包含CAD圖紙 和 DOC文檔，均可以在線預(yù)覽，所見(jiàn)即所得，，dwg后綴的文件為CAD圖，超高清，可編輯，無(wú)任何水印，，充值下載得到【資源目錄】里展示的所有文件======【2】若題目上備注三維，則表示文件里包含三維源文件，由于三維組成零件數(shù)量較多，為保證預(yù)覽的簡(jiǎn)潔性，店家將三維文件夾進(jìn)行了打包。三維預(yù)覽圖，均為店主電腦打開(kāi)軟件進(jìn)行截圖的，保證能夠打開(kāi)，下載后解壓即可。======【3】特價(jià)促銷，，拼團(tuán)購(gòu)買，，均有不同程度的打折優(yōu)惠，，詳情可咨詢QQ：1304139763 或者 414951605=====

中國(guó)地質(zhì)大學(xué)長(zhǎng)城學(xué)院 本科畢業(yè)設(shè)計(jì)外文資料翻譯 系 別： 工程技術(shù)系 專 業(yè)： 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 姓 名： 王碩 學(xué) 號(hào)： 05211611 2015年 4 月 4 日 1 機(jī)械設(shè)計(jì)制造及自動(dòng)化專業(yè)畢業(yè)設(shè)計(jì)（論文）外文翻譯 附錄一 Drilling and Milling Machines Upright drilling machines or drill presses are available in a variety of sizes and types, and are equipped with a sufficient range of apindle speeds and automatic feeds to fit the neds of most industries. Speed ranges on a typical machine are from 76 to 2025 rpm., with drill feed from 0.002 to 0.020 in.per revolution of the spindle. Radial drilling machines are used to drill workpieces that are too large or cumbersome to conveniently move. The spindle with the speed and feed changing mechanism is mounted on the radial arm; by combining the movement of the radial arm around column and the movement of the spindle assembly along the arm, it is possible to align the spindle and the drill to any position within reach of the machine. For work that is too large to conveniently support on the base, the spindle assembly can be swung out over the floor and the workpiece set on the beside the machine. Plain radial drilling machines provide only for vertical movement of the spindle; universal machines allow the spindle to swivel about an axis normal to the radial arm and the radial arm to rotate about a horizontal axis, thus permitting drilling at any angle. A multispindle drilling machine has one or more heads that drive the spindles through universal joints and telescoping splined shafts. All spindles are usually driven by the same motor and fed simultaneously to drill the desired number of holes. In most machines each spindle is held in an adjustable plate so that it can be moved relative to the others. The area covered by adjacent spindles overlap so that the machine can be set to drill holes at any location within its range. The milling operation involves metal removal with a rotating cutter. It includes removal of metal from the surface of a workspiece, enlarging holes, and form cutting, such as threads and gear teeth. Within an knee and column type of milling machine the column is the main supporting member for the other components, and includes the base containing the drive motor, the spindle, and the cutters. The cutter is mounted on an arbor held in the spindle, and supported on its outer extremity by a bearing in the overarm. The knee is held on the column in dovetail slots, the saddle is fastened to the knee in dovetail slots, and the table is attached to the saddle. Thus, the build-up the knee and column 2 機(jī)械設(shè)計(jì)制造及自動(dòng)化專業(yè)畢業(yè)設(shè)計(jì)（論文）外文翻譯 machine provides three motions relative to the cutter. A four motion may be provided by swiveling the table around a vertical axis provided on the saddle. Fixed-bed milling machines are designed to provide more rigidity than the knee and column type. The table is mounted directly on the machine base, which provides the rigidity necessary for absorbing heavy cutting load, and allows only longitudinal motion to the table. Vertical motion is obtained by moving the entire cutting head. Tracer milling is characterized by coordinated or synchronized movements of either the paths of the cutter and tracing elements, or the paths of the workpiece and model. In a typical tracer mill the tracing finger follow the shape of the master pattern, and the cutter heads duplicate the tracer motion. The following are general design considerations for milling: 1. Wherever possible, the part should be designed so that a maximum number of surfaces can be milled from one setting. 2. Design for the use of multiple cutters to mill several surfaces simultaneously. 3. The largest flat surface will be milled first, so that all dimensions are best referred to such surface. 4. Square inside corners are not possible, since the cutter rotates. Grinding Machines and Special Metal-removal Process Random point-cutting tools include abrasives in the shape of a wheel, bonded to a belt, a stick, or simply suspended in liquid. The grinding process is of extreme importance in production work for several reasons. 1.It is most common method for cutting hardened tool steel or other heat-treated steel. Parts are first machined in the un-heat-treated condition, and then ground to the desired dimensions and surface finish. 2.It can provide surface finish to 0.5μm without extreme cost. 3.The grinding operation can assure accurate dimensions in a relatively short time, since machines are built to provide motions in increments of ten-thousandths of an inch, instead of thousandths as is common in other machines. 4.Extremely small and thin parts can be finished by this method, since light pressure is used and the tendency for the part to deflect away from the cutter is minimized. On a cylindrical grinding machine the grinding wheel rotates between 5500 and 6500 rpm., while the work rotates between 60 and 125 rpm... The depth of cut is 1 3 機(jī)械設(shè)計(jì)制造及自動(dòng)化專業(yè)畢業(yè)設(shè)計(jì)（論文）外文翻譯 controlled by moving the wheel head, which includes both the wheel and its drive motor. Coolants are provided to reduce heat distortion and to remove chips and abrasive dust. Material removal from ductile materials can be accomplished by using a tool which is harder than the workpiece. However during Word War Ⅱ the widespread use of materials which were as hard or harder than cutting tools created a demand for new material-removal methods. Since then a number of processes have been developed which, although relatively slow and costly, can effectively remove excess material in a precise and repeatable fashion. There are two types of processes. The first type is based on electrical phenomena and is used primarily for hard materials; the second depends upon chemical dissolution. Chemical milling is controlled etching process using strong alkaline or acid etchants. Aluminum, titanium, magnesium, and steel are the principal metals processed by this method. The area to remain untouched by the etchant are masked with a protective coating. For example, the entire part may be dipped in the masking material and the mask removed from those areas to be etched, or a chemically resistant prescribed time, after which the part is rinsed in cold water, the masking removed, the part inspected, and thoroughly cleaned. There are certain disadvantages to consider. Metal will erode equally in all directions, so that walls of the etched section will have a radius equal to the depth of etch. A second disadvantage is that a better finish is obtained on surfaces parallel to the direction of rolling of a sheet than on surface perpendicular to the direction of rolling. This can be compared to the surface obtained when working wood parallel to, or across the grain. A third disadvantage, not unique with this process, is the warpage that will occur in thin, previously stressed sections etched on just one side. Chemical milling, however, has many advantages over conventional metal- removal methods. There is no warpage of heavy sections such as forgings or extrusions when the etchant is applied simultaneously to all sides for reduction of section thickness. In conventional milling only one side can be worked at a time, and frequent turning of a part is necessary to prevent warpage. Chemical milling can be applied to parts of irregular shape where conventional milling may be very difficult. Light-weight construction can be obtained with chemical milling by the elimination of welding, riveting, and stiffeners; parts can be contoured to distribute the load in the most suitable manner. As an example of the potential savings of this process, as compared to machine milling, one company reports that the cost of removing 1 4 機(jī)械設(shè)計(jì)制造及自動(dòng)化專業(yè)畢業(yè)設(shè)計(jì)（論文）外文翻譯 aluminum by chem.-milling is $0.27 per pound as compared to $1.00 per pound by conventional milling. The rate of metal removal for chem.-milling is 0.001in. for aluminum. Electric-discharge machining is a process in which an electrical potential is impressed between the workpiece and the tool, and the current, emanating from a point source on the workpoiece, flows to the tool in the form of a spark. The forces that accomplish the metal removal are within the workpiece proper and, as a result, it is not necessary to construct the unit to withstand the heavy pressures and loads prevalent with conventional machining methods. The frequency of the electrical discharge ranges from 20,00 cps (cycles per second) for rough machining, to 50,000 cps for finishing such items as hardened tools and dies. The current may vary from 50 amp, during rough machining, to as low as 0.5 amp, during finishing. The process is currently applied to the machining of single- point tools, form tools, milling cutters, broaches, and die cavities. It is also applicable to the removal of broken drills, taps, and studs without damaging the workpiece in which the broken tool is imbedded. Other uses are the machining of oil holes in a hardened part, and the machining of small safety-wire holes in the heads of special alloy bolts, such as titanium. The ultrasonic machining process is applied to both conducting and non- conducting material, and relies entirely upon abrasive action for metal removal. The workpiece is submerged in slurry of finely fivided abrasive particles in a vehicle such as water. The tool is coupled to an oscillator and vibrates at frequencies between 15,000 and 30,000 cps. The vibrating tool cavitates the liquid, and the force drives the abrasive into the surface of the workpiece to remove metal chips which are carried away by the liquid. The acceleration given the abrasive grains is as much as 100,000 times the acceleration of gravity, providing a smooth and rapid cutting force. Introduction of Machining Machining as a shape-producing method is the most universally used and the most important of all manufacturing processes. Machining is a shape-producing process in which a power-driven device causes material to be removed in chip form. Most machining is done with equipment that supports both the work piece and cutting tool although in some cases portable equipment is used with unsupported workpiece. Low setup cost for small quantities. Machining has tow applications in 1 5 機(jī)械設(shè)計(jì)制造及自動(dòng)化專業(yè)畢業(yè)設(shè)計(jì)（論文）外文翻譯 manufacturing. For casting, forging, and pressworking, each specific shape to be p5roduced, even one part, nearly always has a high tooling cost. The shapes that may be produced, even one part, nearly always has a high tooling cost. The shapes that may be produced by welding depend to a large degree on the shapes of raw material that are available. By making use of generally high cost equipment but without special tooling, it is possible, bu machining, to start with nearly any form of any material, so long as the exterior dimensions are great enough, and produce any desired shape from any material. Therefore, machining is usually the preferred method for producing one or a few parts, even when the design of the part would logically lead to casting, forging or pressworking if a high quantity were to be produced. Close accuracies, good finishes. The second application for machining is based on the high accuracies and surface finishes possible. Many of the parts machined in low quantities would be produced with lower but acceptable tolerances if produced in high quantities by some other process. On the other hand, many pars are given shapes by some high quantity deformation process and machined only on selected surfaces where high accuracies are needed. Internal threads, for example, are seldom produced by any means other than machining and small holes in pressworked parts may be machined following the pressworking operations. 1 6 機(jī)械設(shè)計(jì)制造及自動(dòng)化專業(yè)畢業(yè)設(shè)計(jì)（論文）外文翻譯 鉆床和銑削 直式鉆床或鉆孔式印刷機(jī)可用于各種尺寸和種類，它能安裝軸速度的 足夠范圍和自動(dòng)運(yùn)轉(zhuǎn)以適應(yīng)大多工業(yè)的要求。一個(gè)典型機(jī)器的速度范圍是70至 2025rmp，以及鉆孔的運(yùn)轉(zhuǎn)速度是0.002到0.020英尺。 旋轉(zhuǎn)鉆床用來(lái)鉆那些太大或太笨重的而不能夠移動(dòng)的工件。通過(guò)將轉(zhuǎn)臂 繞立柱的轉(zhuǎn)動(dòng)和主軸組件沿轉(zhuǎn)臂的移動(dòng)組合，可使主軸鉆頭對(duì)準(zhǔn)機(jī)床可達(dá)范圍 內(nèi)的任何位置，由于運(yùn)轉(zhuǎn)太大而不方便建立在此基礎(chǔ)上，主軸能夠在垂直的地 上方搖擺以及工件能固定在機(jī)器旁邊的地上。 普通的旋臂鉆床只提供軸的垂直運(yùn)動(dòng)和徑向轉(zhuǎn)臂，通過(guò) 軸來(lái)運(yùn)轉(zhuǎn)。 此 鉆頭 于任何一個(gè) 度。 一個(gè)多軸通過(guò) 能 和可 的 軸來(lái) 動(dòng)的鉆床 一個(gè)或多個(gè) 頭。通 的軸 是通過(guò) 的 動(dòng)機(jī)來(lái) 動(dòng)和 運(yùn)轉(zhuǎn)， 的是鉆 的 。 多鉆床的 個(gè)軸?￠在一個(gè)可￡?的￥?，以便§currency1' “的?件 移動(dòng)。 ?的軸重??fi的fl –? 的?使機(jī)器能夠在它的范圍的任何地方· 鉆孔。 ?床??§轉(zhuǎn)動(dòng)的?”?…和移動(dòng) “。它‰ ?一個(gè)工件的 `?… 移動(dòng)， 的′大和?型?”，?ˉ?和˙¨。 ? 機(jī)床的?? 式柱是currency1'?件的主要???fi?！??? 動(dòng)機(jī) 的基礎(chǔ)，ˇ軸?—工 。?—工 固定在?￠在主軸的 上能過(guò)一個(gè) 臂的軸 ? 在它的外?的 。?? 通過(guò) 動(dòng)? 立柱和立柱機(jī)器，提供一 種§?—工 “的 向。 一種 向可能是工? 由提供的 ?圍繞 軸旋轉(zhuǎn)而a到的。 固定的? 機(jī)床的設(shè)計(jì) 的是??? 或立柱提供 大的 度。工? 直 固定在機(jī) 的 ?，它能??大?—?o提供?度的 要。而 對(duì)工? 徑度的方向。垂直運(yùn)動(dòng)是通過(guò)移動(dòng)?個(gè)?—工 能達(dá)到。 型?床的 ?是 和 件的? 運(yùn)動(dòng)的 ￡或 ?，或?是 工件或?型的??運(yùn)動(dòng)的 ￡或 ?典型的 型?床的 型 是 ?型的 形式，而 ?—機(jī)頭?fi§ ?fi 。 下`是?”的總體的設(shè)計(jì) 錄： 1.ˉ果可能的話，零件將被設(shè)計(jì)以便在一個(gè)工位上最大的 `能被?”。 2.對(duì)選擇性的?—工 的設(shè)計(jì) 的是 ?”幾個(gè) `。 1 7 機(jī)械設(shè)計(jì)制造及自動(dòng)化專業(yè)畢業(yè)設(shè)計(jì)（論文）外文翻譯 3.應(yīng)當(dāng)首先?最大的 `，這樣 的尺寸 能 好的參 這個(gè) `。 4. ??—工 的轉(zhuǎn)動(dòng)， 形?的各個(gè) 落是不可能的。 刺耳的機(jī)器和特殊的金屬移動(dòng)程序 隨機(jī)??” ‰ 構(gòu)?¨子形狀的，或粘結(jié)到帶子或棍子上或直 浮 在液體 的研磨材料。 ?幾個(gè)原 研磨進(jìn)程在工件的生產(chǎn) 重要。 對(duì)?”硬化的 鋼材料或currency1'的熱 鋼材來(lái)講它是最普通的方法。零件 在沒(méi) 熱 條件下第一次機(jī)器?—，然后a到 的尺度和 `光潔度。 它能在沒(méi) 極限范疇 提供 `光潔度達(dá)0.5微米。 研磨??在 對(duì)較短的 間內(nèi)能確保精確的尺度， ?機(jī)器在??currency1它機(jī) 器的一般精度構(gòu)造 提供的動(dòng)態(tài)是 英尺增加?百fi之一的精度，而不是千fi 之一。 尤currency1是小而細(xì)的零件能用這個(gè)方法完?，由于輕壓力被使用和零件的柔韌 性 折射 的?”值是最小的。 研磨¨子在圓柱形的研磨機(jī)器上在5500和6500rmp之間轉(zhuǎn)動(dòng)，當(dāng)工件在60 和125rmp之間轉(zhuǎn)動(dòng) ，?”的深度運(yùn)動(dòng)由木頭控制，它‰ ?¨子和它的 動(dòng) 動(dòng)機(jī)。冷卻液用來(lái)?低熱扭曲和移動(dòng)?”以及研磨材料 的灰塵。 韌性的材料的運(yùn)動(dòng)通過(guò)那些材質(zhì)硬的 來(lái)完?，但是在二戰(zhàn)期間材料 的廣泛傳播使用，它?新材料運(yùn)動(dòng)方法的?” 的要求 高。 ?大 的過(guò)程 被改進(jìn)，盡管 當(dāng)慢 費(fèi)高，它能用精確 受的方式來(lái)移動(dòng)過(guò) 的材料，這 ? 兩種進(jìn)程?式：第一種類型是建立在電子現(xiàn)象的基礎(chǔ)上，它用于基本的原 材料 第二種 于化 。 化 質(zhì)的?”用于控制那些用? 的 性或 性的 進(jìn)程。 和鋼是通過(guò)這種方式的主要原料進(jìn)程?；??”· 于一個(gè)零件的傳 的 光潔，‰ 和 ，這個(gè) ?用以 ?不§那些 在制 外`的 ?？梢詫?個(gè)零件 材料，然后將 將要被 的–?? ￠ ￡可以使用?化 的粘 帶 要保￥的–?， 之后要 一般 ?定的 間，然后要將零件在冷§ currency1'，將 ?￠，“?零件，??fi fl`的currency1'。 應(yīng)–??到的·?：第一·?是?…在各個(gè)方` 是 的 ，以至 于 的外??徑和 的深度 第二個(gè)·?是在 于鋼?的方向上 a光潔度要?垂直于木?的方向上工? a的 ` ?較 第 個(gè)·?不是過(guò) 1 8 機(jī)械設(shè)計(jì)制造及自動(dòng)化專業(yè)畢業(yè)設(shè)計(jì)（論文）外文翻譯 程的?一，而是 生在細(xì)的只 一邊的壓力?上的”曲。 而化 ?”在傳 的?…移動(dòng)方 多的??。這在 多?件沒(méi) ”曲 …ˉ當(dāng) 被用來(lái)?低‰?` 度的各個(gè)`上 的?造和 壓，傳 的?”? 一次只用一`來(lái)運(yùn)轉(zhuǎn)，而 零件的`′轉(zhuǎn)?是?ˉ”曲 ?要的?；??”能用 于不˙¨的?件，而那是傳 ?” ?到的。輕?的建 可通過(guò)? 的currency1￠ ? 和加?ˇ§?”而—a零件可以被定形通過(guò)以適當(dāng)?shù)姆绞絝i ?o和 在 的 過(guò)程的…子一樣，§機(jī)器?—?床 ?。一個(gè)文件 ? “化 ?”移 動(dòng) 的?本，是0.2 英 ，而傳 ?”¨是1.00 英 。 以?” ?…移動(dòng)的? 是0.001英尺 fi 。 電子 機(jī)器是一個(gè)電壓?用于工件和 之間的過(guò)程，電 ?…工件 的 頭 ，以 的形式 向 。完??…移動(dòng)的力 是?…工件本 。結(jié) 果，對(duì)一般的傳 機(jī)械??而 ，沒(méi) ?要建設(shè)一個(gè)a 來(lái) 制重壓和重?o。 由于 器的范圍大 2000 p 至5000 p 用來(lái)精加工ˉ此硬的 和? 。 電 在?加工期間是不??化的。 50?mp低到精加工期間的0.5?mp，這個(gè)過(guò)程 應(yīng)用?機(jī)械的a? ，?形 ，?”?— ，o 以及? 。它￡能 移動(dòng) ?的鉆頭，而 和? 不 的工件。currency1'的使用方法是一個(gè)硬? 件的? ，小安fl電? 的機(jī)械是由大 合?制造的，ˉ 。 ?機(jī)械程?用于?體和??體，而 完fl? 于?…移動(dòng)的研磨 ?， 工件 沒(méi)在液下fi 的研磨微 ˉ§。 蕩器以及在15000至 3000 p 之間`′的 動(dòng)， 動(dòng)的 抽空液體，沖力研磨材料進(jìn) 工件的 `用來(lái)移動(dòng)?…?”。它們能隨 液體 動(dòng)。研磨的?密加速度是重力的100000 倍，以提供一個(gè)光 而快速的?”沖力。 關(guān)于機(jī)械加工 ??一種?形方式的機(jī)械加工是廣泛使用的￡是 機(jī)械制造進(jìn)程 的最 重要的?fi。機(jī)械加工是通過(guò)?”形式使 動(dòng)裝置引起材料運(yùn)動(dòng)產(chǎn)生形狀的過(guò)程 盡管在某些場(chǎng)合，工???情況下，使用移動(dòng)式裝備實(shí)現(xiàn)加工，但是大多 的 機(jī)械加工 是通過(guò)既? 工件 ? 的裝備來(lái)完?。 小批 生產(chǎn)低費(fèi)用，機(jī)械加工在制造方` 兩種用途：對(duì)澆 ，?造，壓 力加工，即將生產(chǎn)的 個(gè) 體形狀，甚至一個(gè)零件而 ，幾乎是一個(gè)高標(biāo)準(zhǔn)的 鑄型。這些通過(guò)? 可能產(chǎn)生的形狀在 大程度上 可利用的原材料的形 狀。一般說(shuō)來(lái)，通過(guò)利用高價(jià)設(shè)備而又無(wú) 種加工條件下，幾乎可以 任何種 類原材料· ，借助機(jī)械加工把原材料加工?任 要求的結(jié)構(gòu)形狀，只要外? 尺寸夠大，那 是可能的。 此，機(jī)械加工是 用來(lái)生產(chǎn)少 零件，甚至在大 生產(chǎn)以及當(dāng)零件的設(shè)計(jì)在邏輯上?致澆鑄 ?造，壓力加工的 候 推薦的方法 嚴(yán)密的精度，合適的 `?糙度，對(duì)機(jī)械加工的第二個(gè)應(yīng)用是建立在可 性的高精度和高 `?糙度之上。 多用機(jī)械?—的少 ?件會(huì)產(chǎn)生較小 能夠 1 9 機(jī)械設(shè)計(jì)制造及自動(dòng)化專業(yè)畢業(yè)設(shè)計(jì)（論文）外文翻譯 受的偏差是否能夠通過(guò)currency1'的工藝 程生產(chǎn)大 的?件。 一方`， 多?件 通過(guò)一些大 的?形過(guò)程和由機(jī)械?— 要的高精度選擇 ` ?'們的一 般形狀，…ˉ：內(nèi)?的?? 少能通過(guò)currency1'的方式生產(chǎn)，￠?機(jī)械加工和壓力 加工?件的小 可能被機(jī)器?—?的壓力加工過(guò)的??。 附錄二 LATHES & MILLING A shop that is equipped with a milling machine and an engine lathe can machine almost any type of product of suitable size. The basic machines that are designed primarily to do turning，facing and boring are called lathes. Very little turning is done on other types of machine tools，and none can do it with equal facility. Because lathe can do 1 10 機(jī)械設(shè)計(jì)制造及自動(dòng)化專業(yè)畢業(yè)設(shè)計(jì)（論文）外文翻譯 boring，facing，drilling，and reaming in addition to turning，their versatility permits several operations to be performed with a single setup of the workpiece. This accounts for the fact that lathes of various types are more widely used in manufacturing than any other machine tool. Lathes in various forms have existed for more than two thousand years. Modern lathes date from about 1797，when Henry Maudsley developed one with a leads crew. It provided controlled ， mechanical feed of the tool. This ingenious Englishman also developed a change gear system that could connect the motions of the spindle and leadscrew and thus enable threads to be cut. Lathe Construction. The essential components of a lathe are depicted in the block diagram of picture. These are the bed，headstock assembly，tailstock assembly，carriage assembly，quick-change gearbox，and the leadscrew and feed rod. The bed is the back bone of a lathe. It usually is made of well-normalized or aged gray or nodular cast iron and provides a heavy，rigid frame on which all the other basic components are mounted. Two sets of parallel，longitudinal ways，inner and outer，are contained on the bed，usually on the upper side. Some makers use an inverted V-shape for all four ways，whereas others utilize one inverted V and one flat way in one or both sets. Because several other components are mounted and/or move on the ways they must be made with precision to assure accuracy of alignment. Similarly，proper precaution should betaken in operating a lathe to assure that the ways are not damaged. Any inaccuracy in them usually means that the accuracy of the entire lathe is destroyed. The ways on most modern lathes are surface hardened to offer greater resistance to wear and abrasion. The headstock is mounted in a fixed position on the inner ways at one end of the lathe bed. It provides a powered means of rotating the work at various speeds. It consists，essentially，of a hollow spindle，mounted in accurate bearings，and a set of transmission gears——similar to a truck transmission——through which the spindle can be rotated at a number of speeds. Most lathes provide from eight to 1 11 機(jī)械設(shè)計(jì)制造及自動(dòng)化專業(yè)畢業(yè)設(shè)計(jì)（論文）外文翻譯 eighteen speeds，usually in a geometric ratio，and on modern lathes all the speeds can be obtained merely by moving from two to four levers. An increasing trend is to provide a continuously variable speed range through electrical or mechanical drives. Because the accuracy of a lathe is greatly dependent on the spindle，it is of heavy construction and mounted in heavy bearings，usually preloaded tapered roller or ball types. A long- itudinal hole extends through the spindle so that long bar stock can be fed through it. The size of this hole is an important size dimension of a lathe because it determines the maximum size of bar stock that can be machined when the material must be fed through the spindle. The inner end of the spindle protrudes from the gear box and contains a means for mounting various types of chucks，face plates，and dog plates on it. Whereas small lathes often employ a threaded section to which the chucks are screwed，most large lathes utilize either cam-lock or key-drive taper noses. These provide a large- diameter taper that assures the accurate alignment of the chuck，and a mechanism that permits the chuck or face plate to be locked or unlocked in position without the necessity of having to rotate these heavy attachments. Power is supplied to the spindle by means of an electric motor through a V-belt or silent-chain drive. Most modern lathes have motors of from 5 to15 horsepower to provide adequate power for carbide and ceramic tools at their high cutting speeds. The tailstock assembly consists，essentially，of three parts. A lower casting fits on the inner ways of the bed and can slide longitudinally thereon，with a means for clamping the entire assembly in any desired location. An upper casting fits on the lower one and can be moved transversely upon it on some type of keyed ways. This transverse motion permits aligning the tailstock and headstock spindles and provides a method of turning tapers. The third major component of the assembly is the tailstock quill. This is a hollow steel cylinder，usually about2 to3 inches in diameter，that can be moved several inches longitudinally in and out of the upper casting by means of a hand wheel and screw. The open end of the quill hole terminates in a Morse taper in 1 12 機(jī)械設(shè)計(jì)制造及自動(dòng)化專業(yè)畢業(yè)設(shè)計(jì)（論文）外文翻譯 which a lathe center，or various tools such as drills，can be held. A graduated scale，several inches in length，usually is engraved on the outside of the quill t