【正文】 對(duì)于某些零件，槽寬的公差可以達(dá)到 。自動(dòng)螺絲車床最初是被用來(lái)對(duì)螺釘和類似的帶有螺紋的零件進(jìn)行自動(dòng)化和快速加工的。 普通車床的加偏差主要信賴于操作者的技術(shù)熟練程度。計(jì)算機(jī)數(shù)控解決了主計(jì)算機(jī)發(fā)生故障所帶來(lái)的問(wèn)題，但是它產(chǎn)生了另一個(gè)被稱為數(shù)據(jù)管理的問(wèn)題。然而，它敢有著同其他信賴于主計(jì)算機(jī)技術(shù)一樣的局限性。即使對(duì)指令程序進(jìn)行最微小的調(diào)整，也必須中斷加工，制作一條新帶。因此，這個(gè)問(wèn)題變得很嚴(yán)重。最初的數(shù)控系統(tǒng)下今天應(yīng)用的數(shù)控系統(tǒng)是有很大差別的。數(shù)控這個(gè)概念是50 年代初在美國(guó)空軍的資助下提出來(lái)的。一個(gè)數(shù)控 技師的工作不是去操縱機(jī)床，而是編寫能夠發(fā)出機(jī)床操縱指令的程序。然而，操作工人的大部分時(shí)間卻花費(fèi)在簡(jiǎn)單的重復(fù)調(diào)整和觀察切屑 過(guò)程上。 普通車床是生產(chǎn)中最經(jīng)常使用的車床種類。它是一個(gè)直徑通常大約在 51~76mm（ 2~3英寸）之間的鋼制空心圓柱體。 由于機(jī)床的精度在很大程度上取決于主軸，因此，主軸的結(jié)構(gòu)尺寸較大，通常安裝在預(yù)緊后的重型圓錐滾子軸承或球軸承中。導(dǎo)軌上的任何誤差，常常意味著整個(gè)機(jī)床的精度遭到破壞。 車床的基本部件有：床身、主軸箱組件、尾座組件、溜板組件、絲杠和光杠。車削很少在其他種類的機(jī)床上進(jìn)行，而且任何一種其他機(jī)床都不能像車床那樣方便地進(jìn)行車削加工。有些制造廠對(duì)全部四條導(dǎo)軌都采用導(dǎo)軌尖朝上的三角形導(dǎo)軌（即山形導(dǎo)軌），而有的制造廠則在一組中或者兩組中都采用一個(gè)三角形導(dǎo)軌和一個(gè)矩形導(dǎo)軌。大多數(shù)車床有 8~12 種轉(zhuǎn)速，一般按等比級(jí)數(shù)排列。底板上有一個(gè)可以使整個(gè)尾座組件夾緊在任意位置上的裝置。它大約是兩頂尖連線與導(dǎo)軌上最近點(diǎn)之間距離的兩倍。 雖然普通車床有很多用途，是很有用的機(jī)床，但是更換和調(diào)整刀具以及測(cè)量工件花費(fèi)很多時(shí)間，所以它們不適合在大量生產(chǎn)中應(yīng)用。采用人工控制是，產(chǎn)品的質(zhì)量直接與操作者的技能有關(guān)。 一臺(tái)數(shù)控機(jī)床可以自動(dòng)生產(chǎn)很多 類的零件，每一個(gè)零件都可以有不同的和復(fù)雜的加工過(guò)程。 在這個(gè)問(wèn)題促使下，于 1959 年誕生了自 動(dòng)編程工具（ APT）語(yǔ)言。 一個(gè)主要問(wèn)題是穿孔紙帶的易損壞性。塑料帶的強(qiáng)度比紙帶的強(qiáng)度要高很多，這就可以解決常見(jiàn)的撕壞和斷裂問(wèn)題。操縱這些機(jī)床所需要的程序都存儲(chǔ)在這臺(tái)主計(jì)算機(jī)中 。采用 CNC 技術(shù)后，每臺(tái)機(jī)床上都有一個(gè)可編程邏輯控制器或者微機(jī)對(duì)其進(jìn)行數(shù)字控制。 在現(xiàn)代的生產(chǎn)車間中，普通車床已經(jīng)被種類繁多的自動(dòng)車床所取代，諸如自動(dòng)仿形車床，六角車床和自動(dòng)螺絲車床。 在為小批量的零件（ 100~200 件）設(shè)計(jì)加工方法時(shí)，采用六角車床是最經(jīng)濟(jì)的。如果計(jì)算出最小經(jīng)濟(jì)批量，并且針對(duì)工件批量正確地選擇機(jī)床，就會(huì)降低零件的加工成本。 附件 2：外文原文（復(fù)印件） Lathes Lathes are machine tools designed primarily to do turning, facing and boring, Very little turning is done on other types of machine tools, and none can do it with equal facility. Because lathes also can do drilling and reaming, their versatility permits several operations to be done with a single setup of the work piece. Consequently, more lathes of various types are used in manufacturing than any other machine tool. The essential ponents of a lathe are the bed, headstock assembly, tailstock assembly, and the leads crew and feed rod. The bed is the backbone of a lathe. It usually is made of well normalized or aged gray or nodular cast iron and provides s heavy, rigid frame on which all the other basic ponents 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 Vshape for all four ways, whereas others utilize one inverted V and one flat way in one or both sets, They are precisionmachined to assure accuracy of alignment. On most modern lathes the way are surfacehardened to resist wear and abrasion, but precaution should be taken 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 headstock is mounted in a foxed position on the inner ways, usually at the left end of the bed. It provides a powered means of rotating the word at various speeds . Essentially, it consists of a hollow spindle, mounted in accurate bearings, and a set of transmission gearssimilar to a truck transmission—through which the spindle can be rotated at a number of speeds. Most lathes provide from 8 to 18 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. The spindle has a hole extending through its length, through which long bar stock can be fed. The size of maximum size of bar stock that can be machined when the material must be fed through spindle. The tailsticd assembly consists, essentially, of three parts. A lower casting fits on the inner way