机械加工外文翻译、中英文翻译、机械类外文文献翻译

外文原文： Machining Turning The engine lathe, one of the oldest metal removal machines, has a number of useful and highly desirable attributes. Today these lathes are used primarily in small shops where smaller quantities rather than large production runs are encountered. The engine lathe has been replaced in todays production shops by a wide variety of automatic lathes such as automatic tracer lathes, turret lathes, and automatic screw machines. All the advantages of single-point tooling for maximum metal removal, and the use of form tools for finished on a par with the fastest processing equipment on the scene today. Tolerances for the engine lathe depend primarily on the skill of the operator. The design engineer must be careful in using tolerances of an experimental part that has been produced on the engine lathe by a skilled operator. In redesigning an experimental part for production, economical tolerances should be used. Turret Lathes Production machining equipment must be evaluated now, more than ever before, in terms of ability to repeat accurately and rapidly. Applying this criterion for establishing the production qualification of a specific method, the turret lathe merits a high rating. In designing for low quantities such as 100 or 200 parts, it is most economical to use the turret lathe. In achieving the optimum tolerances possible on the turret lathe, the designer should strive for a minimum of operations. Automatic Screw Machines Generally, automatic screw machines fall into several categories； single-spindle automatics, multiple-spindle rapid, automatic chucking machines. Originally designed for rapid, automatic production of screws and similar threaded parts, the narrow field, and today plays a vital role in the mass production of a variety of precision parts. Quantities play an important part in the economy of the parts machined on the automatic screw machine. The cost of the parts machined can be reduced if the minimum economical lot size is calculated and the proper machine is selected for these quantities. Automatic Tracer Lathes Since surface roughness depends greatly upon material turned, tooling, and feeds and speeds employed, minimum tolerances that can be held on automatic tracer lathes are not necessarily the most economical tolerances. In some cases, tolerances of 0.05mm are held in continuous production using but one cut. Groove width can be held to 0.0125mm on some parts. Bores and single-point finishes can be held to 0.0125mm. On high-production runs where maximum output is desirable, a minimum tolerance of 0.125mm is economical on both diameter and length of turn. Milling With the exceptions of turning and drilling, milling is undoubtedly the most widely used method of removing metal. Well suited and readily adapted to the economical production of any quantity of parts, the almost unlimited versatility of milling process merits the attention and consideration of designers seriously with the manufacture of their product. As in any other process, parts that have to be milled should be designed with economical tolerances that can be achieved in production mill. If the part is designed with tolerances finer than necessary, additional operations will have to be added to achieve these tolerances-and this will increase the cost of the part. Grinding Grinding is one of the most widely used methods of finishing parts to extremely close tolerances and fine surface finishes. Currently, there are grinders for almost every type of grinding machine required. Where processing costs are excessive, parts redesigned to worthwhile. For example, wherever possible the production economy of centerless grinding should be taken advantage of by proper design consideration. Although grinding is usually considered a finishing operation, it is often employed as a complete machining process on work which can be ground down from rough condition without being turned or otherwise machined. Thus many types of forgings and other parts are finished completely with the grinding wheel at appreciable savings of time and expense. Classes of grinding machines include the following: cylindrical grinders, centerless grinders, internal grinders, surface grinders, and tool expense. The cylindrical and centerless grinders or taper work； thus splines, shafts, and similar parts are ground on cylindrical machines either of the common-center type or the centerless machine. Thread grinders are used for grinding precision threads for thread gages, and threads on precision parts where the concentricity between the diameter of the shaft and pitch diameter of thread must be held to close tolerances. The internal grinders are used for grinding of precision holes, cylinder bores, and similar operations where bores of all kinds are to be finished. The surface grinders are for finishing all kinds of flat work, or work with plain surfaces which may be operated upon either by the edge of a wheel or by the face of a grinding wheel. These machines may have reciprocating or rotating tables. 译文： 机械加工 金属切削机床中最早的一种是普通车床，当今仍有许多 有用的特性。可是目前，这些机床主要用在较小规模的工厂中，进行较小规模的生产，而不用做大批量的生产。 当前的生产车间中，种类繁多的自动车床已经取代了普通车床。比如自动仿形车床，六角车床和自动螺丝车床。现今，设计人员已经熟习的知道了先用单刃刀具去除大量的金属余量，后用成型刀具获得精度和表面粗糙度这种加工方法的优点。它的生产速度和现在工厂中使用的最快的加工设备相等。 操作者的技术熟练程度是影响普通车床加工偏差的重要因素。设计工程师要认真的确定由熟练工人在普通车床上加工的试验零件的公差。在把试验零件做为生产零件时， 应选用比较经济的公差。 六角车床 从生产加工设备这方面看，现在比以往更着重评价是否具有精度和快速加工的能力。评价具体的加工方法用这个标准，六角车床可以获得较高的质量评定。 在设计小批量的零件加工方法时，最经济的是采用六角车床。同时，为了获得最小的公差，设计人员应尽最大限度的减小加工工序的数目。 自动螺丝车床 通常的它的类型可分为以下几种；单轴自动、多轴自动和自动夹紧车床。它最初是被用来对螺钉和类似带有螺纹的零件进行自动加工的。可是，此种车床的用处已经早就超出了这个范围。如今，在很多种类精密零件的大批量生产中 它起着重要的作用。所加工零件的数量，用自动螺丝车床对它的经济性有较大的影响。若工件的数量少于是 1000 件，六角车床上加工要比自动螺丝车床上加工经济的多。若算出最小经济批量，并且针对工件批量正确地选择机床，零件的加工成本就会自然的降低。 自动仿形车床 因为零件的表面粗糙度主要是取决于件材料、刀具、进给量、和切削速度，所以用自动仿形车床加工所得到的最小公差不一定是最经济的公差。 如在一些情况下，连续生产的过程中，只进行一次切削加工时的公差可以达到 0.05mm。对一些零件，槽宽的公差 0.125mm。采用单刃 刀具和镗孔进行精加工时，公差可达到 0.0125mm。在希望得到的产量的大批量生产中，直径和长度上的切削时的最小公差值为 0.125mm 是经济的。 铣削 把车削和钻削除外，应用最广泛的金属切削方法就是铣削。它很适合用在任何数量的零件的经济生