中英文翻译(3)

1、英文翻译原文 :(一 )BORING AND BORING MACHINESAs carried out on a lathe, boring produces circular internal profiles in hollow work-pieces or on a hole made by drilling or another process, Boring is done with cutting tools that are similar to those used in turning. Because the boring bar has to reach the ful

2、l length of the bore, tool deflection and, therefore, maintainance of dimensional accuracy can be a significant problem.The boring bar must be sufficiently stiff that is, made of a material with high elastic modulus, such as tun gste n carbido mini mize deflect ion and avoid vibrati on and chatter.

3、Boring bars have been designed with capabilities for damping vibration.Although boring operations on relatively small work-pieces. Can be carried out on a lathe, boring mills are used for large work-pieces. These machines are either vertical or horizontal, and are capable of performing operations su

4、ch as turning, facing, grooving, and chamfering. A vertical boring machine is similar to a lathe but has a vertical axis of work-piece rotation.The cutting tool (usually a single point made of M-2 and M-3 high-speed steel and C-7 and C-8 carbide) is mounted on the tool head, which is capable of vert

5、ical movement (for boring and turning) and radial movement (for facing), guided by the cross-rail. The head can be swiveled to produce conical (tapered) surfaces.In horizontal boring machine, the work-piece is mounted on a table that can move horizontally in both the axial and radial directions. The

6、 cutting tool is mounted on a spindle that rotates in the headstock, which is capable of both vertical and longitudinal movements. Drills, reamer, taps, and milling cutters can also be mounted on the machine spindle.Boring machine are available with a variety of features. Although work-piece diamete

7、rs are generally 1 m-4 m(3ft-12ft),work-piece as large as 20 m(60ft) can be machined in some vertical boring machines. Machine capacities range up to 150 kw (200hp).these machines are also available with computer numerical controls, which allow all movements to be programmed. With such controls, lit

8、tle operaror involvement is required and consistency and productivity are improved. Cutting speeds and feeds for boring are similar to those for turning.(For capabilities of boring operations)Jig borers are vertical boring machines with high -precision bearings. Although they are available in variou

9、s sizes and used in tool rooms for making jigs and fixtures, they are now being replaced by more versatile numerical control machines.Design considerations for boring. Guidelines for efficient and economical boring operations are similar to those for turning. Additionally, the following factors shou

10、ld be considered：a. Whenever possible, through holes rather than blind holes should be specified.(The term blind hole refers to a hole that does not go though the thickness of the work-piece )b. The greater the len gtho -bore-diameter ratio, the more difficult it is to hold dimensions because of the

11、 deflections of the boring bar due to cutting forces.c. Interrupted internal surfaces should be avoided.(2) Fundamentals of Machine ToolsIn many cases products form the primary forming processes must undergo further refinements in size and surface finish to meet their design specifications. To meet

12、such precise tolerances the removal of small amounts of material is needed. Usually machine tools are used for such operation.In the United States material removal is a big business-in excess of $ per year, including material, labor, overhead, and machine-tool shipments, is spent. Since 60 percent o

13、f the mechanical and industrial engineering and technology graduates have something connection with the machining industry either through sale, design, or operation of machine shops, or working in related industry, it is wise for an engineering student to devote some time in his curriculum to studyi

14、ng material removal and machine tools.A machine tool provides the means for cutting tools to shape a workpiece to required dimensions; the machine supports the tool and the workpiece in a controlled relationship through the functioning of its basic members, which are as follow:(a) Bed, Structure or

15、Frame. This is the main member which provides a basis for, and a connection between, the spindles and slides; the distortion and vibration under load must be kept to a minimum.(b) Slides and Sideways. The translation of a machine element (e.g. the slide) is normally achieved by straight-line motion

16、under the constraint of accurate guiding surfaces (the slideway).(c) Spindles and Bearings. Angular displacements take place about an axis of rotation; the position of this axis must be constant within extremely fine limits in machine tools, and is ensured by the provision of precision spindles and

17、bearings.(d) Power Unit. The electric motor is the universally adopted power unit for machine tools. By suitably positioning individual motors, belt and gear transmissions are reduced to a minimum.(e) Transmission Linkage. Linkage is the general term used to denote the mechanical, hydraulic, pneumat

18、ic or electric mechanisms which connect angular and linear displacements in defined relationship.There are two broad divisions of machining operations:(a) Roughing, for which the metal removal rate, and consequently the cutting force, is high ,but the required dimensional accuracy relatively low .(b

19、) Finishing, for which the metal removal rate, and consequently the cutting force, is low, but the required dimensional accuracy and surface finish relatively high .It follows that static loads and dynamic loads, such as result form an unbalanced grindingwheel, are more significant in finishing oper

20、ations than in roughing operations, The degree of precision achieved in any machining process will usually be influenced by the magnitude of the deflections, which occur as a result of the force acting.Machine tool frames are generally made in cast iron, although some may be steel casting or mild-st

21、eel fabrications. Cast iron is chosen because of its cheapness, rigidity, compressive strength and capacity for damping the vibrations set-up in machine operations, To avoid massive sections in castings, carefully designed systems of ribbing are used to offer the maximum resistance to bending and to

22、rsional stresses. Two basic types of ribbing are box and diagonal. The box formation is convenient to produce, apertures in walls permitting the positioning and extraction of cores. Diagonal ribbing provides greater torsional stiffness and yet permits swarf to fall between the sections; it is freque

23、ntly used for lathe beds.The slides and slideways of a machine tool locate and guide members which move relative to each other, usually changing the position of the tool relative to workpiece .The movement generally takes the form of translation in a straight line, but is sometimes angular rotation,

24、 e.g. tilting the wheel-head of a universal thread-grinding machine to an angle corresponding which the helix angle of the workpiece thread. The basic geometric elements of slides are flat, vee, dovetail and cylinder. These elements may be used separately or combined in various ways according to the

25、 applications . Features of slideways are as follows :(a) Accuracy of Movement. Where a slide is to be displaced in a straight line, this line must lie in two mutually perpendicular planes and there must be no slide rotation. The general tolerance for straightness of machine tool slideways is 00.02m

26、m per 1000mm; on horizontal surfaces this tolerance may be disposed so that a convex surface results, thus countering the effect of sag of the slideway.(b) Means of Adjustment. To facilitate assembly, maintain accuracy and eliminate play between sliding members after wear has taken place, a strip is

27、 sometimes inserted in slides. This is called a gibstrip. Usually, the gib is retained by socket-head screws passing through elongated slot；s and is adjusted by grub-screws secured by lock nuts.(c) Lubrication. Slideways may be lubricated by either of the following systems：1) Intermittently through

28、grease or oil nipples, a method suitable where movements are infrequent and speed low2) Continuously e.g. by pumping through a metering valve and pipe-work to the point of application; the film of oil introduced between surfaces by these means must be extremely thin to avoid the slide“If sflloidaitn

29、inggsurf”aces were optically flat oil would be squeezed out， resulting in the surfaces sticking. Hence in practice slide Sillfaces are either grourld using the edge of a cup whee，l or scraped. Both processes produee minulte surface depressions， which retain pocokfetoi”l, and complete separation of t

30、he parts may not occur at all points.(d) Protection To maintain slideways in good order, the following conditions must be met：1) Ingress of foreign matter， e g swarf， must be prevented. Where this is no possible，it is desirable to have a form of slideway，which does not retain swarf，e.g. the inverted

31、 vee.2) Lubricating oil must be retained The adhesive property of oil for use on vertical or inclined slide surface is important; oils are available which have been specially developed for this purpose. The adhesivenessof oil also preverts it being washed away by cutting fluids3) Accidental damage m

32、ust be prevented by protective guards译文:(一)镗削加工和镗床 像车床加工零件一样，镗床能在中空的工件或由钻削加工或其它工艺所加工 的孔上进行内轮廓圆的加工。镗削是由那些类似车削的刀具完成的。 因为镗头必 须达到镗杆的全长，刀具将发生弯曲，因此，尺寸精度的保持性成为了一个重大 问题。镗杆必须有足够的刚度刀杆是由较高弹性模量的材料制造的， 比如碳化 钨(硬质合金)去减小弯曲和避免摇动和振动。镗杆被设计有减振的能力。镗床既能加工在车床上加工的较小工件， 镗铣床又能加工巨大的工件。这类 机械既有立式的又有卧式的并且能够完成如：车削、车端面、切槽、和倒角。一 台立

33、式的镗床类似一台车床，但它有一根垂直的工件旋转轴。刀具(通常用于切削的单独切削点是由 M-2 和 M-3 高速钢和 C-8 硬质合金 制造的)被安装于能垂直运动(用于镗削和车削)和径向运动(用于车端面)并 由十字导轨导向的刀头上。刀头能够旋转去加工圆锥形表面。在卧式镗床上工件被装夹在能在水平面内两个轴向和径向上移动的工作台 上，刀具被安装于能做垂直和纵向两方向上运动的主轴箱上。钻头、铰刀、螺纹 刀和铣刀都能安装于机床主轴上。镗床具有许多优良的性能，它所加工工件的直径是 1m-4m(3ft-12ft) ，工件尺寸达到20m(60ft)的可在专用的立式镗床上加工。机床功率范围可达到150kw(20

34、0hp)。这些可用于所有运动都能编程的数字控制加工。利用这些控制，只需要很少的相关操作，并且稳定性和生产率大大提高了。镗床的切削速度和进 给速度和车床比较相似。坐标镗床是属于具有较高精度支撑的立式镗床。 尽管它们可用于各类尺寸的工件加工和拥有夹紧合安装的刀具空间。它们正被多功能的数控机床取代。 镗床的设计要求：导轨的效率，类似于车削的经济型操作，另外，应该考虑 以下因素：a. 无论何时，应尽可能注意是加工通孔而并盲孔。（盲孔系列是指那些没有穿国工件厚度的孔）b. 应该控制径向进给速率，很难去支撑径向，因为切削力引起镗杆的弯曲变 形。c. 应该避免交叉的内表面加工。（2）机床基础为了满足规定的设

35、计规格， 大多数情况下初步加工的产品都必须再经过进一 步的尺寸和表面的精加工。 要达到这样的精确规定公差的要求， 少量材料需要被 切除掉，而机床通常就是用于此种操作。在美国，材料切除是一项大业务一一每年这方面的支出超过36 x 109美元，包括材料、劳力和机床运输。 60%的机械工程和工业工程毕业生都通过贸易、设 计、机械修理工厂， 或通过在相关行业工作而与机械工业密不可分， 因而如果他 们花费一定的时间精力来学习这个领域中的材料切除和机床技术的话会是很明 智的选择。机床提供切割工具的方式，以使工件成型，达到规定的尺寸；此种机器依靠 其基础部件的运作来掌握工具和工件之间的联系。其基础部件的运作如下： 床身、构造和框架。这三种主要的部件为锭子和滑移的基础，并将它们联系起来；操作中的变形和震动必须尽量避免。 滑移与滑轨。机械部件（如滑移）的转换通常是通过在精密的指导表面（滑轨）的控制下做直线运动而完成的。 锭子与轴承。角位移是围绕一个旋转轴线发生的；这个转轴的位置必须一直处于严格精确的限制之中，并由精密锭子和轴承提供保障。 动力仪器。电动机是被广泛应用于机床的动