车床和车削外文文献翻译@机床类中英文翻译@外文翻译

英文材料 Lathe and Turning The Lathe and Its Construction A lathe is a machine tool used primarily for producing surfaces of revolution flat edges. Based on their purpose ,construction , number of tools that can simultaneously be mounted , and degree of automation ,lathes or, more accurately, lathe-type machine tools can be classified as follows: (1) Engine lathes (2) Toolroom lathes (3) Turret lathes (4) Vertical turning and boring mills (5) Automatic lathes (6) Special-purpose lathes In spite of that diversity of lathe-type machine tools, they all have all have common features with respect to construction and principle of operation .These features can best be illustrated by considering the commonly used representative type, the engine lathe. Following is a description of each of the main elements of an engine lathe , which is shown in Fig.11.1. Lathe bed . The lathe bed is the main frame , involving a horizontal beam on two vertical supporis. It is usually made of grey or nodular cast iron to damp vibrations and is made by casting . It has guideways to allow the carriage to slide easily lengthwise. The height of the lathe bed should be appropriate to enable the technician to do his or her jib easily and comfortably. Headstock. The headstock is fixed at the left hand side of the lathe bed and includes the spindle whose axis is parallel to the guideways (the silde surface of the bed) . The spindle is driven through the gearbox , which is housed within the headstock. The function of the gearbox is to provide a number of different spindle speeds (usually 6 up to 18 speeds) . Some modern lathes have headstocks with infinitely variable spindle speeds, which employ frictional , electrical , or hydraulic drives. The spindle is always hollow , I .e ,it has a through hole extending lengthwise. Bar stocks can be fed througth that hole if continous production is adopted . A lso , that hole has a tapered surface to allow mounting a plain lathe center . The outer surface of the spindle is 2 threaded to allow mounting of a chuck , a face plate , or the like . Tallstock . The tailstock assembly consists basically of three parts , its lower base, an intermediate part, and the quill . The lower base is a casting that can slide on the lathe bed along the guidewayes , and it has a clamping device to enable locking the entire tailstock at any desired location , depending upon the length of the workpiece . The intermediate parte is a casting that can be moved transversely to enable alignment of the axis of the the tailstock with that of the headstock . The third part, the quill, is a hardened steel tube, which can be moved longitudinally in and out of the intermediate part as required . This is achieved through the use of a handwheel and a screw , around which a nut fixed to the quill is can be locked at any point along its travel path by means of a clamping device. The carriage. The main function of the carriage is mounting of the cutting tools and generating longitudinal and /or cross feeds. It is actually an H-shaped block that slides on the lathe bed between the headstock and tailstock while being guided by the V-shaped guideways of the bed . The carriage can be moved either manually or mechanically by means of the apron and either the feed rod or the lead screw. When cutting screw threads, power is provided to the gearbox of the apron by the lead screw. In all other turning operations, it is the feed rod that drives the carriage. The lead screw goes through a pair o half nuts , which are fixed to the rear of the apron . When actuating a certain lever, the half nuts are clamped together and engage with the rotating lead screw as a single nut, which is fed , together with carriage, along the bed . when the lever is disengaged , the half nuts are released and the carriage stops. On the other hand , when the feed rod is used, it supplies power to the apron through a wrom gear . The latter is keyed to feed rod and travels with the apron along the feed rod , which has a keyway extending to cover its whole length. A modern lathe usually has a quick-change gearbox located under the headstock and driven from the spindle through a train of gears. It is connected to both the feed rod and the lead screw and enables selecting a variety of feeds easily and rapidly by simply shifting the appropriate levers, the quick-change gearbox is employed in plain turning, facing and thread cutting operations. Since that gearbox is linked to spindle, the distance that the apron (and the cutting tool) travels for each revolution of the spindle can be controlled and is referred to as the feed. Lathe Cutting Tools The shape and geometry of the lathe tools depend upon the purpose for which they are employed. Turning tools can be classified into tow main groups,namely,external cutting tools and internal cutting tools , Each of these groups include the following types of tools: 3 Turning tools. Turing tools can be either finishing or rough turning tools . Rough turning tools have small nose radii and are used for obtaining the final required dimensions with good surface finish by marking slight depth of cut . Rough turning tools can be right hand or left-hand types, depending upon the direction of feed. They can have straight, bent, or offset shanks. Facing tools . Facing tools are employed in facing operations for machining plane side or end surfaces. There are tools for machining left-hand-side surfaces and tools for right-hand-side surfaces. Those side surfaces are generated through the use of the cross feed, contrary to turning operations, where the usual longitudinal feed is used. Cutoff tools. Cutoff tools ,which are sometimes called parting tools, serve to separate the workpiece into parts and/or machine external annual grooves. Thread-cutting tools. Thread-cutting tools have either triangular, square, or tranpezoidal cutting edges, depending upon the cross section of the desired thread .Also , the plane angles of these tools must always be identical to those of the thread forms. Thread-cutting tools have straight shanks for external thread cutting and are of the bent-shank type when cutting internal threads . Form tools. Form tools have edges especially manufactured to take a certain form, which is opposite to the desired shape of the machined workpiece . An HSS tools is usually made in the form of a single piece ,contrary to cemented carbides or ceramic , which are made in the form of tipes. The latter are brazed or mechanically fastened to steel shanks. Fig.11.2 indicates an arrangement of this latter type, which includes the carbide tip , the chip breaker ,the pad ,the clamping screw (with a washer and a nut ) , and the shank. As the name suggests, the function of the chip breaker is to break long chips every now and then , thus preventing the formation of very long twisted ribbons that may cause problems during the machining operations . The carbide tips ( or ceramic tips ) can have different shapes, depending upon the machining operations for which they are to be employed . The tips can either be solid or with a central through hole ,depending on whether brazing or mechanical clamping is employed for mounting the tip on the shank. Lathe Operations In the following section , we discuss the various machining operations that can be performed on a conventional engine lathe. It must be borne in mind , however , that modern computerized numerically controlled lathes have more capabiblities and do other operations ,such as contouring , for example . Following are conventional lathe operations. Cylindrical turning . Cylindrical turning is the the simplest and the most common of 4 all lathe operations . A single full turn of the workpiece generate a circle whose center falls on the lathe axis； this motion is then reproduced numerous times as a result of the axial feed motion of the tool. The resulting machining marks are , therefore ,a helix having a very small pitch, which is equal to the feed . Consequently , the machined surface is always cylindrical. The axial feed is provided by the carriage or the compound rest , either manually or automatically, whereas the depths of cuts is controlled by the cross slide . In roughing cuts , it is recommended that large depths of cuts (up to 0.25 in. or 6 mm, depending upon the workpiece material) and smaller feeds would be used. On the other hand , very fine feeds, smaller depth of cut (less than 0.05in. , or 0.4 mm) , and high cutting speeds are preferred for finishing cuts. Facing . The result of a facing operation is a flat surface that is either the whole end surface of the workpiece or an annular intermediate surface like a shoulder . During a facing operation ,feed is provided by the cross slide, whereas the depth of cut is controlled by the carriage or compound rest . Facing can be carried out either from the periphery in ward or from the center of the workpiece outward . It is obvious that the machining marks in both cases tack the form of a spiral. Usually, it is preferred to clamp the carriage during a facing operation, since the cutting force tends to push the tool ( and , of course , the whole carriage ) away from the workpiece . In most facing operations , the workpiece is held in a chuck or on a face plate. Groove cutting. In cut-off and groove-cutting operations ,only cross feed of the tool is employed. The cut-off and grooving tools , which were previously discussed, are employed. Boring and internal turning . Boring and internal are performed on the internal surfaces by a boring bar or suitable internal workpiece is solid, a drilling operation must be performed first . The drilling tool is held in the tailstock, and latter is then fed against the workpiece. Taper turning . Taper turning is achieved by driving the tool in a direction that is not paralled to the lathe axis but inclined to it with an angle that is equal to the desired angle of the taper . Following are the different methods used in taper-turning practice: Rotating the disc of the compound rest with an angle to half the apex angle of the cone . Feed is manually provided by cranking the handle of the compound rest . This method is recommended for taper turning of external and internal surfaces when the taper angle is relatively large. Employing special form tools for external , very short ,conical surfaces . The width of 5 the workpiece must be slightly smaller than that of the tool ,and the workpiece is usually held in a chuck or clamped on a face plate . I n this case , only the cross feed is used during the machining process and the carriage is clamped to the machine bed . Offsetting the tailstock center . This method is employed for esternal tamper turning of long workpiece that are required to have small tamper angles (less than 8 ) . The workpiece is mounted between the two centers ； then the tailstock center is shifted a distance S in the direction normal to the lathe axis. Using the taper-turning attachment . This method is used for turning very long workpoece , when the length is larger than the whole stroke of the compound rest . The procedure followed in such cases involves complete disengagement of the cross slide from the carriage , which is then guided by the taper-turning attachment . During this process, the automatic axial feed can be used as usual . This method is recommend for very long workpiece with a small cone angle , i.e. , 8 through 10 . Thread cutting . When performing thread cutting , the axial feed must be kept at a constant rate , which is dependent upon the rotational speed (rpm) of the workpiece . The relationship between both is determined primarily by the desired pitch of the thread to be cut . As previously mentioned , the axial feed is automatically generated when cutting a thread by means of the lead screw , which drives the carriage . When the lead screw rotates a single revolution, the carriage travels a distance equal to the pitch of the lead screw rotates a single revolutional speed of the lead screw is equal to that of the spindle ( i. e . , that of the workpiece ), the pitch of the resulting cut thread is exactly to that of the lead screw . The pitch of the resulting thread being cut therefore always depends upon the ratio of the rotational speeds of the lead scew and the spindle : Pitch of the lead screw rpm of the workpiece = spindle-to-carriage gearing ratio Desired pitch of workpiece rpm of lead screw This equation is usefully in determining the kinematic linkage between the lathe spindle and the lead screw and enables proper selection of the gear train between them . n thread cutting operations , the workpiece can either be held in the chuck or mounted between the two lathe centers for relatively long workpiece . The form of the tool used must exactly coincide with the profile the thread to be cut , I . e . , triangular tools must be used for triangular threads , and so on . Knurling . knurling is mainly a forming operation in which no chips are prodyced . Tt involves pressing two hardened rolls with rough filelike surfaces against the rotating 6 workpiece to cause plastic deformation of the workpiece metal. Knurling is carried out to produce rough , cylindrical ( or concile )surfaces , which are usually used as handles . Sometimes , surfaces are knurled just for the sake of decoration ； there are different types of patterns of knurls from which to choose . Cutting Speeds and Feeds The cutting speed , which is usually given in surface feet per minute (SFM), is the number of feet traveled in circumferential direction by a given point on the surface (being cut ) of the workpiece in one minute . The relationship between the surface speed and rpm can be given by the following equation : SMF =3.14*DN Where D= the diameter of the workpiece in feet N=the rpm The surface cutting speed is dependent primarily upon the machined as well as the material of the cutting and can be obtained from handbooks , information provided by cutting tool manufacturera , and the like . generally , the SFM is taken as 100 when machining cold-rolled or mild steel ,as 50 when machining tougher metals , and as 200 when machining sofer materials . For aluminum ,the SFMis usually taken as 400 or above . There are also other variables that affect the optimal value of the surface cutting speed . These include the tool geometry, the type of lubricant or coolant , the feed , and the depth of cut . As soon as the cutting sped is decided upon , the rotational speed (rpm) of the spindle can be obtained as follows : SFM =3.14*D The selection of a suitable feed depends upon many factors , such as the required surface finish , the depth of cut , and the geometry of the tool used . Finer feeds produce better surface finish ,whereas higher feeds reduce the machining time during which the tool is in direct contact with the workpiece . Therefore ,it is generally recommended to use high feeds for roughing operations and finer feeds for finishing operations. Again, recommend values for feeds , which can be taken as guidelines , are found in handbooks and information booklets provided by cutting tool manufacturers. Here I want to introduce the drilling and milling : Drilling involves producing through or blind holes in a workpiece by forcing a tool , which rotates around its axis , against the workpiece .Consequently , the range of cutting from that axis of rotation is equal to the radius of the required hole .In practice , two symmetrical 7 cutting edges that rotate about the same axis are employed . Drilling operations can be carried out by using either hand drills or drilling machines . The latter differ in size and construction . nevertheless , the tool always rotates around its axis while the workpiece is kept firmly fixed . this is contrary to drilling on a lathe . Cutting Tool for Drilling Operations In drilling operations , a cylindrical rotary-end cutting , called a drill , is employed . The drill can have either one or more cutting edges and corresponding flutes , which can be straight or helical . the function of the flutes is to provide outlet passages for the chips generated during the drilling operation and to allow lubricants and coolants to reach the cutting edges and the surface being machined . Following is a survey of the commonly used drills. Twist drill . The twist drill is the most common type of drill .It has two cutting edges and two helical flutes that continue over the length of the drill body , as shown in Fig 12.1 The drill also consist of a neck and a shake that can be either straight or tapered .In the latter case , the shank is fitted by the wedge action into the tapered socket of the spindle and has a tang , which goes into a slot in the spindle socket ,thus acting as a solid means for transmitting rotation . On the other hand , straight shank drills are held in a drill chuck that is , in turn , fitted into the spindle socket in the same way as tapered shank drills. As can be seen in FIG.12.1 , the two cutting edges are referred to as the lips , and are connected together by a wedge , which is a chisel-like edge . The twist drill also has two margins , which enable proper guidance and locating of the drill while it is in operation . The tool point angle (TPA) is formed by the lips and is chosen based on the properties of the material to be cut . The usual TAP for commercial drills is 118 , which is appropriate for drilling low-carbon steels and cast irons . For harder and tougher metals , such as hardened steel , brasss and bronze , larger TPAs (130 OR 140 ) give better performance . The helix angle of the flutes of the commonly used twist drills ranges between 24 and 30 . When drilling copper or soft plastics , higher values for the helix angle are recommended (between 35 and 45). Twist drills are usually made of high speed steel ,although carbide tipped drills are also available . The size of twist drills used in industrial range from 0.01 up to 3.25 in . (i.e.0.25 up to 80 mm ) . Core drills . A core drill consists of the chamfer , body , neck ,and shank , as shown in Fig 12.2 . This type of drill may be have either three or four flutes and an equal number of margins , which ensure superior guidance , thus resulting in high machining accuracy . It can also be seen in Fig 12.2 that a core drill has flat end . The chamfer can have three or four cutting 8 edges or lips , and the lip angle may vary between 90 and 120 . Core drills are employed for enlarging previously made holes and not for originating holes . This type of drill is characterized by greater productivity , high machining accuracy , and superior quality of the drilled surfaces . Gun drills . Gun drills are used for drilling deep holes . All gun drills are straight fluted , and each has a single cutting edge . A hole in the body acts as a conduit to transmit coolant under considerable pressure to the tip of the drill . There are two kinds of gun drills , namely , the center cut gun drill used for drilling blind holes and the trepanning drill . The latter has a cylindrical groove at its center , thus generating a solid core , which guides the tool as it proceeds during the drilling operation. Spade drills . Spade drills are used for drilling large holes of 3.5 in .(90 mm ) or more . Their design results in a marked saving in cost of the tool as well as a tangible reduction in its weight , which facilitates its handling . moreover , this type of drill is easy to be ground . Milling and Milling Cutters Milling is a machining process that is carried out by means of a multiedge rotating tool known as a milling cutter . In this process ,metal removal is achieved through combining the rotary motion of the milling cutter and linear motions of the workpiece simultaneously . Milling operations are employed in producing flat , contoured and helical surfaces as well as for thread and gear and gear cutting operations. Each of the cutting edges of a milling cuter acts as an individual single point cutter when it engages with the workpiece metal . therefore , each of those cutting edges has the workpiece at a time ,heavy cuts can be taken without adversely affecting the tool life .In fact ,the permissible cutting speeds and feeds for milling are there to four times higher than those for turning or drilling .Moreover ,the quality of the surfaces machined by milling is generally superior of surfaces machined by turning shaping ,or drilling. A wide variety of milling cutters is available in industry .This, together with the fact that a milling machine is very versatile machine tool ,makes the milling machine the backbo ne of a machining workshop . As far as the direction of cutter rotation and workpiece feed are concerned , milling is performed by either of the following tow methods . Up milling (conventional milling). In up milling workpiece is fed against the direction of cutter rotation, as shown in Fig.12.3. As we can see in that figure ,the depth of cut (and consequently the load ) gradually increases on the successively engaged cutting edges . Therefore, the machining process involves no impact loading , thus ensuring smother operation 9 of the machine tool and longer tool life .The quality of the machined surface obtained by up milling is not very high . Nevertheless , up milling is commonly used in industry , especially for rough cuts. Down milling (climb milling ). Ascan be seen in Fig 12.3, in down milling the cutter rotation coincides with the direction of feed at the contact point between the tool and the workpiece . It can also be seen that the maximum depts. Of cut is achieved directly as the cutter engages with the workpiece . This results in a kind of impact , or sudden loading . Therefore, this method cannot be used the milling machine is equipped with a backlash elimination on the feed screw . The advantages of this method include higher quality of machined surface and easier clamping of workpieces, since the cutting forces act downward . Types of Milling Cutters There is a wide variety of milling cutter shapes .Each of them is designed to perform effectively a specific milling operations . Generally ,a milling cutter can be described as a multiedge cutting tool having the shape of a solid of revolution ,with the cutting teeth arranged either on the periphery or on an end face or on both . Following is a quick survery of the commonly used types of milling cutters. Plain milling cutter . a plain milling cutter is a disk shaped cutting tool that may have either straight or helical teeth ,as shown in Fig .12.4 .This type is always mounted on horizontal milling machines and is used for maching flat surfaces. Face milling cutter . A face milling cutter is also used for maching flat surfaces. It is bolted at the end of a short arbor ., which is in turn mounted on a vertical milling machine . Fig 12.4 indicates a milling cuter of this type. Plain metal slitting saw cutter .Fig 12.4 indicates a plain metal slitting saw cutter . We can see that it actually involves a very thin plain milling cutter. Side milling cutter. A side milling cutter is used for cutting solts, grooves, and splines. As shown in Fig 12.4 ,it is quite similar to the plain milling cutter , the difference being that this type has teeth on the sides .As is the case wih the plain cutter , the cutting teeth can be straight or helical . Angle milling cutter . Angle milling cutter is employed in cutting dovetail grooves , ratchet wheels, and the like .Fig 12.4 indicates a milling cutter of this type. T slot cutter . As shown in Fig 12.4 ,a T slot cutter involves a plain milling cutter with an integral shaft normal to it .As the name suggests ,this type is used for milling T slots. End mill cutter . End mill cutters find common applications in cutting slots , grooves , flutes , splines ,pocketing work, and the like . Fig 12.4 indicates an end mill cutter . The latter 10 is always mounted on a vertical milling machine and can have toe or four flutes , which may be either straight or helical . Form milling cutter . The teeth of a form milling cutter have a certain shape , which is identical to the section of the metal to be removed during the milling operation. Examples of this type include gear cutters ,gear hobs, convex and concave cutters ,and the like . Form milling cutters are mounted on horizontal milling machines. Materialas of Milling Cutters The commonly used milling cutters are made of high speed steel , which is generally adequate for most jobs . Milling cutters tipped with sintered carbides or cast nonferrous alloys as cutting teeth are usually employed for mass production , where heavier cuts and / or high cutting speeds are required. Here I want to introduce the Materials Types of Materials Materials may be grouped in several ways . scientists often classify materials by their state : solid , liquid , or gas . They also separate them into organic (once living) and inorganic (never living) materials. For industrial purposes , materials are divided into engineering materials or nonengineering materials .Engineering materials are those used in manufacture and become parts of products . Nonengineering materials are the chemicals ,fuels , lubricants ,and other materials used in the manufacturing process, which do not become part of the product. Engineering materials may be further subdivided into : 1 , Metals 2, Ceramics 3, Composite 4, Polymers , etc . Metals and Metals Alloys Metals are elements that generally have good electrical and thermal conductivity . Many metals have high strength , high stiffness , and have good ductility . Some metals ,such as iron ,cobalt and nickel , are magnetic . At extremely low temperatures , some metals and intermetallic compounds become superconductors. What is the difference between an alloy and a pure metal ? Pure metals are elements which come from a particular area of the periodic table . Examples of pure metals include copper in electrical wires and aluminum in cooking foil and beverage cans. Alloys contain more than one metallic element . Their properties can be changed by changing the elements present in the alloy . Examples of metal alloys include stainless steel which is an alloy of iron ,nickel ,and gold jewelry which usually contains an alloy of gold and nickel. Why are metals and alloys used ? Many metals have high densities and used in 11 applications which require a high mass to volume ratio. Some metal alloys , such as those based on aluminum , have low densities and are used in aerospace applications for fuel economy. Many alloys also have high fracture toughness, which means they can withstand impact and are durable. What are some important properties of metals? Density is defined as a material is a mass divided by its volume . Most metals have relatively high densities ,especially compared to polymers . Materials with high densities often contain atoms with high atomic numbers , such as gold or lead . However, some metals such as aluminum or magnesium have low densities ,and are used in applications that require other metallic proerties but also require low weight. Fracture toughness can be described as a materials ability to avoid fracture, especially when a flaw is introduced .Metals can generally contain nicks and dents without weakening very much ,and are impact resistant .A football player counts on this when he trusts that his facemask wont shatter. Plastic deformation is the ability of a material to bend or deform before breaking .As engineers , we usually design materials so that dont deform under normal conditions . You dont want you car to lean to the east after a strong west wind .However ,sometimes we can take advantage of plastic deformation. The crumple zones in a car absorb energy by undergoing plastic deformation before pass through. Alloy are compounds consisting of more than one metal one metal .Adding other metals can affect the density ,strength , fracture toughness , plastic deformation, electrical conductivity and environmental degradation .For example ,adding a small smount of iron to aluminum will make it stronger .Also , adding some chromium to steel will slow the rusting process, but will make it more brittle. 12 中文翻译 车床和车削 车床和它的结构 车床是一个主要用来生产旋转表面和平面的机床 . 基于他们的目的、结构，能同时装夹刀具的数量 ,车床或者 , 或更正确的说 , 车床 -类型的机床依下列各项被分类为 : (1) 普通车床 (2) 万能车床 (3) 转塔车床 (4) 立式的车削和钻孔机床 (5) 自动化车床 (6) 专用车床 尽管车床 -类型机床的多种多样，他们结构和工作的原则都有很大程度上的相似性。通过具有代表性的普通车床这些特征能最好地被说明 . 下列各项是对车床的主要元素的描述 ,如图 .11.1. 床身 . 车床的床身是主要的框架 ,包括在二个 垂直支撑架上的水平横梁 . 它通常由铸铁或者球墨铸铁通过铸造加工而成的用于防止振动 . 车床上的导轨让刀架容易地沿纵长滑动 . 车床床身的高度应该适中，这样使技术人员能够容易地而且舒适地做他或她的操作工作。 . 主轴箱 . 主轴箱安装在车床床身的左手边位置而且主轴与导轨 (床的滑动表面 )平行 . 主轴的驱动通过齿轮箱 ,齿轮箱安装在主轴箱中 . 齿轮箱的功能将提供一些不同的主轴转速 (通常由 6 到 18 速度 ) . 一些现代的车床具有无级调速的功能 , 由磨擦力、电 , 或液压的驱动 主轴总是中空的 , 举个例子而言 ,它在整个 长度方向上是空的 . 如果采取连续生产杆状怌料可以通过这个洞进给 . 当然 , 这个洞有一个锥形表面用于安装车床顶尖 . 这个外部表面由螺纹连接吸盘，尖盘以及类似的 . 尾座 . 尾座基本上三个部份组成，下部分的基础，一个中间的部份和尾部组成 . 下部份的基础是沿着机床床身导轨上滑动的铸件，而且它有一个定位装置使其锁定在整个尾座的任何需要的位置 ,根据工件的长度 . 中间部分是一个能沿着横向移动用的铸件 . 第三个部份套筒 , 是一个硬化处理的钢管 , 它可以根据需要滑进滑出中间部分 . 它可以通过手轮的使用和一个螺丝 钉，在附近固定在套筒上套筒可以被夹具锁定在沿着行动路径的任何点上 . 13 刀架 . 刀架的主要功能是用在刀具的安装和纵向和横向的进给 . 当被机床 V 形导轨引导的时候，它实际上是在主轴箱和尾座之间滑动的一个 H 形块 .刀架可以用手动或机械方式通过托板箱和丝杠或光杠移动。 当用于加工螺纹的时候 , 动力托板箱的齿轮箱提供的 . 在所有的其他车削操作方面 , 它是由光杠提供动力驱动刀架的。丝杠通过一对半螺钉固定 .这个螺钉安装在托板箱的后面，当操作特定的杠杆时两个半螺钉一起被夹紧而且与旋转的丝杠构成一个完整的螺钉 , 当进给时沿床身 和刀架一起 . 当杠杆脱离的时候，这两个半螺钉离开并且刀架停止运动 . 另一方面，当使用光杠的时候，它经过蜗轮提供力量给托板箱 . 后者对于光杠和沿着光杠移动的丝杠是关键的 ,它在整个长度是关键的一部分 . 一个现代的车床通常在主轴箱之下位于一个快速变速的齿轮箱和经过一列齿轮传动的主轴 . 刀架被连接到丝杠和光杠而且能够通过操作杠杆迅速简单地选择一系列的进给 , 变速齿轮箱应用于普通的车削、平面和螺纹的切削操作 . 因为那齿轮箱被连接到主轴上的 , 对于托板箱移动的距离可以被控制。 . 车床切断工具 形状和车床工具的几何 尺寸根据车床应用的目的而决定 . 车削刀具可以分为两种主要的类型即外部的切削刀具和内部的切削刀具 , 每一个这些小组包括刀具的有下列类型 : 车刀 . 车刀能用于精加工或者粗加工的工具 . 粗加工的车刀具有小的鼻子半径用于大的切削用量 . 另一方面精加工的车刀具有大的鼻子半径用于获得最终需要的尺寸这个尺寸通过小的切削深度获得高的表面质量。粗车刀具有用右手或左手的两种类型 ,根据进给的方向而定 . 它们能有直的 , 弯的 , 或偏置的刀柄 . 平面车刀 . 平面车刀用于待加工的表面或者端面的平面加工 . 这些刀具有用左手边操作 加工表面的和用右手边操作加工表面的 . 这些表面通过刀具的横向进给实现 , 和车削刀具相反的是 , 纵向进给通常被应用 . 切断刀具 . 切断刀具 ,有时叫做分离刀具 ,可用于切断工件以及 / 或以机器制造外的凹槽 . 螺纹车到 . 螺纹车具有三角形的 , 正方形 , 或 梯形的刃口 , 取决于需要的螺纹的横截面的样式。同时 , ，这些刀具的面角度总是一定和那些螺纹现状相同的 . 螺纹切削刀具的直刀柄用于外部的螺纹切削而偏置刀具用于外部螺纹的切削 . 成形车刀 . 成形车刀是特别用于加工特殊形式截面的加工刀具 ,与被以机器制造的希望工件的形 状相反 . 高速钢刀具通常是做成单独的一块整体和硬质合金刀具或陶瓷刀具相反的是 , 它们是做成刀尖的形式 . 后者是由焊接的或者机械方式夹紧与刀柄构成一个整体 . 图 .11.2 指出了一系列后者的类型 ,这些包括碳化物顶尖、断屑器、刀片，紧固螺 14 丝钉 (一个垫圈和一个螺钉 ) 和刀柄 . 当做名字所说的那样，断屑器的功能是时不时的切断切屑 ,如此避免长的带状切屑形成这些带状切屑在操作时可能会带来问题 . 碳化物顶尖 ( 或陶瓷的顶尖 ) 可以有不同的形状 , 根据他们应用的机床操作 . 顶尖可以是一个整体或者是中央有 一个洞 ,根据这个顶尖是焊接还是用机械夹紧方式使其安装在刀柄上。 车床操作 在下列的段落中 , 我们将讨论能在传统的车床上被运行的各种不同的机床操作 . 这个必须铭记于心 , 然而，现代的数控车床具有更多的功能 并且能做其他的操作 ,比如成形加工 , 举例来说 . 下列各项是普通的车床操作 . 外圆车削 . 外圆车削是最简单的和最通常的车床操作 . 工件每旋转一周就在工件上产生一个圆心在车身轴线上的轨道 ； 这个动作的多次产生才能实现切削加工 . 加工的结果是一个具有很小螺距的螺旋线 . 结果 , 已加工表面是圆形的 . 轴向进给是由刀架或者是小刀架提供 ,可用手动或自动化方式实现 , 然而削减的深度由横向进给实现 . 在粗车加工时，一般推荐大的切削深度 (从 0.25 到 6 毫米左右 , 取决于工件的材料 ) 并且会采取较小的进给量 . 另一方面 , 非常小的进给量 , 非常小切削深度 (小于 0.05 或 0.4 毫米 ), 和高的切削速度应用于精加工 . 平面车削 . 平面加工的结果是一平表面这个表面既可以是整个端面或或者是轴间处的一个环形表面 . 在平面车削过程中，进给量是由横向进给提供的，然而削减的深度是有刀架或者小刀架提供 的 . 平面车削可以从工件的外圆向中心也可以从工件的中心向外圆 . 很明显这两种加工都产生螺旋形的加工轨迹 . 通常，在平面加工过程中最好要夹紧刀架 , 因为切削力容易推动刀具 ( 当然 , 整个的刀架 ) 远离工件 . 在大多数平面加工过程中，工件被夹紧在吸盘上或者工作台上 凹槽切削 . 在切断和切槽的加工中 ,只应用刀具的横向进给 . 那切断和切槽工具 , 在先前已经讨论过了 , 用过了 . 钻孔和内表面车削 . 钻孔和内表面车削是在工件内表面上有钻杆或者是适当的内表面切削刀具 , 如果最初的工件是实心的，必须先进行钻 孔加工 . 钻孔刀具安装在刀架上 , 而后刀架相对于工件进行进给 . 圆锥面车削 . 圆锥面车削是通过驱动刀具沿着与车床轴线方向不平行而是与轴线倾斜方向即想得到的圆锥角 . 下列各项是用圆锥面车削的不同的方法 : （ 1）旋转小刀架上的刀盘使其达到半顶角的度数 . 进给是通过手动方式旋转小刀架上的手柄方式完成的 . 这一个方法大多数应用于较大的内圆锥角和角大的外圆锥角切削 . （ 2）采用专用成形刀具 , 对非常短的锥形表面加工 . 工件的宽度一定要比刀具的 15 稍微小一点，而且工件通常被安装在吸盘上或者在工作台上 . 在这种 情形下 , 只有横向进给应用于这种加工过程中而且刀架被夹紧到机器床身上 . （ 3）偏置尾座中心 . 这一个方法应用于较长的和锥角较小（小于 8 度）的外圆锥面车削。 工件被装在两个顶尖之间 ； 然后尾座在垂直于车床主轴线移动距离 S. （ 4）采用锥面切削装置 . 这一个方法应用于车削较长的工件。 当长度比小刀架长度还要大时 . 在如此的情况横向进给机构和刀架完全脱离 ,然后横向进给由附加装置提供 . 在这一个过程中 , 自动的轴向进给能像往常一样使用 . 这一个方法是为非常长的工件以及比较小的圆锥体角度 ,比如 8 度到 10 度。 车削螺纹 . 当进行螺纹切削的时候 , 轴向进给必须保持恒定的速度 ,速度大小取决于工件工件转速 (转 /每分 ) . 两者之間的关系主要有切削螺纹的螺距决定 . 正如先前提到的那样 ,通过丝杠切削螺纹自动产生的 ， 轴向进给驱动刀架 。当丝杠旋转一周时刀架运动距离等于丝杠的螺距，因此，如果丝杠旋转速度等于主轴旋转速度（工件主轴）切削结果工件螺距等于丝杠螺距 丝杠螺距 工件转速 = = 主轴和刀架的传动比 工件螺距 丝杠速度 这个等式对于车床主轴和丝杠的传动链的决定很有用具体的说也就是对传动链中齿轮的选择很有帮助 . 在螺纹切削加工过程中 , 相对较长的工件安装在吸盘上或者在车床两顶尖之间 . 使用的刀具的形状必须与要切削螺纹轮廓非常精确 , 比如三角形的车刀必须用于切削三角形螺纹，以此类推。 滚花加工 . 滚花加工主要是一种成形加工方式，这种加工没有切屑的产生 . 这种加工方法是用两 个有粗銼式的表面的硬化滚轴压在滚动工件上在工件表面上产生塑性变形。 滚花加工应用于比较粗糙的外圆柱面 ( 或者圆锥面 ) ,通常用来做手柄 . 有时侯，表面仅仅用来做装饰用 ； 而且有不同式样滚花可供选择 . 切削速度和进给量 切削速度 , 通常由每分钟表面的进给量 (SFM)表示 , 是在一分钟内在工件的表面 (正在削减 )沿切削方向移动的数量 . 表面的切削速度和转 /每分之间的关系根据下列等式有 : SMF=3.14* DN 在这里： D = 工件的直径 16 N = 转 /每分 表面的切削速度主要取决于加工工件的材料，刀具的材料 , 和通过手册获得的关于切削刀具的信息 . 通常 , SFM 指的是 100 当切削冷压钢或低碳钢时 ,当较强硬的金属时取 50 , 当较软材料取 2