机械工程英语第二版

机械 工程 路基工程安全技术交底工程项目施工成本控制工程量增项单年度零星工程技术标正投影法基本原理 英语第二版 第一单元 • Types of Materials 材料 关于××同志的政审材料调查表环保先进个人材料国家普通话测试材料农民专业合作社注销四查四问剖析材料 的类型 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. 材料可以按多种方法分类。科学家常根据状态将材料分为:固体、液体或气体。他们也把材料分为有机材 料(曾经有生命的)和无机材料(从未有生命的)。 For industrial purposes, materials are divided into engineering materials or nonengineering materials. Engineering materials are those used in manufacture and become parts of products. 就工业效用而言，材料被分为工程材料和非工程材料。那些用于加工制造并成为产品组成部分的就是工程 材料。 Nonengineering materials are the chemicals, fuels, lubricants, and other materials used in the manufacturing process, which do not become part of the product. 非工程材料则是化学品、燃料、润滑剂以及其它用于加工制造过程但不成为产品组成部分的材料。 Engineering materials may be further subdivided into: ?Metal ?Ceramics ?Composite ?Polymers, etc. 工程材料还能进一步细分为:?金属材料?陶瓷材料?复合材料 ?聚合材料，等等。 • Metals and Metal Alloys 金属和金属合金 Metals are elements that generally have good electrical and thermal conductivity. Many metals have high strength, high stiffness, and have good ductility. 金属就是通常具有良好导电性和导热性的元素。许多金属具有高强度、高硬度以及良好的延展性。 Some metals, such as iron, cobalt and nickel, are magnetic. At low temperatures, some metals and intermetallic compounds become superconductors. 某些金属能被磁化，例如铁、钴和镍。在极低的温度下，某些金属和金属化合物能转变成超导体。 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. 合金与纯金属的区别是什么,纯金属是在元素周期表中占据特定位置的元素。例如电线中的铜和制造烹饪 箔及饮料罐的铝。 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 chromium; and gold jewelry which usually contains an alloy of gold and nickel. 合金包含不止一种金属元素。合金的性质能通过改变其中存在的元素而改变。金属合金的例子有:不锈钢是一种铁、 镍、铬的合金，以及金饰品通常含有金镍合金。 Why are metals and alloys used? Many metals and alloys have high densities and are used in applications which require a high mass-to-volume ratio. 为什么要使用金属和合金,许多金属和合金具有高密度，因此被用在需要较高质量体积比的场合。 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. 某些金属合金，例如铝基合金，其密度低，可用于航空航天以节约燃料。许多合金还具有高断裂韧性，这意味着它 们能经得起冲击并且是耐用的。 What are some important properties of metals? Density is defined as a material’s mass divided by its volume. Most metals have relatively high densities, especially compared to polymers. 金属有哪些重要特性, 密度定义为材料的质量与其体积之比。大多数金属密度相对较高，尤其是和聚合物相比较而言。 Materials with high densities often contain atoms with high atomic numbers, such as gold or lead. However, 1 some metals such as aluminum or magnesium have low densities, and are used in applications that require other metallic properties but also require low weight. 高密度材料通常由较大原子序数原子构成，例如金和铅。然而，诸如铝和镁之类的一些金属则具有低密度，并被用 于既需要金属特性又要求重量轻的场合。 Fracture toughness can be described as a material’s 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 won’t shatter. 断裂韧性可以描述为材料防止断裂特别是出现缺陷时不断裂的能力。金属一般能在有缺口和凹痕的情况下 不显著削弱，并且能抵抗冲击。橄榄球运动员据此相信他的面罩不会裂成碎片。 Plastic deformation is the ability of bend or deform before breaking. As engineers, we usually design materials so that they don’t deform under normal conditions. You don’t want your car to lean to the east after a strong west wind. 塑性变形就是在断裂前弯曲或变形的能力。作为工程师，设计时通常要使材料在正常条件下不变形。没有 人愿意一阵强烈的西风过后自己的汽车向东倾斜。 However, sometimes we can take advantage of plastic deformation. The crumple zones in a car absorb energy by undergoing plastic deformation before they break. 然而，有时我们也能利用塑性变形。汽车上压皱的区域在它们断裂前通过经历塑性变形来吸收能量。 The atomic bonding of metals also affects their properties. In metals, the outer valence electrons are shared among all atoms, and are free to travel everywhere. Since electrons conduct heat and electricity, metals make good cooking pans and electrical wires. 金属的原子连结对它们的特性也有影响。在金属内部，原子的外层阶电子由所有原子共享并能到处自由移 动。由于电子能导热和导电，所以用金属可以制造好的烹饪锅和电线。 It is impossible to see through metals, since these valence electrons absorb any photons of light which reach the metal. No photons pass through. 因为这些阶电子吸收到达金属的光子，所以透过金属不可能看得见。没有光子能通过金属。 Alloys are compounds consisting of more than one metal. Adding other metals can affect the density, strength, fracture toughness, plastic deformation, electrical conductivity and environmental degradation. 合金是由一种以上金属组成的混合物。加一些其它金属能影响密度、强度、断裂韧性、塑性变形、导电性 以及环境侵蚀。 For example, adding a small amount 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. 例如，往铝里加少量铁可使其更强。同样，在钢里加一些铬能减缓它的生锈过程，但也将使它更脆。 第七单元 1. Rake angle. It is the angle between the face of the tool called the rake face and the normal to the machining direction. Higher the rake angle, better is the cutting and less are the cutting forces, increasing the rake angle reduces the metal backup available at the tool rake face. 1.前角:它是被称为前倾面的刀具面与垂直机加工方向的夹角。前角越大，则切削越好且切削力越小，增加 前角可以减少刀具前倾面上产生的金属阻塞。 This reduces the strength of the tool tip as well as the heat dissipation through the tool. Thus, there is a maximum limit to the rake angle and this is generally of the order of 15?for high speed steel tools cutting mild steel. It is possible to have rake angles at zero or negative. 但这会和减少通过刀具散发的热量一样减少刀尖强度。因此前角有一最大限制，用高速钢刀具切削低碳钢通常为 15?。前角取零度或负值也是可能的。 2. Clearance angle. This is the angle between the machined surface and the underside of the tool called the flank face. The clearance angle is provided such that the tool will not rub the machined surface thus spoiling the surface and increasing the cutting forces. A very large clearance angle reduces the strength of the tool tip, and hence normally an angle of the order of 5~6?is used. 2. 后角:这是机加工面与被称为后侧面的刀具底面夹角。后角使刀具不产生会损坏机加工面的摩擦和增加 2 切削力。很大的后角会削弱刀尖的强度，因此一般采用5~6?的后角。 (1) Discontinuous chip (2) Continuous chip (3) Continuous chip with BUE (Built up edge) (1)间断切屑 (2)连续切屑 (3)带切屑瘤的连续切屑 Discontinuous Chip. The segmented chip separates into short pieces, which may or may not adhere to each other. Severe distortion of the metal occurs adjacent to the face, resulting in a crack that runs ahead of the tool. 间断切屑:分段的切屑分散成小碎片，既可能相互附着也可能不相互附着。在靠近切削面处发生金属的剧烈 变形，导致在运动刀具前方金属层产生裂缝。 Eventually, the shear stress across the chip becomes equal to the shear strength of the material, resulting in fracture and separation. With this type of chip, there is little relative movement of the chip along the tool face, Fig.7.3a. 最后，横过切屑的剪切应力与材料的剪切强度相等，造成断裂和分离。生成这类切屑时，切屑沿刀具面几乎没有相 对运动，见图7.3a。 Continuous chip. The continuous chip is characterized by a general flow of the separated metal along the tool face. There may be some cracking of the chip, but in this case it usually does not extend far enough to cause fracture. 连续切屑:连续的切屑一般具有分离金属沿刀具面流动的特征。切屑可能有一些破裂，但在这种情况下切屑 通常不会延长到足以引起断裂。 This chip is formed at the higher cutting speeds when machining ductile materials. There is little tendency for the material to adhere to the tool. The continuous chip usually shows a good cutting ratio and tends to produce the optimum surface finish, but it may become an operating hazard, Fig.7.3b. 这种切屑形成于用较高切削速度机加工有延展性的材料时。材料几乎没有粘附刀具的倾向。连续切屑通常具有良好 的切削率和趋向于产生最适宜的表面光洁度，但可能成为操作的危险之源，见图7.3b。 Continuous with a built-up edge. This chip shows the existence of a localized, highly deformed zone of material attached or “welded” on the tool face. 带切屑瘤的连续切屑:这种切屑显示了粘合或“焊接”在刀具面上材料局部高度变形区的存在。 Actually, analysis of photomicrographs shows that this built-up edge is held in place by the static friction force until it becomes so large that the external forces acting on it cause it to dislodge, with some of it remaining on the machined surface and the rest passing off on the back side of the chip, Fig.7.3c. 实际上，对显微照片的分析显示这种切屑瘤受到静摩擦力抑制直至它变得大到作用在它上面的外力使其移动，一些 留在机加工表面上而另一些延伸到切屑的背面，见图7.3c。 • Cutting Fluids 切削液 The functions of cutting fluids (which are often erroneously called coolants) are: • To cool the tool and workpiece • To reduce the friction 切削液(经常误称为冷却液)的功能如下: • 冷却刀具和工件 • 减少摩擦 • To protect the work against rusting • To improve the surface finish • To prevent the formation of built-up edge • To wash away the chips from the cutting zone • 保护工件不生锈 • 改善表面光洁度 • 防止切屑瘤的形成 3 • 从切削区冲掉切屑 However, the prime function of a cutting fluid in a metal cutting operation is to control the total heat. This can be done by dissipating the heat generated as well as reducing it. The mechanisms by which a cutting fluid performs these functions are: cooling action and lubricating action. 然而，在金属切削作业中切削液的主要功能是控制总热量。这可通过既散发又减少所产生的热量来达到。 切削液实现这些功能的机理是:冷却作用和润滑作用。 Cooling action. Originally it was assumed that cutting fluid improves the cutting performance by its cooling properties alone. That is why the name coolant was given to it. 冷却作用:最初设想切削液仅仅是通过冷却特性来改善切削作业。这也是它曾被称为冷却液的原因。 Since most of the tool wear mechanisms are thermally activated, cooling the chip tool interface helps in retaining the original properties of the tool and hence prolongs its life. 由于大多数刀具的磨损机理都是由热引起的，冷却切屑刀具接触界面有助于保持刀具的原有特性，从而延长其使用 寿命。 However, a reduction in the temperature of the workpiece may under certain conditions increase the shear flow stress of the workpiece, thereby decreasing tool life. It has been shown through a number of investigations that cooling in fact is one of the major factors in improving the cutting performance. 可是工件温度的降低在特定条件下会增加工件的剪切流动应力，从而降低刀具寿命。通过一些研究已经表明实际上 冷却只是改善切削作业的主要因素之一。 Lubricating action. The best improvement in cutting performance can be achieved by the lubricating action since this reduces the heat generated, thus reducing the energy input to the metal cutting operation. 润滑作用:切削作业的最大改善可通过润滑作用来达到，由于它减少了热量的产生因而减少了金属切削作 业的能量输入。 However, if the cutting fluid is to be effective, it must reach the chip tool interface. But it is not easy to visualize how it is accomplished in the case of a continuous turning with a single point turning tool, specially when the chip-tool contact pressure is as high as 70 MPa. 可是，如果要使切削液起作用就必须让它到达切屑刀具接触界面。但如何在采用单尖刀具连续车削的场合尤其是切 屑-刀具接触压力高达70MPa时实现并非易事。 Merchant thought that minute asperities existed at the chip-tool interface and the fluid was drawn into the interface by the capillary action of the interlocking network of these surface asperities. Merchant认为:在切屑与刀具接触界面上存在微小的粗粒，切削液通过这些表面的微小粗粒组成连锁的网络的毛细 管被吸入到切屑与刀具的接触界面上。 第十一单元 • The Lathe and Its Construction 车床及其结构 A lathe is a machine tool used primarily for producing surfaces of revolution and flat edges. 车床是主要用于生成旋转表面和平整边缘的机床。 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: 根据它们的使用目的、结构、能同时被安装刀具的数量和自动化的程度，车床—或更确切地说是车床类的机床，可 以被分成以下几类: (1)Engine lathes (2)Toolroom lathes (3)Turret lathes (4)Vertical turning and boring mills (5)Automatic lathes (6)Special-purpose lathes (1)普通车床 (2)万能车床 (3)转塔车床 4 (4)立式车床 (5)自动车床 (6)特殊车床 In spite of that diversity of lathe-type machine tools, they 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. 虽然车床类的机床多种多样，但它们在结构和操作原理上具有共同特性。这些特性可以通过普通车床这一 最常用的代表性类型来最好地说明。下面是关于图11.1所示普通车床的主要部分的描述。 Lathe bed. The lathe bed is the main frame, involving a horizontal beam on two vertical supports. It is usually made of grey or nodular cast iron to damp vibrations and is made by casting. 车床床身:车床床身是包含了在两个垂直支柱上水平横梁的主骨架。为减振它一般由灰铸铁或球墨铸铁铸 造而成。 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 job easily and comfortably. 它上面有能让大拖板轻易纵向滑动的导轨。车床床身的高度应适当以让技师容易而舒适地工作。 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 slide surface of the bed). The spindle is driven through the gearbox, which is housed within the headstock. 主轴箱:主轴箱固定在车床床身的左侧，它包括轴线平行于导轨的主轴。主轴通过装在主轴箱内的齿轮箱 驱动。 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. 齿轮箱的功能是给主轴提供若干不同的速度(通常是6到18速)。有些现代车床具有采用摩擦、电力或液压驱动的 无级调速主轴箱。 The spindle is always hollow, i. e., it has a through hole extending lengthwise. Bar stocks can be fed through that hole if continuous production is adopted. 主轴往往是中空的，即纵向有一通孔。如果采取连续生产，棒料能通过此孔进给。 Also, that hole has a tapered surface to allow mounting a plain lathe center. The outer surface of the spindle is threaded to allow mounting of a chuck, a face plate, or the like. 同时，此孔为锥形表面可以安装普通车床顶尖。主轴外表面是螺纹可以安装卡盘、花盘或类似的装置。 Tailstock. 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 guideways, and it has a clamping device to enable locking the entire tailstock at any desired location, depending upon the length of the workpiece. 尾架:尾架总成基本包括三部分，底座、尾架体和套筒轴。底座是能在车床床身上沿导轨滑动的铸件，它 有一定位装置能让整个尾架根据工件长度锁定在任何需要位置。 The intermediate part is a casting that can be moved transversely to enable alignment of the axis of 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. 尾架体为一能横向运动的铸件，它可以调整尾架轴线与主轴箱轴线成一直线。第三部分，套筒轴是一淬硬钢管，它 能根据需要在尾架体中纵向进出移动。 This is achieved through the use of a handwheel and a screw, around which a nut fixed to the quill is engaged. The hole in the open side of the quill is tapered to enable mounting of lathe centers or other tools like twist drills or boring bars. The quill can be locked at any point along its travel path by means of a clamping device. 这通过使用手轮和螺杆来达到，与螺杆啮合的是一固接在套筒轴上的螺母。套筒轴开口端的孔是锥形的，能安装车 床顶尖或诸如麻花钻和镗杆之类的工具。套筒轴通过定位装置能沿着它的移动路径被锁定在任何点。 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 5 the headstock and tailstock while being guided by the V-shaped guideways of the bed. 大拖板:大拖板的主要功能是安装刀具和产生纵向和/或横向进给。它实际上是一由车床床身V形导轨引导 的、能在车床床身主轴箱和尾架之间滑动的H形滑块。 The carriage can be moved either manually or mechanically by means of the apron and either the feed rod or the lead screw. 大拖板能手动或者通过溜板箱和光杆(进给杆)或丝杆(引导螺杆)机动。 Lathe Cutting Tools 车床切削刀具 The shape and geometry of the lathe tools depend upon the purpose for which they are employed. 车床刀具的形状和几何参数取决于它们的使用目的。 Turning tools can be classified into two main groups, namely, external cutting tools and internal cutting tools. Each of these two groups include the following types of tools: 车削刀具可以分为两个主要组别，即外部切削刀具和内部切削刀具。这两组中的每一组都包括以下类型刀具: Turning tools. Turning tools can be either finishing or rough turning tools. Rough turning tools have small nose radii and are employed when deep cuts are made. 车削刀具:车削刀具可以是精车刀具或粗车刀具。粗车刀具刀尖半径较小，用于深切削。 On the other hand, finishing tools have larger nose radii and are used for obtaining the final required dimensions with good surface finish by making slight depths 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. 而精车刀具刀尖半径较大，用于通过微量进刀深度来获得具有较好表面光洁度的最终所需尺寸。粗车刀具按其进给 方向可以是右手型的或是左手型的。它们可以有直的、弯的或偏置的刀杆。 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. 端面刀具:端面刀具用在端面作业中加工平板侧面或端部表面，也有加工左右侧表面之分。与一般采用纵 向进给的车削作业相反，那些侧表面通过采用横向进给产生。 Cutoff tools. Cutoff tools, which are sometimes called parting tools, serve to separate the workpiece into parts and/or machine external annular grooves. 切断刀具:切断刀具，有时也称为分割刀具，用于将工件分割成若干部分和/或加工外部环形槽。 Thread-cutting tools. Thread-cutting tools have either triangular, square, or trapezoidal 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. 螺纹切削刀具:螺纹切削刀具根据所需螺纹的横截面，有三角形的、矩形的或梯形的切削刃。同时，这些 刀具的平面角必须始终与螺纹形状的平面角保持一致。 Thread-cutting tools have straight shanks for external thread cutting and are of the bent-shank type when cutting internal threads. 车外螺纹的螺纹切削刀具为直刀杆，而车内螺纹的螺纹切削刀具则是弯刀杆。 Form tools. Form tools have edges especially manufactured to take a certain form, which is opposite to the desired shape of the machined workpiece. 成形刀具:成形刀具有专门制成特定形状的刀刃，这种刀刃形状与被加工工件所需外形正好相反。 An HSS tool is usually made in the form of a single piece, contrary to cemented carbides or ceramic, which are made in the form of tips. The latter are brazed or mechanically fastened to steel shanks( 高速钢刀具通常以单件形式制造，而硬质合金或陶瓷刀具则以刀尖形式制造。后者用铜焊或机械方法固定于钢质刀 杆上。 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. 图11.2所示为机械式固定布置方式，它包括了硬质合金刀尖、断屑槽、衬垫、卡装螺杆(带有垫圈和螺母)及刀杆。 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 operation. 6 顾名思义，断屑槽的功能就是不时地折断长切屑，以防形成很长的可能会在机加工操作中引起问题的缠绕切屑条。 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. 硬质合金刀尖(或陶瓷刀尖)根据采用它们的机加工操作，可以有不同的形状。根据将刀尖装配在刀杆上是通过用铜 焊还是机械卡装，刀尖可以是实心的或是带有中心通孔的。 Taper turning. Taper turning is achieved by driving the tool in a direction that is not parallel 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: 锥面车削:锥面车削通过沿着与车床主轴不平行而倾斜成一个等于锥面所需角度的方向进刀来实现。下面 是在实际锥面车削中采用的不同方法: (1) Rotating the disc of the compound rest with an angle equal 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. (1) 将复式刀架盘旋转一个等于圆锥体顶角一半的角度。通过摇动复式刀架操纵柄手动提供进给。当锥角相对较大 时切削外锥面和内锥面推荐使用这种方法。 (2) Employing special form tools for external, very short, conical surfaces. The width of 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. In this case, only the cross feed is used during the machining process and the carriage is clamped to the machine bed. (2) 对很短的外锥面采用特殊的成型刀具。工件的宽度必须略小于刀具的宽度，并且工件通常由卡盘支撑或夹紧在 花盘上。在这种情况下，机加工作业时只有横向进给而大拖板则夹紧在床身上。 (3) Offsetting the tailstock center. This method is employed for external taper turning of long workpieces that are required to have small taper 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. (3)偏移尾架顶尖。对需要较小锥角(小于8?) 的较长工件外锥面车削采用这种方法。工件安装于两顶尖之间;然 后将尾架顶尖朝垂直于车床主轴方向移动一距离S。 (4) Using the taper-turning attachment. This method is used for turning very long workpieces, 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. (4) 采用锥面车削附加装置。这种方法用于车削很长的工件，其长度大于复式刀架的整个行程。在这种场合下要遵 循的步骤是将横向滑板完全脱离大拖板，然后通过锥面车削附加装置进行引导。 During this process, the automatic axial feed can be used as usual. This method is recommended for very long workpieces with a small cone angle, i.e., 8?through 10?. 在此作业中，能照常使用自动轴向进给。对具有较小锥角(即8?到10?)的很长工件推荐采用这种方法。 Cutting Speeds and Feed 切削速度和进给 第十二单元 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 consists of a neck and a shank that can be either straight or tapered. 麻花钻:麻花钻是最常用的钻头类型。它有两条切削刃和两条沿钻头体全长连续的螺旋状出屑槽，如图12.1 所示。麻花钻还包括钻颈和钻柄，钻柄可以是直的也可以是锥形的。 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. 锥形钻柄通过楔入动作安装在主轴的锥形轴孔中，钻柄上还有柄舌插入主轴轴孔中的插槽，从而作为传递转动的可 靠方法。 On the other hand, straight-shank drills are held in a drill chuck that is, in turn, fitted into the 7 spindle socket in the same way as tapered shank drills. 另一方面，直柄钻头用钻头卡盘夹住，接下来钻头卡盘则象锥形钻柄钻头一样安装在主轴轴孔内。 Core drills. A core drill consists of the chamfer, body, neck, and shank, as shown in Fig.12.2. This type of drill may have either three or four flutes and equal number of margins, which ensure superior guidance, thus resulting in high machining accuracy. 空心钻:空心钻包括斜面、钻头体、钻颈和钻柄，如图12.2所示。这类钻头可以有三条或四条出屑槽及相 同数量的保证良好导向的导向边，这样使得加工有高精度。 It can also be seen in Fig.12.2 that a core drill has flat end. The chamfer can have three or four cutting edges or lips, and the lip angle may vary between 90?and 120?. 在图12.2中同样能看到，空心钻具有平坦的端部。斜面可以有三或四条切削刃或钻唇，并且钻唇角可以在90?到 120?之间变化。 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. 空心钻用于扩大已有的孔而不是打孔。这类钻头具有较大生产率、高加工精度和优良钻削表面质量的特性。 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. 深孔钻:深孔钻用于钻深孔。所有深孔钻都是直出屑槽的，并且均为单切削刃。钻头体中有个孔作为导管 在相当大的压力下将冷却液传送到钻头顶端。 Milling and Milling Cutter 铣削和铣刀 Up milling (conventional milling). In up milling the workpiece is fed against the direction of cutter rotation, as shown in Fig.12.3a. As we can see in that figure, the depth of cut (and consequently the load) gradually increases on the successively engaged cutting edges. 逆铣(传统铣削):在逆铣中，工件逆着铣刀转动的方向进给，如图12.3a所示。就像在此图中能看到的那 样，切削深度(及作为结果的载荷)随着切削刃持续进入切削而逐渐增加。 Therefore, the machining process involves no impact loading, thus ensuring smoother operation 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. 所以，这种工艺没有冲击载荷，从而保证了机床的较平稳运行和较长寿命。通过逆铣所得机加工表面质量不是很高。 然而逆铣仍经常被用在工业上，尤其是粗切削时。 Down milling (climb milling). As can be seen in Fig.12.3b, 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 depth of cut is achieved directly as the cutter engages with the workpiece. 顺铣(同向铣削):如同在图12.3b中看到的那样，在顺铣时刀具与工件之间接触点上铣刀旋转与进给方向 一致。还可以看到当刀具进入工件切削时直接达到最大切削深度。 This results in a kind of impact, or sudden loading. Therefore, this method cannot be used unless the milling machine is equipped with a backlash eliminator on the feed screw. The advantages of this method include higher quality of the machined surface and easier clamping of workpieces, since the cutting forces act downward. 这会导致一种冲击，或突然加载。因此，这种方法只有当铣床在进给螺栓上配备间隙消除器时才采用。这种方法的 优点包括机加工表面质量较高和工件由于切削力向下作用而较容易夹紧。 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.12.4a. This type is always mounted on horizontal milling machines and is used for machining flat surfaces. 平面铣刀:平面铣刀是一种盘状切削刀具，它可以具有直齿或螺旋齿，如图12.4a所示。这类铣刀总是安装 在卧式铣床上，用于机加工平面。 Face milling cutter. A face milling cutter is also used for machining flat surfaces. It is bolted at the end of a short arbor, which is in turn mounted on a vertical milling machine. Fig.12.4b indicates 8 a milling cutter of this type. 端面铣刀:端面铣刀也可用于机加工平面。它用螺栓固定在短刀杆的端部，而短刀杆则依次安装于立式铣床 上。图12.4b显示了这类铣刀。 Plain metal slitting saw cutter. Fig.12.4c indicates a plain metal slitting saw cutter. we can see that it actually involves a very thin plain milling cutter. 平面金属开槽锯刃铣刀:图12.4c显示了一种平面金属开槽锯刃铣刀。可以看到它其实是一种很薄的平面铣 刀。 Side milling cutter. A side milling cutter is used for cutting slots, grooves, and splines. As shown in Fig.12.4d, it is quite similar to the plain milling cutter, the difference being that this type has teeth on the sides. As is the case with the plain cutter, the cutting teeth can be straight or helical. 侧铣刀:侧铣刀用于切削狭槽、凹槽和花键槽。正如图12.4d所示，它与平面铣刀十分相似，差别在于此 类铣刀齿在侧面。象平面铣刀的情况一样，切削齿既可以是直的也可以是螺旋的。 Angle milling cutter. An angle milling cutter is employed in cutting dovetail grooves, ratchet wheels, and the like. Fig.12.4e indicates a milling cutter of this type. 倾斜铣刀:倾斜铣刀用于切削燕尾槽、棘轮之类的。图12.4e显示了这类铣刀。 T-slot cutter. As shown in Fig.12.4f, 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. T型槽铣刀:如图12.4f所示，T型槽铣刀包括了一个平面铣刀和一根垂直于它的整体轴。正像其名字所表 明的，这类铣刀用于铣削T型槽。 End mill cutter. End mill cutters find common applications in cutting slots, grooves, flutes, splines, pocketing work, and the like. Fig.12.4g indicates an end mill cutter. The latter is always mounted on a vertical milling machine and can have two or four flutes, which may be either straight or helical. 端面铣刀:端面铣刀在切削狭槽、凹槽、长凹槽、花键槽、凹状工件之类时均能发现其普遍应用。图12.4g 为端面铣刀。它总是安装在立式铣床上，并具有两到四条既可是直的也可是螺旋的长凹槽。 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. From milling cutters are mounted on horizontal milling machines. 成形铣刀:成形铣刀的齿具有特定的形状，这个形状与铣削时要切削的那部分金属的形状一致。这类铣刀 的例子包括齿轮铣刀、齿轮滚刀、凸形和凹形铣刀等等。成形铣刀安装在卧式铣床上。 第十三单元 1) The location of workpiece. Fig.13.1 represents a body that is completely free in space. In this condition it has six degrees of freedom. Consider these freedoms with respect to the three mutually perpendicular axes XX, YY, and ZZ. 1) 工件的定位:图13.1表示一个在空间完全自由的物体，在这种情况下它具有六个自由度。相对于三根互 相垂直的坐标轴XX、YY和ZZ来考虑这些自由度。 The body can move along any of these axes; it therefore has three freedoms of translation. It can also rotate about any of the three axes; it therefore has three freedoms of rotation. The total number of freedoms is six. When work is located, as many of these freedoms as possible must be eliminated, to ensure that the operation is performed with the required accuracy. 此物体能沿三根坐标轴的任意一根移动;这样就具有三个平移自由度。它也能围绕三根坐标轴的任意一根回转;这 样它又具有三个旋转自由度。总的自由度数目是六个。当工件被定位时，必须尽可能多地消除这些自由度，以保证 作业按要求精度进行。 Accuracy is ensured by machining suitable location features as early as possible, and using them for all location, unless other considerations mean that other location features must be used. If it is necessary, the new location features must be machined as a result of location from the former location features. 除非有必要采用另外定位要素的其它考虑，精度可通过尽可能早地加工合适的定位要素并采用它们进行所有定位来 保证。如果必要的话，新的定位要素必须作为先前的定位要素的定位结果来加工。 2) The clamping of the workpiece. The clamping system must be such that the workpiece is held against 9 the cutting forces, and the clamping forces must not be so great as to cause the workpiece to become distorted or damaged. 2) 工件的装夹:装夹系统必须使工件对着切削力夹持，而且装夹力又不能大得引起工件变形或损坏。 The workpiece must be supported beneath the point of clamping, to ensure that the forces are taken by the main frame of the jig or fixture, and on to the machine table and bed. When jigs and fixtures are designed, the clamping system is designed to ensure that the correct clamping force is applied, and that the clamps can be operated quickly but with safety. 工件必须在装夹点下被支撑，以保证这些力由钻模或夹具的主框架来承受并传递给机器台和床身。在设计钻模和夹 具时，要同时设计装夹系统来保证提供恰当的装夹力，并使装夹操作快速而安全。 10