第九章 Lapping 研磨
Lapping is a finishing operation used on flat and cylindrical surfaces.The lap, shown in Fig.9.1a, is usually made of cast iron, copper, leather, or cloth.
研磨是一种用于平面和圆柱面的精加工作业。研具，如图9.1a所示，通常用铸铁、铜、皮革或布制成。
The abrasive particles are embedded in the lap, or they may be carried through slurry.Depending on the hardne of the workpiece, lapping preures range from 7kPa to 140kPa (1 to 20 psi).研磨微粒嵌入研具内，或者可以通过液体携带。根据工件硬度，研磨压力可在7kPa到140kPa(1到20psi)范围中取。
Lapping has two main functions.Firstly, it produces a superior surface finish with all machining marks being removed from the surface.Secondly, it is used as a method of obtaining very close fits between mating parts such as pistons and cylinders.
研磨有两个主要作用。首先，它通过去除所有机加工痕迹能产生较好的表面光洁度。其次，它能用作获得像活塞与气缸之类配件间过盈配合的方法。
The lapped workpiece surface may look smooth but it is actually filled with microscopic peaks, valleys, scratches and pits.Few surfaces are perfectly flat.Lapping minimizes the surface irregularities, thereby increasing the available contact area.
研磨后的工件表面可能看似平滑，其实布满着微观峰、谷、划痕和凹陷。几乎没有表面是完全平整的。研磨使表面不规则最小化，因而增加了有效接触面积。
The drawing in Fig.9.1a shows two surfaces.The upper one is how a surface might look before lapping and the lower one after lapping.Lapping removes the microscopic mountain tops and produces relatively flat plateaus.Entire microscopic mountain ranges may need to be ground down in order to increase the available contact area.图9.1a上显示了两个表面。上面是研磨前表面可能的外观模样而下面则是研磨后的模样。研磨去除了微观峰顶从而产生相对平坦的平台。整个微观山脉范围都需要磨去以增加有效接触面积。
Production lapping on flat or cylindrical pieces is done on machines such as those shown in Fig.9.1b and 9.1c.Lapping is also done on curved surfaces, such as spherical objects and lenses, using specially shaped laps.
研磨平面或圆柱面工件的生产过程是在如图9.1b和9.1c那样的机器上完成的。研磨也可采用特殊成型研具在诸如球形物体和透镜之类的曲面上进行。 Polishing
抛光
Polishing is a proce that produces a smooth, lustrous surface finish.Two basic mechanisms are involved in the polishing proce: (a) fine-scale abrasive removal, and (b) softening and smearing of surface layers by frictional heating during polishing.
抛光是生成平滑、有光泽表面光洁度的工艺。抛光工艺涉及两种基本机理： (a)精细等级磨粒去除，和(b)在抛光中通过摩擦生热软化并抹光表面层。 Electropolishing
Electropolishing is an electrochemical proce similar to, but the reverse of, electroplating.The electropolishing proce smoothes and streamlines the microscopic surface of a metal object.Mirror-like finishes can be obtained on metal surfaces by electropolishing.电解抛光
电解抛光是一种与电镀相似的电化学工艺，但过程与电镀正好相反。电解抛光工艺使金属物体的微观表面平滑和简单化。通过电解抛光能在金属表面得到镜面光洁度。
In electropolishing, the metal is removed ion by ion from the surface of the metal object being polished.Electrochemistry and the fundamental principles of electrolysis (Faraday’s Law) replace traditional mechanical finishing techniques.
在电解抛光中，金属是逐个离子地从被抛光金属物体表面去除的。电化学和电解基本原理(Faraday定理)取代了传统的机械精加工技术。
In basic terms, the object to be electropolished is immersed in an electrolyte and subjected to a direct electrical current.The object is maintained anodic, with the cathodic connection being made to a nearby metal conductor.用基本术语说，要电解抛光的物体被浸没在电解液中并且通上直流电。该物体为阳极，阴极连接到附近的金属导体上。
Smoothne of the metal surface is one of the primary and most advantageous effects of electropolishing.During the proce, a film of varying thickne covers the surface of the metal.This film is thickest over micro depreions and thinnest over micro projections.
金属表面的平滑是电解抛光主要的和最有优势的效应之一。在此过程中，一变化着厚度的膜覆盖在金属表面上。该膜在微观凹陷处最厚而在微观凸出处最薄。
Electrical resistance is at a minimum wherever the film is thinnest, resulting in the greatest rate of metallic diolution.Electropolishing selectively removes microscopic high points or “peaks” faster than the rate of attack on the corresponding micro-depreions or “valleys”.
电阻在膜最薄处最小，导致最大金属分解率。电解抛光选择性地去除微观高点或“峰” 快于对相应微观凹陷处或“谷”的侵蚀速率。
Stock is removed as metallic salt.Metal removal under certain circumstances is controllable and can be held to 0.0001 to 0.0025 mm.原材料以金属盐的形式被去除。在特定环境下金属的去除是可控的并且保持在0.0001 到0.0025mm范围内。
Chemical Mechanical Polishing
Chemical mechanical polishing is becoming an increasingly important step in the fabrication of multi-level integrated circuits.Chemical mechanical polishing refers to polishing by abundant slurry that interacts both chemically and mechanically with the surface being polished.化学机械抛光
化学机械抛光正在多层集成电路制造领域成为日益重要的步骤。化学机械抛光是指大量抛光液与被抛光表面产生化学和机械作用的抛光。
During the chemical mechanical polishing proce, a rotating wafer is preed face down onto a rotating, resilient polishing pad while polishing slurry containing abrasive particles and chemical reagents flows in between the wafer and the pad.在化学机械抛光过程中，旋转晶片面向下压在旋转、有回弹力的抛光衬垫上，而同时含有研磨微粒和化学反应物的抛光液流过晶片与衬垫之间。
The combined action of polishing pad, abrasive particles and chemical reagents results in material removal and polishing of the wafer surface.Chemical mechanical polishing creates flat, damage-free on a variety of brittle materials and it is used extensively on silicon wafers in the manufacture of integrated circuits.抛光衬垫、研磨微粒和化学反应物的共同作用导致晶片表面的材料去除并抛光。化学机械抛光可使多种易碎材料平整且不受损害，因此在集成电路制造中被广泛地用在硅晶片上。
Chemical mechanical polishing is a complicated multiphase proce.It mainly includes the following two dynamics.First, the active component in polishing slurry reacts with the atoms of the wafer, and the proce is chemical reaction step with oxidation-reductive reaction.
化学机械抛光是一种复杂的多相工艺。它主要包括下列两个动态过程：第一，抛光液中活性成分与晶片的原子发生反应，这是带有氧化-还原反应的化学反应步骤。
The second step is the proce of desorption, that is to say, the resultants gradually separate from the wafer surface and new surface is exposed to polishing slurry.If chemical reactive rate is smaller, the total removal rate of the wafer is also small; furthermore, the surface degree of finish is not good.第二步是解吸附过程，即反应产物逐渐从晶片表面分离并将新表面暴露给抛光液。如果化学反应速率较小，晶片的总去除率也较小，而且表面光洁程度不够好。
On the contrary, even if chemical reaction is very rapid, but desorption is very slow, the total removal rate is not good.Because resultants connot separate from the wafer surface, the active component in the polishing slurry cannot expose and react with the atoms on the new surface, which holds up chemical reaction.
与之相反，即使化学反应很快，但解吸附很慢，则总去除率也不够好。因为反应产物不能从晶片表面分离，抛光液中活性成分就不能暴露并与新表面上的原子起反应，这会抑制化学反应。
The balance and compositive effects of two steps decide the total removal rate and its surface degree of finish.这两个步骤的平衡与合成效应决定了总去除率和表面光洁程度。
第十章 Surface Engineering 表面处理
The procees of surface engineering, or surface treatments, tailor the surfaces of engineering materials to: (1) control friction and wear, (2) improve corrosion resistance, (3) change physical property, e.g., conductivity, resistivity, and reflection, (4) alter dimension, (5) vary appearance, e.g., color and roughne, (6) reduce cost.
进行表面工程或表面处理的目的是：(1)控制摩擦和磨损，(2)改善抗腐蚀性，(3)改变物理性能，例如，传导率、电阻系数和反射率，(4)修改尺寸，(5)变更外观，例如颜色和粗糙程度，(6)降低成本。
Common surface treatments can be divided into two major categories: treatments that cover the surfaces and treatments that alter the surfaces.通常的表面处理可以分为两个主要类型：覆盖表面的处理和改变表面的处理。 Covering the Surface覆盖表面
The treatments that cover the surfaces include organic coatings and inorganic coatings.
覆盖表面的处理包括有机涂层和无机涂层。
The inorganic coatings perform electroplatings, conversion coatings, thermal sprayings, hot dippings, furnace fusings, or coat thin films, gla, ceramics on the surfaces of the materials.无机涂层有电镀、转化层、热喷涂、热浸渍、熔炉熔融、或在材料表面涂上薄膜、玻璃、陶瓷。
Electroplating is an electrochemical proce by which metal is deposited on a substrate by paing a current through the bath.
电镀是一种在电镀槽通上电流使金属沉淀在基体上的电化学过程。
Usually there is an anode (positively charged electrode), which is the source of the material to be deposited; the electrochemistry which is the medium through which metal ions are exchanged and transferred to the substrate to be coated; and a cathode (negatively charged electrode) which is the substrate to be coated.
通常有一个阳极(正电极)，是要沉淀材料的来源；电化学反应是使金属离子交换并迁移到要覆盖基体上的中间过程；以及一个阴极(负电极)，即要覆盖的基体。
Plating is done in a plating bath which is usually a non-metallic tank (usually plastic).The tank is filled with electrolyte which has the metal, to be plated, in ionic form.
电镀在通常为非金属容器(一般是塑料)的电镀槽中进行。该容器装满了含有离子态被镀金属的电解液。
The anode is connected to the positive terminal of the power supply.The anode is usually the metal to be plated (auming that the metal will corrode in the electrolyte).For ease of operation, the metal is in the form of nuggets and placed in an inert metal basket made out non-corroding metal (such as titanium or stainle steel).
阳极与电源正极相连。阳极通常为被镀金属(假定该金属能在电解液中腐蚀)。为了操作容易，该金属呈固体小块形式并置于由抗腐蚀金属(如钛或不锈钢)制成的惰性金属筐内。
The cathode is the workpiece, the substrate to be plated.This is connected to the negative terminal of the power supply.The power supply is well regulated to minimize ripples as well to deliver a steady predictable current, under varying loads such as those found in plating tanks.
阴极是工件，即要镀的基体，连接到电源的负极。很好地调节电源使波动最小化并在载荷变化情况(如同电镀容器中看到的那样)下提供稳定的可预知电流。
As the current is applied, positive metal ions from the solution are attracted to the negatively charged cathode and deposit on the cathode.As a replenishment for these deposited ions, the metal from the anode is diolved and goes into the solution and balances the ionic potential.
一旦通上电流，来自溶液的正的金属离子被吸引到带负电的阴极并沉淀在其上。作为这些沉淀离子的补充，来自阳极的金属被溶解并进入溶液平衡离子势能。
Thermal spraying proce.Thermal spraying metal coatings are depositions of metal which has been melted immediately prior to projection onto the substrate.The metals used and the application systems used vary but most applications result in thin coatings applied to surfaces requiring improvement to their corrosion or abrasion resistance properties.
热喷涂工艺：热喷涂金属涂层是金属熔化后立即投射到基体上形成的金属沉积层。所用的金属和应用系统都可以变化，但大多数应用都是在要求改善抗腐蚀或耐磨性能的表面涂上薄层。
Thermal spray is a generic term for a broad cla of related procees in which molten droplets of metals, ceramics, glaes, and/or polymers are sprayed onto a surface to produce a
coating, to form a free-standing near-net-shape, or to create an engineered material with unique properties.
热喷涂是用于很大一类相关工艺的一个通用术语，喷涂到表面产生涂层的熔化小滴可以是金属、陶瓷、玻璃和/或聚合物，形成独立的近似纯形或产生具有独特性能的设计材料。
In principle, any material with a stable molten phase can be thermally sprayed, and a wide range of pure and composite materials are routinely sprayed for both research and industrial applications.Deposition rates are very high in comparison to alternative coating technologies.
大体上，有稳定熔化状态的任何材料都可以热喷涂，范围宽阔的纯净和合成材料一般都能喷涂用于研究及工业目的。其沉积率与可供选择的涂层技术比较是很高的。
Deposit thickne of 0.1 to 1mm is common, and thickne greater than 1cm can be achieved with some materials.沉淀厚度普遍为0.1到1mm，对某些材料则沉淀厚度可以达到1cm以上。
The proce for application of thermal spray metal is relatively simple and consists of the following stages.(1) Melting the metal at the gun.(2) Spraying the liquid metal onto the prepared substrate by means of compreed air.
热喷涂金属的应用工艺相对简单并由下列阶段组成： (1)在喷枪内熔化金属。
(2)通过压缩空气将液态金属喷涂在准备好的基体上。 (3) Molten particles are projected onto the cleaned substrate.
There are two main types of wire application available today namely arc spray and gas spray.(3)熔化微粒投射在清洁过的基体上。
现在有两种主要的金属丝应用类型可选用，也就是电弧喷涂和气体喷涂。
ARC—A pair of wires are electrically energized so that an arc is struck acro the tips when brought together through a pistol.Compreed air is blown acro the arc to atomise and propel the autofed metal wire particles onto the prepared workpiece.
电弧喷涂—当一对金属丝通过手持喷枪连到一起时，通上电横过其末端划燃电弧。压缩空气吹过电弧使其雾化并驱使自动送料金属丝微粒到准备好的工件上。
GAS—In combustion flame spraying the continuously moving wire is paed through a pistol, melted by a conical jet of burning gas.The molten wire tip enters the cone, atomises and is propelled onto the substrate.
气体喷涂—连续移动的金属丝在燃烧火焰喷射中通过手持喷枪，并被燃烧气体的锥形喷嘴所熔化。熔化后的金属丝顶端进入锥体雾化并驱使其到基体上。
Thin-Film Coatings.Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD) are two most common types of thin-film coating methods.
薄膜涂层：物理蒸发沉淀(PVD)和化学蒸发沉淀(CVD)是两种最常见薄膜涂层方法的类型。
PVD coatings involve atom-by-atom, molecule-by-molecule, or ion deposition of various materials on solid substrates in vacuum systems.
物理蒸发沉淀涂层涉及到在真空装置内各种各样的材料原子紧靠原子、分子紧靠分子或离子沉淀于固态基体上。
Thermal evaporation uses the atomic cloud formed by the evaporation of the coating metal
in a vacuum environment to coat all the surfaces in the line of sight between the substrate and the target.It is often used in producing thin, 0.5μm, decorative shiny coatings on plastic parts.
热蒸发利用涂层金属在真空环境中蒸发形成的微粒子雾将基体和靶材之间可见范围内所有表面覆盖。在塑料零件上生成较薄(0.5μm)的、装饰性的、有光泽的涂层时常常用到它。
The thin coating, however, is fragile and not good for wear applications.The thermal evaporation proce can also coat a very thick, 1mm, layer of heat-resistant materials, such as MCrAIY—a metal, chromium, aluminum, and yttrium alloys, on jet engine parts.
然而，这种薄涂层是易碎的并不适合用于磨损场合。热蒸发工艺也能在喷气发动机零件上覆盖很厚(1mm)的耐热材料涂层，例如MCrAIY—一种金属、铬、铝和钇合金。
Sputtering applies high-technology coatings such as ceramics, metal alloys, organic and inorganic compounds by connecting the workpiece and the substance to a high-voltage DC power supply in an argon vacuum system.
反应溅射法通过在氩真空设备中连接工件和具有特定成分的材料到高压直流电来应用诸如陶瓷、金属合金、有机和无机化合物之类的高技术涂层。
The plasma is established between the substrate (workpiece) and the target (donor) and transposes the sputtered off target atoms to the surface of the substrate.等离子区形成于基体(工件)和靶材(原料物质)之间并将被溅射的靶材原子转移到基体的表面上。
When the substrate is non-conductive, e.g., polymer, a radio-frequency (RF) sputtering is used instead.Sputtering can produce thin, le than 3μm (120μin), hard thin-film coatings, e.g., titanium nitride (TIN) which is harder than the hardest metal.
如果基体不导电，例如聚合物，则采用射频(RF)溅射代替。反应溅射法可以生成较薄(小于3μm(120μin))的、坚硬薄膜涂层，像比最硬金属还硬的氮化钛(TIN)。
Sputtering is now widely applied on cutting tools, forming tools, injection molding tools, and common tools such as punches and dies, to increase wear resistance and service life.现在反应溅射法已被广泛应用于切削刀具、成型工具、注射模具和诸如冲头和冲模之类的通用器具，以增强其耐磨性和使用寿命。
CVD is capable of producing thick, dense, ductile, and good adhesive coatings on metals and non-metals such as gla and plastic.Contrasting to the PVD coating in the “line of sight”, the CVD can coat all surfaces of the substrate.
化学蒸发沉淀能在金属和像玻璃和塑料之类的非金属上生成较厚的、致密的、有延伸性的和带良好粘性的涂层。与物理蒸发沉淀在“可见范围”对比，化学蒸发沉淀能将基体的所有表面都覆盖。
Conventional CVD coating proce requires a metal compound that will volatilize at a fairly low temperature and decompose to a metal when it contacts with the substrate at higher temperature.
常规的化学蒸发沉淀涂层工艺需要一种容易在相当低温度下挥发并且在较高温度下与基体接触时能分解成纯金属的金属化合物。
The most well known example of CVD is the nickel carbonyl (NiCO4) coating as thick as 2.5mm (0.1in.) on gla windows and containers to make them explosion or shatter resistant.最为人熟知的化学蒸发沉淀例子是在玻璃窗和容器上镀厚为2.5mm(0.1in.)的羰基镍(NiCO4)涂层使它们能抵抗爆裂或破碎。
Diamond CVD coating proce is introduced to increase the surface hardne of cutting
tools.However, the proce is done at the temperatures higher than 700℃ (1300℉) which will soften most tool steel.
为增加切削刀具表面硬度引入了钻石化学蒸发沉淀涂层工艺。可是此工艺要在高于700℃(1300℉)的温度下才能实现，这温度会软化大多数工具钢。
Thus, the application of diamond CVD is limited to materials which will not soften at this temperature such as cemented carbides.因而钻石化学蒸发沉淀的应用受到材料限制，要求材料在此温度下不软化例如硬质合金。
Plasma-Aisted CVD coating proce can be performed at lower temperature than diamond CVD coatings.This CVD proce is used to apply diamond coatings or silicon carbide barrier coatings on plastic films and semiconductors, including the state of the art 0.25μm semiconductors.
等离子体辅助化学蒸发沉淀涂层工艺可以在比钻石化学蒸发沉淀涂层低的温度下操作。这种化学蒸发沉淀用于在塑料膜和半导体(包括人工0.25μm半导体的情况)上覆盖钻石涂层或碳化硅隔离涂层。 Altering the Surfaces改变表面
The treatments that alter the surfaces include hardening treatments, high-energy procees and special treatments.
改变表面的处理包括淬火处理、高能加工和特殊处理。
High-energy procees are relatively new surface treatment methods.They can alter the properties of surfaces without changing the dimension of the surface.Common high-energy procees, including electron beam treatment, ion implantation, and laser beam treatment, are briefly discued as follows:
高能加工是相对较新的表面处理方法。它们能在不改变表面尺寸的情况下改变表面性能。通用的高能加工包括电子束处理、离子注入和激光束处理简要讨论如下：
Electron beam treatment.Electron beam treatment alters the surface properties by rapid heating—using electron beam and rapid cooling—in the order of 106℃/see in a very shallow region, 100μm, near the surface.This technique can also be used in hardfacing to produce “surface alloys”.
电子束处理：电子束处理在靠近表面很浅(100μm)的区域通过用电子束快速加热并以106℃/秒等级快速冷却来改变表面性能。这种技术也被用于表面硬化产生“表面合金”。
Ion implantation.Ion implantation uses electron beam or plasma to impinge gas atoms to ions with sufficient energy, and embed these ions into atomic lattice of the substrate, accelerated by magnetic coils in a vacuum chamber.The mismatch between ion implant and the surface of a metal creates atomic defects that harden the surface.
离子注入：离子注入采用电子束或等离子体通过真空室内磁性线圈加速以足够的能量将气体原子撞击为离子，并把这些离子嵌入基体的原子点阵中。离子注入和金属表面之间的错配产生了硬化表面的原子瑕疵。
Laser beam treatment.Similar to electron beam treatment, laser beam treatment alters the surface properties by rapid heating and rapid cooling in a very shallow region near the surface.It can also be used in hardfacing to produce “surface alloys”.
激光束处理：与电子束处理类似，激光束处理通过在靠近表面很浅的区域快速加热和快速冷却来改变表面性能。它也可以用于表面硬化产生“表面合金”。
The results of high-energy procees are not well known or very well controlled.But the
preliminary results look promising.Further development is needed in high-energy procees, especially in implant dosages and treatment methods.
高能加工的结果不能充分地了解或很好地控制。但初步结果看来是有前途的。高能加工需要进一步的开发，特别是注入剂量和处理方法。
第十一章 Lathe 车床
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 claified 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)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 aembly 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 cro 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.
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。
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 of half nuts, which are fixed to the rear of the apron.
在切削螺旋时，动力通过丝杆提供给溜板箱上的齿轮箱。在其余车削作业中，都由光杆驱动大拖板。丝杆穿过一对固定在溜板箱后部的剖分螺母。
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 the carriage, along the bed.When the lever is disengaged, the half nuts are released and the carriage stops.当开动特定操作杆时，剖分螺母夹在一起作为单个螺母与旋转的丝杆啮合，并带动拖板沿着床身提供进给。当操作杆脱离时，剖分螺母释放同时大拖板停止运动。
On the other hand, when the feed rod is used, it supplies power to the apron through a worm gear.The latter is keyed to the feed rod and travels with the apron along the feed rod, which has a keyway extending to cover its whole length.另一方面，当使用光杆时则通过蜗轮给溜板箱提供动力。 蜗轮用键连接在光杆上，并与溜板箱一起沿光杆运动，光杆全长范围开有键槽。
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. 现代车床一般在主轴箱下装备快速变换齿轮箱，通过一系列齿轮由主轴驱动。它与光杆和丝杆连接，能容易并快速地通过简单转换适当的操作杆选择各种进给。
The quick-change gearbox is employed in plain turning, facing and thread cutting operations.Since that gearbox is linked to the spindle, the distance that the apron (and the cuttingtool) travels for each revolution of the spindle can be controlled and is referred to as the feed.快速变换齿轮箱可用于普通车削、端面切削和螺旋切削作业中。由于这种齿轮箱与主轴相连，主轴每转一圈溜板箱(和切削刀具)运动的距离能被控制，这距离就可以被认为是进给。
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 claified 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 cro 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 cro 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. 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。 Lathe Operations车床操作
In the following section, we discu the various machining operations that can be performed on a conventional engine lathe.
在下面这节中，要讨论的是能在传统普通车床上进行的各种机加工作业。
It must be borne in mind, however, that modern computerized numerically controlled lathes have more capabilities and can do other operations, such as contouring, for example.Following are conventional lathe operations.然而，必须记住现代计算机数控车床具有更多的功能并且可以进行其它操作，例如仿型。下面是传统车床的操作。
Cylindrical turning.Cylindrical turning is the simplest and the most common of all lathe operations.A single full turn of the workpiece generates 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.
圆柱面车削：圆柱面车削是所有车床操作中最简单也是最普通的。工件旋转一整圈产生一个圆心落在车床主轴上的圆；由于刀具的轴向进给运动这种动作重复许多次。
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.所以，由此产生的机加工痕迹是一条具有很小节距的螺旋线，该节距等于进给。因此机加工表面始终是圆柱形的。
The axial feed is provided by the carriage or the compound rest, either manually or automatically, whereas the depth of cut is controlled by the cro slide.
轴向进给通过大拖板或复式刀架手动或自动提供，然而切削深度则由横向滑板控制。 In roughing cuts, it is recommended that large depths of cuts (up to 0.25in.or 6mm, depending upon the workpiece material) and smaller feeds would be used.On the other hand, very fine feeds, smaller depths of cut (le than 0.05in, or 0.4mm), and high cutting speeds are preferred for finishing cuts.粗车中，推荐使用较大切削深度(根据工件材料可达0.25英寸或6毫米)和较小进给。另一方面，精车则最好采用很小的进给、较小的切削深度(小于0.05英寸或0.4毫米)和较高的切削速度。
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 cro slide, whereas the depth of cut is controlled by the carriage or compound rest.
端面车削：端面车削操作的结果是将工件整个端部表面或者像轴肩之类的中间环形表面加工平整。在端面车削操作中，进给由横向滑板提供，而切削深度则通过大拖板或复式刀架控制。
Facing can be carried out either from the periphery inward or from the center of the workpiece outward.It is obvious that the machining marks in both cases take the form of a spiral.
端面车削既可以从外表面向内切削也可以从工件中心往外切削。很明显在这两种情况下机加工痕迹都是螺线形式。
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.通常在端面车削作业时习惯于采用夹住大拖板，这是因为切削力倾向于将刀具(当然包括整个大拖板)推离工件。在大多数端面车削作业中，工件被支撑在卡盘或花盘上。
Groove cutting.In cut-off and groove-cutting operations, only cro feed of the tool is employed.The cut-off and grooving tools, which were previously discued, are employed.
开槽：在切断和开槽操作中，刀具只有横向进给。要采用前面已经讨论过的切断和开槽刀具。
Boring and internal turning.Boring and internal turning are performed on the internal surfaces by a boring bar or suitable internal cutting tools.If the initial workpiece is solid, a drilling operation must be performed first.The drilling tool is held in the tailstock, and the latter is then fed against the workpiece.
镗孔和内部车削：镗孔和内部车削通过镗杆或合适的内部切削刀具在内表面进行。如果初始工件是实心的，则必须首先进行钻孔作业。钻孔刀具安装在尾架上，然后对着工件进给。
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 cro feed is used during the machining proce 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 (le 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 cro 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 proce, 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。
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.
螺纹切削：在螺纹切削作业时，轴向进给必须保持恒定速率，这取决于工件的转速(rpm)。两者之间的关系基本上由被切削螺纹所需的节距决定。
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.
如前所述，当依靠驱动大拖板的丝杆切削螺纹时轴向进给是自动产生的。丝杆旋转一圈，大拖板就行进等于丝杆节距的一段距离。
Consequently, if the rotational 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 equal to that of the lead screw. 因此如果丝杆的旋转速度等于心轴的转速(即工件的转速)，生成切削螺纹的节距就正好等于丝杆的节距。
The pitch of the resulting thread being cut therefore always depends upon the ratio of the rotational speeds of the lead screw and the spindle: Pitch of the lead screw/ Desired pitch of workpiece=rpm of the workpiece/rpm of lead screw=spindle-to-carriage gearing ratio.所以被切削生成螺纹的节距总是取决于丝杆和心轴的转速比：丝杆的节距/工件所需节距=工件转速/丝杆转速=心轴到大拖板的传动比。
This equation is useful in determining the kinematic linkage between the lathe spindle and the lead screw and enables proper selection of the gear train between them.
这公式在决定车床心轴和丝杆之间的运动学关系时很有用，并且提供了正确挑选它们之间轮系的方法。
In thread cutting operations, the workpiece can either be held in the chuck or mounted between the two lathe centers for relatively long workpieces.The form of the tool used must exactly coincide with the profile of the thread to be cut, i.e., triangular tools must be used for triangular threads, and so on.
在螺纹切削作业中，工件既能支撑于卡盘中，对相对较长的工件也能安装在两个车床顶尖之间。使用的刀具外形必须正好与要切削螺纹的轮廓一致，即三角形刀具必须用于三角形螺纹等等。
Knurling.Knurling is mainly a forming operation in which no chips are produced.It involves preing two hardened rolls with rough filelike surfaces against the rotating workpiece to cause plastic deformation of the workpiece metal.
滚花：滚花主要是一种不产生切屑的成型操作。它使用两个带有粗锉式表面的淬火滚轮压在旋转的工件上使工件金属产生塑性变形。
Knurling is carried out to produce rough, cylindrical (or conical) 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.
滚花用于生成粗糙的圆柱(或圆锥)面，通常用来作手柄。有时表面滚花只为装饰之故；有不同的滚花图案类型可供选择。 Cutting Speeds and Feed切削速度和进给
The cutting speed, which is usually given in surface feet per minute (SFM), is the number of feet traveled in the circumferential direction by a given point on the surface (being cut) of the workpiece in 1 minute.
切削速度，通常用每分钟表面英尺给出，就是一分钟内工件(被切削)表面给定点在圆周方向上行进的英尺数。
The relationship between the surface speed and rpm can be given by the following equation:
SFM=πDN Where D=the diameter of the workpiece in feet N=the rpm 表面速度与转速之间的关系可以用下式给出：
SFM=πDN 式中
D=用英尺表示的工件直径 N=转速
The surface cutting speed is dependant primarily upon the material being machined as well as the material of the cutting tool and can be obtained from handbooks, information provided by cutting tool manufacturers, and the like.
表面切削速度主要由被切削材料和切削刀具材料决定，可以从手册、切削刀具生产商提供的资料及类似的东西上查取。
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 softer materials.For aluminum, the SFM is usually taken as 400 or above.There are also other variables that affect the optimal value of the surface cutting speed.
一般而言，SFM当机加工冷轧或低碳钢时取100，机加工较坚韧的金属时取50，而机加工较软材料时取200。对铝而言，SFM通常可取400以上。也还存在其它一些变量影响表面切削速度的最佳值。
These include the tool geometry, the type of lubricant or coolant, the feed, and the depth of cut.As soon as the cutting speed is decided upon, the rotational speed (rpm) of the spindle can be obtained as follows:
N=SFM/(πD)
其中包括刀具形状、润滑剂或冷却液的类型、进给和切削深度。切削速度一旦确定，心轴转速(rpm)就能按下式得到：
N=SFM/(πD)
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.
合适进给的选择取决于许多因素，例如所需表面光洁度、切削深度和所用刀具的几何形状。进给越小生成的光洁度越好，而在刀具与工件直接接触时进给越大则可以减少机加工时间。
Therefore, it is generally recommended to use high feeds for roughing operations and finer feeds for finishing operations.Again, recommended values for feeds, which can be taken as guidelines, are found in handbooks and in information booklets provided by cutting tool manufacturers.所以对粗车一般推荐使用较大进给，而精车则用较小进给。再者，作为指导方针的进给推荐值可以从手册和切削刀具生产商提供的资料小册子上找到。
第十二章 Drilling and Milling 钻削
Drilling and Drills钻削和钻头
Drilling involves producing through or blind holes in a workpiece by forcing a tool, which rotates around its axis, against the workpiece.
钻削就是通过迫使绕自身轴线旋转的切削刀具进入工件而在其上生成通孔或盲孔。 Consequently, the range of cutting from that axis of rotation is equal to the radius of the required hole.In practice, two symmetrical cutting edges that rotate about the same axis are employed.因此，从旋转轴线开始的切削范围等于所需孔的半径。实际上，使用的是两条围绕相同轴线旋转的对称切削刃。
Drilling operations can be carried out by using either hand drills or drilling machines.The latter differ in size and construction.Neverthele, the tool always rotates around its axis while the workpiece is kept firmly fixed.This is contrary to drilling on a lathe.
钻削作业既能采用手钻也能采用钻床来实现。钻床在尺寸和结构上虽有差别，然而始终都是切削刀具围绕自身轴线旋转、工件稳固定位的形式。这正好与在车床上钻孔相反。 Cutting Tool for Drilling Operation
In drilling operations, a cylindrical rotary-end cutting tool, called a drill, is employed.The drill can have either one or more cutting edges and corresponding flutes, which can be straight or helical.用于钻削作业的切削刀具
在钻削作业中，要用到被称为钻头的圆柱形回转端切削刀具。钻头可以有一条或多条直的或是螺旋状的切削刃以及相应的出屑槽。
The function of the flutes is to provide outlet paages for the chips generated during the drilling operation and also to allow lubricants and coolants to reach the cutting edges and the surface being machined.Following is a survey of the commonly used drills.出屑槽的功能是给钻削作业中产生的切屑提供排出通道，并允许润滑剂和冷却液到达切削刃和正在被加工的表面。下面是常用钻头的概述。
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 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。
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.
如图12.1所示，两条切削刃就是钻唇，通过凿子状边缘的楔形体连在一起。麻花钻还有两条导向边，用于作业中钻头的正确导向和定位。
The tool point angle (TPA) is formed by the two lips and is chosen based on the properties of the material to be cut.The usual TPA for commercial drills is 118°, which is appropriate for drilling low-carbon steels and cast irons.两条钻唇形成钻顶角，并根据被钻削材料的性能来选取其大小。商品化钻头的钻顶角一般为118°，这适用于钻削低碳钢和铸铁。
For harder and tougher metals, such as hardened steel, bra 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°).对于更硬更韧的金属，诸如淬火钢、黄铜和青铜，更大的钻顶角(130°或140°)才能有更好的效果。麻花钻常用的出屑槽螺旋角范围为24°到 30°。钻削紫铜或软塑料时，推荐采用更大的螺旋角(35°到45°)。
Twist drills are usually made of high-speed steel, although carbide-tipped drills are also available.The sizes of twist drills used in industrial practice range from 0.01 up to 3.25 in.(i.e., 0.25 up to 80 mm).
虽然也有硬质合金刀尖的钻头，麻花钻一般用高速钢制成。工业实际中使用的麻花钻尺寸范围为0.01到3.25英寸(即0.25到80毫米)。
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 preure 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。
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.
深孔钻有两种类型，即用于钻盲孔的中心切削深孔钻和套孔钻。后者在其中心有一圆柱形沟槽，这样能生成整体芯在钻孔作业过程中引导钻头。
Spade drills.Spade drills are used for drilling large holes of 3.5 in.(90mm) 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 grind.
扁平钻：扁平钻用于钻削3.5英寸(90毫米)或更大的大孔。其设计使得钻头成本明显节省、重量切实减轻，重量轻又使操作更方便。此外这种钻头容易磨利。 Milling and Milling Cutter铣削和铣刀
Milling is a machining proce that is carried out by means of a multiedge rotating tool known as a milling cutter.
铣削是采用被称为铣刀的多刃旋转刀具完成的机加工作业。
In this proce, 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-cutting operation.在此工艺中，金属去除是通过铣刀的旋转运动和工件的直线运动的组合实现的。铣削作业既可用于生成平面、轮廓面和螺旋面，也可用于切削螺纹和齿轮。
Each of the cutting edges of a milling cutter acts as an individual single-point cutter when it engages with the workpiece metal.Therefore, each of those cutting edges has appropriate rake and relief angles.
在铣刀切削工件金属时，铣刀的每条切削刃都象一单独的单刃刀具一样作用。所以每条切削刃都适当的前后角。
Since only a few of the cutting edges are engaged with the workpiece at a time, heavy cuts can be taken without adversely affecting the tool life.In fact, the permiible cutting speeds and feeds for milling are three to four times higher than those for turning or drilling. 由于同一时间只有部分切削刃切削工件，因此可以在对刀具寿命没有不利影响的情况下承担重型切削。事实上，铣削允许的切削速度和进给比车削或钻削高三到四倍。
Moreover, the quality of the surfaces machined by milling is generally superior to the quality of surfaces machined by turning, shaping, or drilling.此外，由铣削加工的表面质量通常优于车削、刨削或钻削加工的表面质量。
A wide variety of milling cutters is available in industry.This, together with the fact that a milling machine is a very versatile machine tool, makes the milling machine the backbone of a machining workshop.
工业上可采用的铣刀类型众多。连同铣床是极通用机床的事实，使得铣床成为机加工车间的支柱。
As far as the direction of cutter rotation and workpiece feed are concerned, milling is performed by either of the following two methods.
至于涉及到铣刀转动的方向和工件的进给，铣削可以通过下列两种方法之一进行。
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 succeively 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 proce 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.Neverthele, 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 unle 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
There is a wide variety of milling cutter shapes.Each of them is designed to perform effectively a specific milling operation.铣刀的类型
铣刀的形状类型很多。其中每种都是为有效进行特定的铣削作业而设计的。
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 survey of the commonly used types of milling cutters.通常，铣刀可以被描述为具有旋转实体形状并将切削齿安装在周边或一到两个端面上的多刃切削刀具。下面是常用铣刀类型的快速综览。
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 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。
Materials of Milling Cutters
The commonly used milling cutters are made of high-speed steel, which is generally adequate for most jobs. 铣刀的材料
普通使用的铣刀用高速钢制造，这对一般大多数工作已足够。
Milling cutters tipped with sintered carbides or cast nonferrous alloys as cutting teeth are usually employed for ma production, where heavier cuts and/or high cutting speeds are required.对大规模生产而言，因为其需要重型切削和/或高切削速度，铣刀顶端常装有烧结碳化物或有色金属碳合金作为切削齿。
第十三章 Jigs and Fixtures
Introduction
导言
It has already been stated that the workpiece must be located relative to the cutting tool, and be secured in that position.After the workpiece has been marked out, it is still neceary to position it with respect to the machine movements, and to clamp it in that position before machining is started.
已经说明了工件必须相对于切削刀具定位并确保到位。工件划线后，仍有必要将其相对于切削运动定位，并在机加工开始前把它装夹到位。
When several identical workpieces are to be produced the need to mark out each part is eliminated by the use of jigs and fixtures, but if a casting or forging is involved, a trial workpiece is marked out, to ensure that the workpiece can be produced from it, and to ensure that ribs, cores, etc.have not become misplaced.
当要加工若干同样的工件时，使用钻模和夹具可以不必在每个工件上划线；但对铸件或锻件而言，还需取一试验工件划线以保证照此加工不会将加强肋、型芯等放错位置。
Jigs and fixtures are alike in that they both incorporate devices to ensure that the workpiece is correctly located and clamped, but they differ in that jigs incorporate means of tool guiding during the actual cutting operation, and fixtures do not.
钻模和夹具的相似点是它们都把保证工件正确定位和夹紧的装置相结合，它们的不同在于钻模在实际切削作业中还能与刀具导向方法相结合，而夹具则不能。
In practice, the only cutting tools that can be guided while actually cutting are drills, reamers, and similar cutters; and so jigs are aociated with drilling operations, and fixtures with all other operations.Fixtures may incorporate means of setting the cutting tools relative to the location system.实际上，在真实切削中能被导向的切削刀具只有钻头、铰刀和类似的刀具；因此钻模用于钻削作业，而夹具用于其余作业。夹具可以与切削刀具相对定位系统装夹的方法结合在一起。
The advantages of jigs and fixtures can be summarised as follows:
1)Marking out and other measuring and setting out methods are eliminated;
2)Unskilled workers may proceed confidently and quickly in knowledge that the workpiece can be positioned correctly, and the tools guided or set;
钻模和夹具的优点可归纳如下：
1)可以省去划线和其它测量及放样程序；
2)在知道工件能正确定位、刀具能恰当导向或装夹的情况下，不熟练的工人也能自信而快速地操作；
3)the aembly of parts is facilitated, since all components will be identical within small limits, and “trying” and filing of work is eliminated;
4)The parts will be interchangeable, and if the product sold over a wide area, the problem of spare parts will be simplified.
3)由于所有零件在较小极限范围内是相同的，可以省掉工件的‘试装’和锉削，所以零件装配很方便；
4)零件具有互换性，这样如果产品在较大范围内销售的话，备件问题将简单化。
Bolt holes often have 1.5mm or even 3.0mm clearance for the bolt, and the reader may doubt the neceity of making precision jigs for such work.It must be remembered that the jigs, once made, will be used on many components, and the extra cost of an accurately made jig is spread over a large output.
螺栓孔常给螺栓留出1.5毫米或甚至3.0毫米的间隙，读者可能会怀疑为这样的工作制造精密钻模的必要性。但要记住，这种钻模一旦造好，可用于许多零部件，精确制造钻模的额外成本可分摊在大量产品上。
Furthermore, it is surprising how small errors accumulate in a mechanism during its aembly.When a clearance is specified, it is better to ensure its observance, rather than to allow carele marking out and machining to encroach upon it．
此外，这样做在装配机械装置时其累积误差之小也是令人惊讶的。在确定一个间隙时，最好能保证它的习惯要求，而不是随便划线和机加工使其超出正常的界限。
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 poible 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 poible, and using them for all location, unle other considerations mean that other location features must be used.If it is neceary, 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 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。
Definition of a Drill Jig钻模的定义
A drill jig is a device for ensuring that a hole to be drilled, tapped, or reamed in a workpiece will be machined in the proper place.
钻模是一种确保在工件正确位置进行钻孔、攻丝或铰孔加工的装置。
Basically it consists of a clamping device to hold the part in position under hardened-steel bushings through which the drill paes during the drilling operation.The drill is guided by the bushings.
它基本上由在淬硬钢衬套下将零件夹持到位的夹持装置组成，钻孔作业中钻头穿过这些衬套，通过它们来导向。
If the workpiece is of simple construction, the jig may be clamped on the workpiece.In most cases, however, the workpiece is held by the jig, and the jig is arranged so that the workpiece can be quickly inserted and as quickly removed after the machining operation is performed.如果工件结构比较简单，钻模可夹持在工件上。然而大多数情况下，工件由钻模来夹持，并且把钻模设计成能将工件迅速装入而在加工后同样能很快取出。
Jigs make it poible to drill, ream, and tap holes at much greater speeds and with greater accuracy than when the holes are produced by conventional hand methods.Another advantage is that skilled workers are not required when jigs are used.Responsibility for the accuracy of hole location is taken from the operator and given to the jig.
相对于用常规的手工方法加工孔，钻模使得钻孔、铰孔和攻丝速度快很多而且精度更高成为可能。另一个优点是采用钻模时不需要熟练工人。保证孔定位精度的责任从操作者身上转移到了钻模上。
The term jig should be used only for devices employed while drilling, reaming, or tapping holes.It is not fastened to the machine on which it is used and may be moved around on the table of the drilling machine to bring each bushing directly under the drill.Jigs physically limit and control the path of the cutting tool.
钻模这个术语只用在服务于钻孔、铰孔或攻丝的装置上。它不固定在使用它的钻床上，它能在钻床工作台上到处移动以使每个衬套都直接位于钻头下。钻模有形地限制和控制钻削刀具的路径。
If the operation includes machining operations like milling, planing, shaping, turning, etc., the term fixture should be used.A fixture holds the work during machining operations but does not contain special arrangements for guiding the cutting tool ,as drill jigs do.
如果作业还包括其它象铣削、刨削、成型、车削等机加工，则应采用夹具这一术语。夹具在机加工作业时夹持工件，但它不象钻模那样包含引导切削刀具的特殊布置。 Typical Jigs and Fixtures典型的钻模和夹具
Typical drill jig.Figure 13.2 illustrates a drilling jig for drilling four holes in the flange of a workpiece that has been completed except for the four holes.
典型的钻模：图13.2所示为一个能在某工件的法兰上钻四个孔的钻模，该工件除了这四个孔外已全部完成。
The workpiece has an accurately machined bore, and is located from the bore and the end face, from a cylindrical post.There is no need to control the rotational position about the axis of the bore, because up to the time when the holes are drilled, it is symmetrical about that axis. 此工件有一精确机加工的大孔，因此通过一圆柱体采用该孔和工件端面定位。由于直至钻这些小孔时，工件都对称于大孔轴线，所以没必要控制围绕大孔轴线回转的位置。
The four bushes used to control the drill are held in the drill plate, which, with the hand nut, is used to clamp the workpiece against the base of the fixture.四个控制钻头的衬套装在钻板里，连同手拧螺母一起用于靠着夹具基座夹持工件。
Typical milling fixture.Figure 13.3 illustrates a simple milling fixture for milling the slot in the otherwise completed workpiece shown.The workpiece is located from two of the four holes in its base, and from the underside of the base.
典型的铣削夹具：图13.3所示为一用于在图示其它工序都完成的工件上铣槽的简单铣削夹具。此工件采用其基座上四孔中的两孔和基座的底面定位。
The workpiece is clamped in position, and cutter is located against the setting block, which provides setting or cutter position and depth of cut.
工件被夹持到位，铣刀靠着提供安装或铣刀位置及切削深度的安装台定位。
The fixture must be positioned relative to the machine table, this is done by engaging the two tenons at the bottom of the fixture in the slot in the machine table.The fixture is secured to the machine table with T-bolts, also engaging in the slots in the table (Fig.13.3).夹具必须相对于铣床工作台定位，这可通过把夹具底部的两个凸榫插入工作台上的槽中来实现。夹具用T型螺栓固定于铣床工作台，同时与工作台上的槽接合(图13.3)。
Dimensioning 标注尺寸
The design of a machine includes many factors other than those of determining the loads and strees and selecting the proper materials.
机械设计除了计算载荷和应力、选择合适的材料外，还包括许多其它因素。
Before construction or manufacture can begin, it is neceary to have complete aembly and detail drawings to convey all neceary information to the shop men.The designer frequently is called upon to check the drawings before they are sent to the shop.Much experience and familiarity with manufacturing procees are needed before one can become conversant with all phases of production drawings.在建造或制造开始前，完成装配图和零件图以把必要信息传达给车间工人是必须的。在送往车间前设计者常常被召集来检查图纸。而在精通生产图纸的所有情况之前，需要有许多经验
并熟悉制造工艺。
Drawings should be carefully checked to see that the dimensioning is done in a manner that will be most convenient and understandable to the production departments.It is obvious that a drawing should be made in such a way that it has one and only one interpretation.
图纸必须仔细检查其尺寸是否按生产部门最方便易懂的方式标注。很明显图纸应该只有唯一的解释。
In particular, shop personnel should not be required to make trigonometric or other involved calculations before the production machines can be set up.
Dimensioning is an involved subject and long experience is required for its mastery.尤其是不能要求车间工人在生产机械安排前进行三角或其它复杂的计算。
尺寸标注是一项复杂的工作，要掌握它需要有丰富的经验。
Tolerances must be placed on the dimensions of a drawing to limit the permiible variations in size because it is impoible to manufacture a part exactly to a given dimension.
由于要把零件加工到正好为给定尺寸是不可能的，因此图纸的尺寸必须加上公差以限制其可允许的变化。
Although small tolerances give higher quality work and a better operating mechanism, the cost of manufacture increases rapidly as the tolerances are reduced, as indicated by the typical curve of Fig14.1.It is therefore important that the tolerances be specified at the largest values that the operating or functional considerations permit.虽然较小公差能得到较高加工质量和较好操作机构，但随着公差的减小制造成本会迅速增加，如图14.1的典型曲线所示。因此公差被定为从操作或功能考虑允许的最大值是重要的。
Tolerances may be either unilateral or bilateral.In unilateral dimensioning, one tolerance is zero, and all the variations are given by the other tolerance.In bilateral dimensioning, a mean dimension is used which extends to the midpoint of the tolerance zone with equal plus and minus variations extending each way from this dimension.
公差既可以是单向的也可以是双向的。单向标注有一公差为零，所有变化都由另一公差给定。而双向标注则采用一平均尺寸，它将公差带中点从该尺寸双向扩展为相等的正负变化范围。
The development of production procees for large-volume manufacture at low cost has been largely dependent upon interchangeability of component parts.Thus the designer must determine both the proper tolerances for the individual parts, and the correct amount of clearance or interference to permit aembly with the mating parts.
大规模低成本制造生产工艺的发展很大程度取决于组成零件的互换性。因此设计者必须确定单个零件的合适公差以及配合零件装配允许的正确间隙或过盈量。
The manner of placing tolerances on drawings depends somewhat on the kind of product or type of manufacturing proce.If the tolerance on a dimension is not specifically stated, the drawing should contain a blanket note which gives the value of the tolerance for such dimensions.在图纸上标注公差的方法相当程度上依赖于产品的性质或制造工艺的类型。如果尺寸公差没有特别注明，图纸应该包含一个给出这些尺寸公差值的普遍适用注释。
However, some companies do not use blanket notes on the supposition that if each dimension is considered individually, wider tolerances than those called for in the note could probably be specified.In any event it is very important that a drawing be free from ambiguities and be subject only to a single interpretation.然而有些公司不采用普遍适用注释，假定每个尺寸是单独被考虑的，可能会规定出比注释中
要求的更宽的公差。在任何情况下图纸不模棱两可并只服从于单一的解释是十分重要的。 Dimension and Tolerance尺寸和公差
In dimensioning a drawing, the numbers placed in the dimension lines represent dimension that are only approximate and do not represent any degree of accuracy unle so stated by the designer.
在图纸标注尺寸时，除非设计者有意标明，注在尺寸线上的数字代表的尺寸仅仅是近似的，并不代表任何精度等级。
To specify a degree of accuracy, it is neceary to add tolerance figures to the dimension.Tolerance is the amount of variation permitted in the part or the total variation allowed in a given dimension.
为了详细标明精度等级，有必要在尺寸上增加公差数字。公差是零件允许的变动量或给定尺寸允许的总变动。
A shaft might have a nominal size of 2.5in.(63.5mm), but for practical reasons this figure could not be maintained in manufacturing without great cost.Hence, a certain tolerance would be added and, if a variation of±0.003in.(±0.08mm) could be permitted, the dimension would be stated 2.500±0.003(63.5±0.08mm).一根轴可能的名义尺寸为2.5in.(63.5mm)，但由于实际原因不用大成本是不能在制造中保持这个数字的，因此要增加确定的公差。如果允许有±0.003in.(±0.08mm)的变化，则此尺寸可表达为2.500±0.003(63.5±0.08mm)。
Dimensions given close tolerances mean that the part must fit properly with some other part.Both must be given tolerances in keeping with the allowance desired, the manufacturing procees available, and the minimum cost of production and aembly that will maximize profit.
具有紧密公差的尺寸表示该零件必须恰当地与某些其它零件配合。所采用的制造工艺和使利润最大化的最小生产及装配成本都要求给定公差以保持所需允差。
Generally speaking, the cost of a part goes up as the tolerance is decreased.If a part has several or more surfaces to be machined, the cost can be exceive when little deviation is allowed from the nominal size.一般而言，零件的成本随着公差的减小而上升。如果一个零件有若干或较多表面要机加工，且几乎不允许偏离名义尺寸，则成本会超过正常合理的界限。
Allowance, which is sometimes confused with tolerance, has an altogether different meaning.It is the minimum clearance space intended between mating parts and represents the condition of tightest permiible fit.
允差，有时会跟公差混淆，但其具有完全不同的含义。它是配合零件之间最小的预期间隙空间，代表着允许的最紧配合条件。
If a shaft, size 1.498-0.003, is to fit a hole of size 1.500+0.003, the minimum size hole is 1.500 and the maximum size shaft is 1.498.Thus the allowance is 0.002 and the maximum clearance is 0.008 as based on the minimum shaft size and maximum hole dimension.
如果一根尺寸为1.498-0.003的轴与尺寸为1.500+0.003的孔配合，孔的最小尺寸为1.500而轴的最大尺寸为1.498。这样允差就是0.002，而由最小轴尺寸和最大孔尺寸形成的最大间隙为0.008。
Tolerances may be either unilateral or bilateral.Unilateral tolerance means that any variation is made in only one direction from the nominal or basic dimension.Referring to the previous example, the hole is dimensioned 1.500+0.003, which represents a unilateral tolerance.
公差可以是单向的也可以是双向的。单向公差意味着任何变动都是只从名义或基本
尺寸出发向一个方向变动的。引用前例，孔的尺寸标注为1.500+0.003，它表示了一个单向公差。
If the dimensions were given as 1.500±0.003, the tolerance would be bilateral; that is, it would vary both over and under the nominal dimension.The unilateral system permits changing the tolerance while still retaining the same allowance or type of fit.
如果尺寸标为1.500±0.003，就是双向公差；即它可以在名义尺寸之上或之下变化。单向体系允许在依然保留相同允差或配合类型的情况下改变公差。
With the bilateral system, this is not poible without also changing the nominal size dimension of one or both of the two mating parts.In ma production, where mating parts must be interchangeable, unilateral tolerances are customary.To have an interference or force fit between mating parts, the tolerances must be such as to create a zero or negative allowance.而双向体系在不同时改变一个或两个配合零件名义尺寸的情况下，这是不可能做到的。大规模生产中配合零件必须能互换，单向公差是经常遇到的。为了使配合零件之间具有过盈或强制配合，公差必须产生零或负允差。
Tolerances, Limits and Fits公差、极限和配合
The drawing must be a true and complete statement of the designer’s requirements expreed in such a way that the part is convenient to manufacture.
图纸必须按方便制造零件的方式将设计者的要求真实和完整地表达出来。
Every dimension neceary to define the product must be stated once only and not repeated in different views.Dimensions relating to one particular feature, such as the position and size of a hole, should, where poible, appear on the same view.对每一描述产品所需的尺寸都只须标注一次而不必在不同的视图中重复。有关同一特性的尺寸，诸如孔的位置和大小，如果可能应出现在同一视图上
There should be no more dimensions than are absolutely neceary, and no feature should be located by more than one dimension in any direction.
除绝对需要的尺寸外，不应该有更多的尺寸；而在任意方向上，只能在一个尺寸上标注特性要求。
It may be neceary occasionally to give an auxiliary dimension for reference, poibly for inspection.When this is so, the dimension should be enclosed in a bracket and marked for reference.Such dimensions are not governed by general tolerances.偶尔也可能为了检查而必须给出供参考的辅助尺寸。在这种情况下，尺寸应该用括号括起来，以便参考。这样的尺寸不受通用公差控制。
Dimensions that affect the function of the part should always be specified and not left as the sum or difference of other dimensions.
影响零件功能的尺寸总是应该标注的而不要留作其它尺寸的和或差。
If this is not done, the total permiible variation on that dimension will form the sum or difference of the other dimensions and their tolerances, and this will result in these tolerances having to be made unnecearily tight.The overall dimension should always appear.如果不是这样，那尺寸允许的总的变化将形成其它尺寸及它们的公差的和或差，这会导致这些公差不得不定得过紧。总尺寸一般应该标注。
All dimensions must be governed by the general tolerance on the drawing unle otherwise stated.Usually, such a tolerance will be governed by the magnitude of the dimension.Specific tolerances must always be stated on dimensions affecting function or interchangeability.
除非另行说明，所有尺寸都必须受图上的通用公差控制。一般这样的公差受到尺寸量值的控制。在影响功能或互换性的尺寸上必须标注专门的公差。
A system of tolerances is neceary to allow for the variations in accuracy that are bound to occur during manufacture, and still provide for interchangeability and correct function of the part.
为了允许在制造过程中必然会发生的精度变化，并提供零件的互换性和正确功能，一个公差系统是必需的。
A tolerance is the difference in a dimension in order to allow for unavoidable imperfections in workmanship.The tolerance range will depend on the accuracy of the manufacturing organisation, the machining proce and the magnitude of the dimension.
公差是为了允许工艺上不可避免缺陷而存在的尺寸上的不同。公差范围取决于制造机构的精度、机加工过程和尺寸的量值。
The greater the tolerance range, the cheaper the manufacturing proce.A bilateral tolerance is one where the tolerance range is disposed on both sides of the nominal dimension.A unilateral tolerance is one where the tolerance zone is on one side only of the nominal dimension, in which case the nominal dimension may form one of the limits.
公差范围越大，则制造过程的成本就越低。双向公差是在公称尺寸两侧都有公差带的公差。单向公差是仅在公称尺寸一侧有公差带的公差，在这种情况下公称尺寸成了两个极限中的一个。
Limits are the extreme dimensions of the tolerance zone.For example, nominal dimension
30mm tolerance
limits
极限是公差带的极限尺寸。例如公称尺寸30毫米 公差
极限
Fits depend on the relationship between the tolerance zones of two mating parts, and may be broadly claified into a clearance fit with positive allowance, a transition fit where the allowance may be either positive or negative (clearance or interference), an interference fit where the allowance is always negative.
配合取决于两配合零件公差带之间的关系，并且可以概括地分为具有正允差的间隙配合，允差可以是正或负的过渡配合和总是负允差的过盈配合。 Type of Limits and Fits极限和配合的类型
The ISO System of Limits and Fits, widely used in a number of leading metric countries, is considerably more complex than the ANSI system.
在一些最主要采用公制的国家中广泛使用的ISO的极限和配合系统，比ANSI的极限和配合系统要复杂得多。
In this system, each part has a basic size.Each limit of size of a part, high and low, is defined by its deviation from the basic size, the magnitude and sign being obtained by subtracting the basic size from the limit in question.The difference between the two limits of size of a part is called the tolerance, an absolute amount without sign.
在这个系统中，每个零件都有基本尺寸。零件尺寸的每一极限，不管大小，都通过对基本尺寸的偏差来定义；其量值和符号由正被讨论的极限减去基本尺寸得到。零件尺寸的两个极限之差称为公差，这是一个没有符号的绝对量值。
There are three claes of fits: 1) clearance fits, 2) transition fits (the aembly may have either clearance or interference), and 3) interference fits.
存在三种配合：1)间隙配合，2)过渡配合(装配后可以有间隙或过盈)，和3)过盈配合。
Either a shaft-basis system or a hole-basis system may be used.For any given basic size, a range of tolerances and deviations may be specified with respect to the line of zero deviation,
called the zero line.
基轴制或基孔制均可采用。对任何给定的基本尺寸，公差范围和偏差可以相对于被称为零线的零偏差线来确定。
The tolerance is a function of the basic size and is designated by a number symbol, called the grade—thus the tolerance grade.公差是基本尺寸的函数 并通过一个被称为等级的数字符号标明—即公差等级。
The position of the tolerance with respect to the zero line also a function of the basic size—is indicated by a letter symbol (or two letters), a capital letter for holes and a lowercase letter for shafts.Thus the specification for a hole and shaft having a basic size of 45 mm might be 45H8/g7.公差相对于零线的位置同样为基本尺寸的函数通过一个或两个字母符号表达，大写字母表示孔而小写字母表示轴。这样基本尺寸为45毫米的一个孔和轴配合规格可能是45H8/g7。
Twenty standard grades of tolerances are provided, called IT01, IT0, IT1~18, providing numerical values for each nominal diameter, in arbitrary steps up to 500mm (for example 0~3, 3~6,6~10, ......, 400~500 mm).
ISO规定了二十种标准的公差等级，称之为IT01，IT0，IT1~18，给在直至500毫米强行分段(例如0~3，3~6，6~10, ......, 400~500毫米)中的公称直径提供具体数值。
The value of the tolerance unit, i, for grades 5~16 isWhere i is in microns and D in millimeters.对5～16级而言，公差单位i的值可用下式计算这里i的单位是微米，而D的单位是毫米。
Standard shaft and hole deviations similarly are provided by sets of formulas, however, for practical application, both tolerances and deviations are provided in three sets of rather complex tables.
标准的轴和孔偏差同样都由若干公式提供；然而对实际应用，公差和偏差都在三张相当复杂的表格中规定了。
Additional tables give the values for basic sizes above 500 mm and for “Commonly Used Shafts and Holes” in two categories—“General Purpose” and “Fine Mechanisms and Horology”.
对基本尺寸大于500毫米和在“一般用途”和“精密机械和钟表”两个类别中的“常用的轴和孔”而言，由附加的表格给出数值
