机械加工工艺夹具类毕业钻削与镗削外文文献翻译@中英文翻译@外文翻译

外文翻译 专 业 机械设计制造及其自动化 学 生 姓 名 闻 志 祥 班 级 B 机 制 023 学 号 0210110316 指 导 教 师 刘 道 标 1 钻削与镗削 Addison-Wesley pub.Co. 闻志祥 译 摘要 ：通过驱动刀具 能在工件上钻出通孔或盲孔，钻刀是正对着工件绕着自己的轴线旋转。当然，刀具从其轴线向外的切削距离应和需加工的孔的半径相等。在实际生产中，是采用关于同一轴线对称的两切削刀刃的刀具。钻削既可被应用于手工也可用于钻床中。钻床在尺寸和结构上有所不同。然而，当工件被牢固地安装好后，钻刀总是绕着自己的轴线旋转。这是和在车床上钻孔是相反的。镗孔是扩大以前钻削或镗削好了的孔。镗孔能够消除钻空加工时孔所产生的偏心，使孔扩大到需铰削的尺寸。下面是对钻削、钻床分类和镗孔的简要介绍。 关键词 ：钻削、镗削、钻床、钻削刀具、镗刀、钻床的 分类 钻削刀具 在钻削操作中，采用的是一种柱形的螺旋式刀具，被称之为钻刀。钻刀有一条或两条切削刃和相应的出屑槽，出屑槽呈直线或螺旋线形。出屑槽的作用是为在钻削过程中产生的切屑提供一个通道，同时也是便于润滑剂和冷却剂到达钻刀的切削刃和工件的被加工表面。以下是普通刀具的概括论述： 图 4.1 麻花钻 。麻花钻是最普通的一类钻刀。麻花钻有两条切削刃和两条螺旋线形的出屑槽，出屑槽连续地围绕分布在整个钻体上（如图 4.1）。钻刀除了钻体部分，还有钻颈和钻柄，钻柄可以是圆柱形，也可以是 锥行。在后者的情况下，钻柄是通过柄舌钻体 顶角 楔边 死顶尖 出屑槽 螺旋角 颈部 柄部 出屑槽 刀刃 刃带 后刃面 出屑槽 刀刃 刃带 柄舌 2 的楔形作用安装在主轴的锥形钻套中，柄舌是安装在主轴钻套的狭槽中，这样钻刀和主轴形成一个整体来传递旋转运动。在另一方面，圆柱形钻柄是被安装在钻夹头里，然后，以安装锥形钻柄的方法将其安装进主轴的钻套中。 从图 4.1 可以看出，两条切削边被称为刀刃，两条切削刃是通过楔子连接在一起。麻花钻还有两条刃带，其能在钻削操作中对刀具起正确的导向和定位的作用。两条刀刃形成钻刀的顶角，顶角大小的选择是依据被加工材料的特性。工业生产中经常使用的钻刀的顶角是 118，其适合钻削低碳钢和铸铁。对于 硬度和刚度较高的金属，譬如，硬刚，黄铜和青铜，宜选用稍大顶角（ 130或 140）的钻刀。常用麻花钻的出屑槽的螺旋角是范围是在 24 -30之间。当在钻削铜或软塑材料时，推荐使用螺旋角较大的刀具（ 35 -45之间）。 图 4.2 空心钻 。 空心钻是由倒棱，钻体，钻颈和钻柄组成，如图 4.2 所示。此类的空心钻有三条或四条出屑槽和相应数量的刃带保证良好的导向来获得高的加工精度 。从图 4.2 还可以看出空心钻有一平断，倒棱可能有三条或四条切削边，或称为刀刃，顶角可在 90-120 范围内变化。空心钻是用来扩 大先前已有的孔，它不是用来钻削新的孔的。空心钻有高的生产率，高的加工精度和能钻削出高质量的表面的特性。 枪孔钻 。枪孔钻是用来加工深孔的。所有的枪孔钻的出屑槽都是直的，只有一单条切削刃。在枪钻的钻体上有一个孔，其起着导管的作用，冷却剂在较的压力下通过该孔流到枪钻的顶尖部位。 现有两种枪钻，即，用来加工盲孔的中心钻和套筒钻。套筒钻的中心有一个圆柱形孔，钻孔时可在工件上形成一个芯子，当钻头连续进给进行钻孔时，芯子对钻起导向作用。 平钻 。平钻是用于钻削大于 7/2 英寸的孔（ 90mm）乃至更大的孔。该类的钻易于磨削。 镗刀 镗孔是扩大以前钻削或镗削好了的孔。镗孔能够消除钻空加工时孔所产生的偏顶角 倒棱 钻体 钻颈 钻柄 3 心，使孔扩大到需铰削的尺寸。 平底扩孔是指扩大一个钻孔的末端。这个扩大的孔的底部是平的，它与原来的孔是同轴的。刀具与导向销一起使用，导向销装进已钻好的孔中，用于切削刃对中。平底扩孔主要用于在上面安装螺栓下面安装螺钉的孔的加工。在一个已加工好的孔上加工一个小的平面，该面称之为刮孔平面。在粗糙的表面上为螺栓提供平滑的沉头座的操作是很普遍的。如果把一个已加工控切成斜边以便适合一个平底螺栓的圆锥座，该操作称为锪锥面。 刀具用于卧式镗床或是被安 装在一个大型杆上或是作一个镗前头，它们依次排布在 机床的主轴上。绝大多数镗孔操作是使用具有一个单齿的镗刀，如图 4.3 所示，因为他们易于安装和维修。镗杆的作用是将来机床自轴的动力传递到刀具上和保持在切削过程中的刚性，在加工过程中，工件通常不动，刀具在孔中作旋转进给运动。如图所示，通常需给镗杆提供附加支撑。镗杆必须足够的长以达到末端支撑和为机床操作提供一定的纵向空间。 图 4.3 在铣床、坐标镗床、或钻床上进行精密镗削时，有必要使用一种带有千分尺调整的工具。这种工具安装在刀具头上并作旋转运动 。因此任何孔径的增加必须通过调整工具半径来获得。图 4.3b 所示的是最常见的组合式双镗刀布置形式 ,他包括两个相对的刀具夹在沟槽中。螺柱是用来在指定位置锁紧刀具和调整他们的位置。整体装进一个矩形狭槽中 ,且锁在固定位置。刀具固定在滑行刀架里 ,且与顶尖成一条直线。刀具的精度取决与刀具车间的全体人员而不是操作者 . 端部支承 镗杆 工件 主轴 床头箱 镗杆 镗刀 镗刀 工作台 4 通常用于小型机床譬如车床的镗刀是单齿镗刀，他是被以其能进入孔内的方式支承着。图 4.4a 所示刀具的末端事实锻造的，然后通过磨削成型。它是安装在一个单独的支承杆上，该支承杆是安装在车床的刀架上。对于转塔车 床所用的是类似于图4.4b 所示的刀具，只是刀杆稍有不同。刀具的修改是镗杆部分，如图 4.4c 所示，它被设计成在镗杆的末端拥有一个小型高速钢刀具。镗杆的刚度强，其长度可根据孔的长度作相应的调整。尽管这些刀具的间隙、斜度和切削角应该接近那些在车床操作中推荐使用的相近，但如果孔较小的话，这些角度是不能使用的。 在加工工件中，普遍使用多切削刃的镗刀。如图 4.4f，这些表面类似筒形绞刀的刀具，但具有镶齿铣刀，它们被调整成补偿磨损和直径变化。这种类型的镗刀比单刃刀具有较长的寿命，因此在加工中更经济。如图 4.4e 所示的带 有导向销的以保证同轴度的平底扩孔刀具是用来扩大孔的末端。 钻床的分类 便携式的小机床上可实现钻削操作，一般的机床上也可以实现钻削操作。一般的机床在形状和尺寸上不同于便携式小机床，但它们也有共同的特征。例如，它们都拥有一根或更多根的麻花钻，当在加工以被固定装好了的工件时，每根麻花钻绕着自己的轴作旋转运动。这和在车床上工件被夹紧并随着卡盘作旋转运动而进行的钻削是相反的。下面是对一些普通式钻床的概述。 台式钻床 。台式钻床通常是被放在工作台上的普通加工用途的小型机床。这种钻床包括一个动力来源的电动机，动力是通过滑轮 和皮带传递到装有刀具的主轴上。进给运动是通过降低操纵杆，由操纵杆带动主轴的下降（或上升）来实现的。台钻的主轴在套筒内自由旋转（套筒由操纵杆通过齿轮齿条系统驱动，但不随主轴一起旋转）。 加工工件时，工件是被放在机床的工作台上，有时需要一个特殊的花钳来固定。被加工工件的最大厚度是受机床主轴与工作台之间的间隙限制。 图 4.4 5 立式钻床 。立式钻床可被用于轻度、中等、甚至相对重负荷强度的工作，这主要取决于立式钻床的尺寸。 立式钻床与台式钻床基本相似，主要的不同点是里是立式钻床的底座上装有一较长的圆柱形支柱。在支柱上附加安装了一 个可以锁定在任一想要高度的滑动工作台。当立式钻床用于中等强度的工作时，其所需的动力要比台式钻床的多。 在立式钻床里有比较的的钻床。因此，这大的钻床有一个箱柱和较高的动力，以此满足重负荷。此外，它是采用齿轮箱为主轴提供不同的旋转速度和轴向进给量，通过齿轮箱可以预先设置任何想要的主轴转速和进给速率。 多轴钻床 。多轴钻床的结构坚固，其工作时需要很强的动力，每台多轴钻床能同时钻削很多孔。为满足加工要求，不同的刀具是可以调整的，同时根据需要，整个床头箱部分（带有主轴和刀具）是可以倾斜的。 这类的钻床主要用于批量生产且 拥有很多孔的零件的加工。例如汽缸体。 排式钻床 。当几个独立的钻头（每个都有一个单独主轴）排列在一个单独的普通的工作台上，此时，该机床被称之为排式钻床。这种机床特别地适用于几种需连续进行的操作。 摇臂钻床 。摇臂钻床，特别地适合那些不便于安装在立式钻床上的大型和重型工件进行钻孔。在图 4.5 可以看出，摇臂钻床有一安装在底座上的立柱。摇臂钻床的摇臂带着钻床的床头箱主轴和刀具移动，该摇臂能够沿立柱上升或下降，并可以锁紧在任一所需的位置上。床头箱沿着摇臂滑动并使主轴作旋转运动和轴向进给运动。此外，电动机 立柱 底座 主轴 摇臂 钻床的床头箱 丝杆 图 4.5 6 摇臂能够摆动，因此刀具可移动到圆柱坐标系统的任一位置。 转塔钻床 。归属于转塔钻床类的机床，或是半自动或是全自动控制的。转塔机床的一个普遍的设计特征是用转塔代替原来机床的主轴，转塔上装有几把钻削、镗削 和螺纹切削刀具。因此，几种连续的操作只需要在一次初安装下就可以完成，在两种操作之间不需要再次装夹工件。 如今，由数字或计算机控制系统控制的自动转塔钻床是相当的普遍了。在这种情况下，人的工作只是对工件进行初安装和对其进行监控。这类机床就空间要求（机床的物理尺寸）和工件装夹次数而言比排式钻床有优越性。 长孔钻床 。长 孔钻床是一类特殊的被用作钻削长孔的机床，譬如，枪管的长孔就是用此类机床加工。通常长孔钻在使用时对工件的进给速度是较慢的。这类机床在工作时，工件作旋转运动，而刀具不作旋转运动。长孔钻床有立式结构也有卧式结构。然而，这两种结构的共同特征是在钻削过程中工件的精确导向和刚性支承。 坐标镗床 。这类机床是为获得高的精确性和精密性而特别设计的。这类机床不但钻孔而且能够给孔定位，因为工作台的运动由电子测量装置监控着。 7 DRILLING AND BORING Addison-Wesley pub.Co. Abstract: Drilling involves producing through or blind holes in a workpiece by forcing a tool, which rotates around its axis, against the workpiece. Consequently, the range of cutting from that axis of rotation is equal to the radius of the required hole. In practice, two symmetrical cutting edges that rotate about the same axis are employ. Drilling operations can be carried out by using either hand drills or drilling machine. The latter differ in size and construction. Nevertheless, the tool always rotates around its axis while the workpiece is kept firmly fixed. This is contrary to drilling on a lathe. Boring is enlarging holes previously drilled or bored. Drilled holes are frequently bored to eliminate any possible eccentricity and to enlarge the hole to a reaming size. Following is a survey of drilling, drilling machine tool and boring. Keyword: drilling boring drilling machine tool classification of drilling machine cutting tool for drilling operations cutting tool for boring operations CUTTING TOOL FOR DRILLING OPERATIONS 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. The function of the flutes is to provide outlet passages for the chips generated during the drilling operation and also to allow lubricants and coolants to reach the 8 cutting edges and the surface being machined. Following is a survey of the commonly used drills. Twist drill. The twist drill is the most common type of drill. It has two cutting edges and two helical flutes that continue over the length of the drill body, as shown in Fig.4.1. The drill also consists of a neck and a shank that can be either straight or tapered. In the latter case, the shank is fitted by the wedge action into the tapered socket of the spindle and has a tang, which goes into a slot in the spindle socket, thus acting as a solid means for transmitting rotation. On the other hand, straight-shank drills are held in a drill chuck that is, in turn, fitted into the spindle socket in the same way as tapered shank drills. Fig.4.1 The twist drill As can be seen in Fig.4.1, the two cutting edges are referred to as the lips, and are connected together by a wedge, which is a chisel-like edge. The twist drill also has two margins, which enable proper guidance and locating of the drill while it is in operation. The tool point angle (TPA) is formed by the two lips and is chosen based on the properties of the material to be cut. The usual TAP for commercial drills is 118, which is appropriate for drilling low-carbon steels and cast irons. For harder and tougher metals, such as hardened steel, brass and bronze, larger TAPs (130or 140) give better performance. The helix angle of the flutes of the commonly used twist drills 9 ranges between 24 and 30 . When drilling copper or soft plastics, higher values for the helix angle are recommended (between35 and 45). Fig.4.2 The core drill Core drills. A core drill consists of the chamfer, body, neck, and shank, as shown in Fig.4.2.This type of drill may have either three or four flutes and an equal number of margins, which ensure superior guidance, thus resulting in high machining accuracy. It can also be seen in Fig.4.2 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 . Core drills are employed for enlarging previously made holes and not for originating holes. This types of drill is characterized by greater productivity, high machining accuracy, and superior quality of the drilled surfaces. Gun drills. Gun drills are used for drilling deep holes. All gun drills are straight-fluted, and each had a single cutting edge. A hole in the body acts as a conduit to transmit coolant under considerable pressure to the tip of the drill. There are two kinds of gun drills, namely, the center-cut dill used for drilling blind holes and the trepanning drill. The latter has a cylindrical groove at its center, thus generating a solid core, which guides the tool as it proceeds during the drilling operation. Spade drill. Spade drills are used for drilling large holes of 7/2in. (90mm) or more. Their which 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. BORING TOOLS Boring is enlarging holes previously drilled or bored. Drilled holes are 10 frequently bored to eliminate any possible eccentricity and to enlarge the hole to a reaming size. Counterboring is enlarging one end of a dilled hole. The enlarged hole, which is concentric with the original one, is flat on the bottom. The tool is provided with a pilot pin that fits into the drilled hole to center the cutting edges. Counterboring is used principally to set bolt heads and nuts below the surface. To finish off a small surface around a drilled hole is known as spot facing. This is a customary practice on tough surface to provide smooth seats for bolt heads. If the top of a drilled hole is beveled to accommodate the conical seat pf a flat-head screw, the operation is called countersinking. Fig.4.3 Tools used in horizontal boring machines are mounted in either a heavy bar or a boring head, which in turn is connected to the main spindle of the machine. Most boring operations use a single-point cutter as shown in Fig.4.3, because they are simple to set up and maintain. The bar serves to transmit power from the machine spindle to the cutter as well as to hold it rigidly during the cutting operation. The workpiece is normally stationary and the rotating cutter is fed through the hole. It is often necessary to provide additional support for the bar as shown in the figure. The bar must be long enough to reach the end support and also must provide the necessary longitudinal traverse for the machining operation. For precision boring work on milling machines, jig bore, or drill presses, it is necessary to use a tool having micrometer adjustment. Such tools are held in a cutter head and rotate. Hence, any increase in hole size must be 11 obtained by adjusting the tool radially from its center. The most popular double-cutter arrangement is the block type shown in Fig.4.3b, which consists of two opposing cutters resting in grooves on the block. Screws are provided to lock the cutters in position as well as to adjust them. The entire assembly fits into a rectangular slot in the cutters in position as well as to adjust them. The entire assembly fits into a rectangular slot in the bar and is keyed in place. Cutters are ground while assembled in the block and are held in alignment by the center holes provided. The responsibility for tool accuracy and setup belongs to the toolroom personnel rather than the operator. Fig.4.4 Types of boring tools The boring tool commonly use in small machines such as lathes is a single -pointed tool, supported in a manner that permits its entry into a hole. This tool, shown in Fig.4.4a is forged at the end and then ground to shape. It is supported in a separate holder that fits into a lathe tool post. For turret lathes, slightly different holders and forged tools similar to the one shown in Fig.4.4b are used. A modification of this tool is the boring bar shown in Fig.4.4c, which is designed to hold a small high-speed steel tool bit at the end. The bar supporting the tool is rigid and may be adjusted according to the hole length. Although the clearance, rake, and cutting angles cannot be used if the tools should be similar to those recommended for lathe work, these angles cannot be used if the holes are small. In production work, boring cutters with multiple cutting edges are widely used. These cutters, shown in Fig.4.4f resemble shell reamers in appearance 12 but are usually provided with inserted-tooth cutters that may be adjusted radially to compensate for wear and variations of diameter. Boring tools of this type have longer life than single-pointed tools and hence are more economical for production jobs. The counterboring tool shown in Fig.4.4e provided with pilots to ensure concentric diameters. Is designed to recess or enlarge one end of a hole. CLASSIFICATION OF DRILLING MACHINES Drilling operations can be carried out by employing either portable small machines or appropriate machine tools. The latter differ in shape and size, although they have common features. For instance, they all involve one or more twist drills, each rotating around its own axis while the work piece is kept firmly fixed. This is contrary to the drilling operation on a lathe, where the work piece is held in and rotates with the chuck,. Following is a survey of the commonly used types of drilling machines. Beach-type drilling machines. Beach-type drilling machines are general-purpose, small machine tools that are usually placed on benches. This type of drilling machine includes an electric motor as the source of motion, which is transmitted via pulleys and belts to the spindle, where the tool is mounted. The feed is manually generated by lowering a lever handle, which is designed to lower (or raise) the spindle. The latter rotates freely inside a sleeve (which is actuated by the lever through a rackpinion system but does mot rotate with the spindle ). The workpiece is mounted on the machine table, although a special vise is sometimes used to hold, the workpiece. The maximum height of a workpiece to be machined is limited by the maximum gap between the spindle and the machine table. Upright drilling machines. Depending upon the size, upright drilling machine tools can be used for light, medium, and even relatively heavy jobs. It is basically similar to bench-type machines, the main difference being a longer cylindrical column fixed to the basic. Along that column is an 13 additional, sliding table for fixing the workpiece which can be locked in position at any desired height. The power required for this type is more than that for bench-type drilling machines, since this type is employed in performing medium-duty job. There are also large drilling machines of the upright type. In this case the machine has a box column and a higher power to deal with large jobs. Moreover, gear boxes are employed to provide different rotational spindle speeds as well as the axial feed motion, which can be preset at any desired rate. Multispindle drilling machines. Multispindle drilling machines have sturdy construction and require high power； each is capable of drilling many holes simultaneously. The positions of the different tools (spindles)can be adjusted as desired. Also, the whole head (which carries the spindles and tools) can sometimes be titled, as required. This type of drilling machine is used mainly for mass production in jobs having many holes, such as cylinder blocks. Gang drilling machines. When several separate heads (each with a single spindle)are arranged on a single common table, the machine tool is then referred to as a gang drilling machine. This type of machine tool is particularly suitable where several operations are to be performed in succession. Fig.4.5 A Sketch of radial drill. 14 Radial drill. A radial drill is particularly suitable for drilling holes in large and heavy workpiece that are inconvenient to mount on the table of an upright drilling machine. As you can see in Fig.4.5, a radial drilling machine has a main column, which is fixed to base. The cantilever guide arm, which carries the drilling head spindle and tool, can be raised or lowered along the column and clamped at any desired position. The drill head slides along the arm and provides rotary motion and axial feed motion. Again, the cantilever guide arm can be swung, thus enabling the tool to be moved in all directions according to a cylindrical coordinate system. Turret drilling machines. Machines tools that belong to the turret drilling machines are either semi-or fully automatic. A common design feature is that the main spindle is replaced by a turret, which carries several drilling, boring, reaming, and threading tools. Consequently, several successive operations can be carried out with only a single initial setup and without the need for setting up the w