part1_unit12drilling and milling

Name： LI Zisheng School： Manufacturing Telephone： 13890176029 Email: lizishengswust.edu.cn,Unit 12 Drilling and Milling,Specialized English (Part 1),Paragraph 1,1.Drilling involves producing through or blind holes in a workpiece by forcing a tool, which rotates around its axis, against the workpiece. 钻是利用绕轴旋转的钻头在工件上生成通孔或盲孔的加工工艺。 2.Consequently, the range of cutting from that axis of rotation is equal to the radius of required hole. 因此，旋转轴的切削范围就等于所钻孔的半径。 3.In practice, two symmetrical cutting edges that rotate about the same axis are employed. 实际上是利用绕同一轴的旋转的两个对称切削刃(棱边)来进行加工的。,Paragraph 2,1.Drilling operations can be carried out by using either hand drills or drilling machines. The latter differ in size and construction. 钻加工有手钻和钻床两种方式。钻床的大小和结构各不相同。 2.Nevertheless, the tool always rotates around its axis while the workpiece is kept firmly fixed. This is contrary to drilling on a lathe. 然而，钻床加工中钻头总是绕轴旋转而工件保持固定。这与车床上的钻加工相反。,Paragraph 3,1.In drilling operations, a cylindrical rotary-end cutting tool, called a drill, is employed. 在钻加工中，采用了一种圆柱形的、端面旋转的刀具，称为钻头。 2.The drill can have either one or more cutting edges and corresponding flutes, which can be straight or helical. 钻头可能有一个或多个切削刃(棱边)以及直立的或螺旋状的出屑槽。,Paragraph 3,3.The function of the flutes is to provide outlet passages for the chips generated during the drilling operations and also to allow lubricants and coolants to reach the cutting edges and the surface being machined. Following is a survey of the common used drills. 出屑槽的作用就是为钻加工过程中产生的碎片提供出口通道，同时允许润滑剂和冷却剂流到切削刃和被加工的工件表面上。下面是平常所使用钻头的概况。,Paragraph 4,1.Twist drill. The twist drill is the most common type of drill. 螺旋钻(麻花钻).麻花钻是最常用的钻头。 2.It has two cutting edges and two helical flutes that continue over the length of the drill body, as shown in Fig.12.1. 麻花钻具有两个切削刃(棱边)以及两道沿钻体的螺旋槽，见图12.1。 3.The drill also consists of a neck and a shank that can be either straight or tapered. 钻头也包括一个钻颈和一个可为直柄或锥柄的柄部。,Paragraph 4,4.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. 对于后者，柄部可用斜铁将其固定在主轴的锥形孔中，柄部还有一个柄脚，柄脚插入到主轴锥形孔的插槽中，这样就可以可靠的方式传递扭矩。,Paragraph 4,5.On the other hand, straight-shank drills are held in a drill chunk that is, in turn, fitted into the spindle socket in the same way as tapered shank drills. 另一方面，直柄钻被固定到钻夹中，同理，钻夹以与锥柄钻相同的方式固定到主轴孔中。,Paragraph 5,1.As can be seen in Fig.12.1, the two cutting edges referred to as the lips, and are connected together by a wedge, which is a chisel-like edge. 从图12.1可以看出，两个切削刃被称作为刀刃，通过契子，一个象凿子似的边，连接在一起。 2.The twist drill also has two margins, which enable proper guidance and locating of drill while it is in operation. 麻花钻还有两个刃带，在加工过程中可正确引导和定位钻头。,Paragraph 5,3.The tool point angle (TPA) is formed by the two lips and is chosen based on the properties of the material to be cut. 刀刃脚是通过两道刀刃形成的，并且它的选择也是基于被钻削的材料有关。 4.The usual TPA for commercial drills is 118。,which is appropriate for drilling low-carbon steels and cast irons. 商品化钻头的通用TPA是118度，适合钻低碳钢和铸铁。,Paragraph 5,5.For harder and tougher metals, such as hardened steel, brass and bronze, larger TPAs(130。or 140。)give better performance. 对于硬度更大和忍度更高的金属,比如硬化钢、黄铜和青铜，较大的TPAS(130度或140度)会得到更好的钻削效果。 6.The helix angle of the flutes of the commonly used twist drills ranges between 24。and 30。. 平常使用麻花钻的出屑槽的螺旋角范围在24度至30度之间。,Paragraph 5,7.When drilling copper or soft plastics, higher values for the helix angle are recommended (between 35。to 45。) 当在对铜和软塑料进行加工时，推荐使用高一些的螺旋角(35度至45度)。,Paragraph 6,1.Twist drills are usually made of high-speed steel, although carbide-tipped drills are also available. The size of twist drills used in industrial range from 0.01 up to 3.25 in. (i.e., 0.25 up to 80 mm). 尽管在加工中有用硬质合金镶片构成的钻头，但麻花钻通常由高速钢作成。在工业生产实践中，麻花钻的尺寸大小通常在0.01至3.25英寸的范围内。(即是0.25到80毫米)。,Paragraph 7,1.Core drills. A core drill consists of the chamfer, body, neck, and shank, as shown in Fig.12.2. 扩孔钻：从图12.2可看出，扩孔钻由倒角、钻体、钻颈和钻柄组成。 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. 这种类型的钻具有三个或四个出屑槽以及相同数量的刃带，这些可确保准确的导向，从而获得较高的机加工精度。,Paragraph 7,3.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 between 90。 and 120。 从图12.2还可看出，扩孔钻有一个扁形的柄脚。倒角又三四个切削刃或刀刃，刀刃角从90度到120度大小不等。 4.Core drills are employed for enlarging previously made holes and not for originating holes. 扩孔钻是用来扩孔而不是用来钻孔的。,Paragraph 7,5.This type of drill is characterized by greater productivity, high machining accuracy, and superior quality of the drilled surfaces. 这种类型的钻具有高效率、高机加精度和好的表面质量。,Paragraph 8,1.Gun drills. Gun drills are used for drilling leap holes. All gun drills are straight-flutes, and each has a single cutting edge. 深孔钻：深孔钻是用来钻削深孔。所有的深孔钻都是直槽并有一个单刃。 2.A hole in the body acts as a conduit to transmit coolant under considerable