些常用的钻头。
Twist Drill 麻花钻
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. The drill also consists of a neck and a shank that can be either straight or tapered.
麻花钻是最常用的钻。在钻身上有两个切削刃和两个螺旋形排削槽。还包括一个颈和一个柄，他们既可以是锥形的也可以是直的。
carbide tipped drill硬质工具刀头钻
Most of drills are made of high-speed steel. However, for machining hard materials as well as for large volume production, carbide tipped drill are available. As shown in Fig.24.1, the carbide tips of suitable geometry适当的几何学 are clamped夹紧 to the end of the tool to act as the cutting edges.
大部分的钻是高速钢做的。然而当材料是硬质材料或者是大批量生产时，硬质工具刀头钻常常更加适合。如图所示，适当的形状的硬质钻被夹紧到工具的末端作为刀具。
Core Drills中心钻，扩孔钻 A core drill consists of the chamfer凹槽, body, neck, and shank. A core drill has flat end. The chamfer can have three or four cutting edges. Core drills are employed for enlarging放大 previously之前 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
中心钻包括凹槽，钻身，颈部和柄部。中心钻是平头的。凹槽可以有三到四个切割刃。扩孔钻是用来扩大之前已有的孔，而不能自己钻原始孔。这类钻的特点是生产效率高，机器精度高，孔的表面质量好。
Other Types of Drilling Operations其他类型的钻
In addition to conventional drilling, there are other operations that are involved in the production of holes in the industrial practice. Following is a brief description of each of these operations.
除了传统的钻，在工场实际中还包括别的类型的生产孔的方法。以下是对其中一些的简介。
Boring 镗孔
Boring involves enlarging a hole that has already been drilled. It is similar to internal turning and can, therefore, be performed on a lathe. There are also some specialized machine tools for carrying out boring operations. Those include the vertical boring machine, the jig boring machine, and the horizontal boring machine.
钻孔包括扩大已有的孔，类似于车削，因此可以在车床上操作。还有其他的特殊的机器可以用来钻孔。包括：立式镗床，坐标镗床和水平镗床。
counterboring扩孔
Already existing holes in the parts can be further machined
by counterboring as shown in Fig.24.3(a). In the counterboring operation, the hole is enlarged with a flat bottom to provide a space for the bolt head螺栓头 or a nut螺母, so it would be entirely below the surface of the part.
如图所示已经存在的孔还可以进行锪孔操作。在这次锪孔操作中，这个孔被放大出一个平底来留出螺栓头或者是螺母的空间，这样他们才能完全没入工件。
Countersinking
As shown in Fig.24.3(b), countersinking is done to enable accommodating适合 the conical seat of a flathead screw平头螺栓 so that the screw does not appear above the surface of the part.
如图所示，这个操作是为了给平头螺栓创造一个位置，这样他就不会出现在表面了。
Spot facing 锪孔
Spot facing operation removes only a very small portion of material around the existing hole to be provide a flat surface square to the hole axis, as shown in Fig.24.3(c). This has to be done only in case where existing surface is not smooth and is usually performed on casting or forgings.
锪孔只会从已存在的孔的表面切除少量的材料，使得孔的表面变得光滑，而且提高了同轴度，如图所示，这种操作往往是在工件表面不平整或者是锻铸出来的孔时用。
Reaming铰孔
Reaming is an operation used to make an existing hole dimensionally在尺寸上 more accurate than can be obtained by drilling alone. As a result of a reaming operation, a hole has a very smooth surface. The cutting tool used in this operation is known as the reamer.
铰孔是为了使已存在的孔在尺寸上可以比锪孔得到的更加的准确。铰孔得到的工件表面会变得非常的光滑，所用的刀具就叫做铰刀。
Tapping攻丝
Tapping is the process of cutting internal threads内螺纹. The tool is called a tap.
攻丝的过程就是制作内螺纹，刀具是叫丝锥。
Drilling operations can be carried out by using either electric hand drills or drilling machines. The latter differ in shape and size. Nevertheless the tools always rotates around its own axis while the workpiece is kept firmly fixed. This is contrary to相反 the drilling operation on a lathe, where the workpiece is held in约束 and rotates旋转 with the chuck卡盘. Following is a survey of the commonly used types of drilling machines.
钻孔工序既可以用手提电钻也可以用机器电钻。后者的不同是在于形状和尺寸。但是，当工件固定的时候，刀具总是绕着他自己的轴转动。（工件固定而刀具旋转）这与车床的工作原理相反。车床是把工件约束固定住，然后旋转卡盘。以下是一些常用的钻床的介绍。
Bench-type drilling machines are general-purpose, small machine tools that are usually placed on benches. This type of drilling machine includes an electric motor电动机 as the source来源 of motion, which is transmitted传送 via pulleys由。滑轮 and belts皮带 to the spindle, where the tool is mounted. The feed is manually手动的 generated进行 by lowering a lever handle手柄, which is designed to lower (or raise) the spindle.主轴
工作台型的钻床是多功能的，小型的工件一般会用这个加工。这种钻床是电动作为动能的来源，能量由滑轮，皮带传送到轴上工件安装的轴上。进给是通过控制专门设计的手柄达到的。
The workpiece is mounted on the machine table, although a special vise虎钳 is sometimes used to hold the workpiece. The maximum height of a workpiece to be machined is limited by the maximum gap间隙 between the spindle and the machine table
工件被固定在机床的平台上，有时用虎钳固定。允许加工的工件的最大高度是由刀具到钻床平台的距离决定的。
Upright Drilling Machines 立式钻床
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 base.
由于形状，立式钻床可以用于轻型的，中型的甚至是较大型的工
