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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, brass 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. (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)。
