一个切向键只能传递一个方向的转矩，传递双向转矩时，须用互成120°～130°角的两个键。用于载荷很大，对中要求不严的场合。由于键槽对轴削弱较大 ，常用于直径大于100mm的轴上。
A tangent key can only transfer the torque of one direction. When the two-way torque is passed, the two keys of 120 to 130 degrees are required. An occasion for he***y load and no strict requirement. As the keyway is greatly weakened to the axis, it is often used on a shaft with a diameter larger than 100mm.
销联接一般用来传递不大的载荷或作安全装置；另一作用是起***作用。常与带孔螺栓和六角开槽螺母配对使用，把销插入螺栓的孔与螺母的槽中，以防螺母松脱。销按形状分为圆柱销、圆锥销和异形销三类。
Pin connecti*** are generally used to transfer ***all loads or safety devices; the other is to play the role of . It is often paired with hole bolts and six angle slotting nuts to insert the pin into the hole of the bolt and the slot in the nut so as to prevent the loosening of the nut. The pin is divided into three types: cylindrical pin, conical pin and special pin.
机用虎钳结构缺点及使用中的隐患。机用虎钳有结构简单、夹紧力大、操作和维护方便等特点。但由于其必须具有广泛的适用性和操作的便捷性，其螺母与丝杆之间、活动座与虎钳体之间存在着较大的配合间隙，导致在装夹一些加工精度要求较高的产品时难以达到要求。
The structural shortcomings of the machine vise and the hidden danger in the use. The machine tool has the characteristics of simple structure, large clamping force, easy operation and maintenance. But because of its wide applicability and convenient operation, there is a large gap between the nut and the screw rod, the movable seat and the vice body, which results in the difficulty of meeting some requirements when clamping some products with high machining accuracy.