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.
型面联接：是利用非圆剖面的轴与相应形状的零件的毂孔配合而构成的联接，作为机械传动中的联接方式，型面联接相对于传统的键联接相比，具有联接强度高，没有应力集中，可以传递大扭矩且效率高的同时也可以承受冲击载荷，并且对于一些大型机械装备来讲其拆装方便及维修便利。
is the hub hole type surface connection: the non-circular section axis and the corresponding shape parts with a connection, as the connection mode in mechanical tran***ission, compared with the traditional linkage type surface connection compared with connecting strength, no stress , can large torque and high efficiency at the same time it can withstand the impact load, and for some large mechanical equipment for its disassembly and convenient maintenance.
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.