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.

螺旋副的间隙大，旋转时费力，使用中稳定性差。机用虎钳开合行程大，螺旋副的运行长度较长，为保证能够快速装夹，（金属加工真不错）机用虎钳螺旋副的螺距较大。较大的螺距意味着较大的螺旋升角，转动单圈进给量较大，使用时较费力；较大的螺距需要更大的配合间隙来确保螺旋副的正常使用。

The clearance of the helix pair is large, the rotation is hard and the stability of the use is poor. The machine has large opening and closing stroke, and the operation length of the screw pair is longer. In order to ensure quick clamping, metal machining is good. Larger pitch means larger spiral angle, larger single turn feed and more laborious use. Larger pitch needs more fit clearance to ensure the normal use of screw pair.