Coupling is a mechanical part used to connect two shafts (driving shaft and driven shaft) in different mechanisms so that they can rotate together to transmit torque.In high-speed and heavy-load power transmission, some couplings also have the function of buffering, damping and improving the dynamic performance of the shafting.The coupling is composed of two halves, which are respectively connected with the driving shaft and the driven shaft.The general power machine is mostly connected with the working machine by means of a coupling.There are three types of coupling shaft deviation, one type: radial deviation, that is, the two shafts are parallel but the lines are no longer on the same straight line. The deviation generated at this time is called radial deviation; two types are angular deviations, that is, two shafts The deviation caused by forming an angle with each other; 3 types are the axial deviation, that is, the deviation caused by the reciprocating micro-motion of the two shafts.

　　Deviation not only occurs in the assembly of equipment, but also factors such as vibration, thermal expansion, bearing wear and so on in the working process will cause deviation. Therefore, it is recommended to adjust the axial deviation to less than 1/3 of the maximum value.The allowable value of large deviations for various types of couplings means that when there is only one type of deviation, when two or more types of deviations exist at the same time, the allowable value should be less than 1/2 of the large deviation in each specification table.