Couplings are also called shaftacoplamientos. A mechanical component used to firmly connect the driving shaft and the driven shaft in different mechanisms to rotate together and transmit motion and torque. Sometimes it is also used to connect shafts with other parts (such as gear, belt pulley, etc). It is often composed of two halves, which are connected by keys or tight fits, respectively, and fastened to the ends of the two shafts, and then the two halves are connected in some way. The coupling can also compensate for the deviation (including axial, radial, angular, or integrated deviation) between the two shafts due to inaccurate manufacturing and installation, deformation or thermal expansion during work, as well as alleviate impact and absorb vibration.
Most of the commonly used couplings are standardized. Under normal circumstances, it is only necessary to correctly select the type and size of the coupling, calculate the load capacity, check the rotation angle（axis break angle). when the rotation speed is high, the dynamic balance check is required, etc.