Axles are categorized into cross shafts, housing shafts, universal joints, pin shafts, shafts, star shafts, and elastic couplings, etc. They are primarily used in various aspects of machine tools.

A shaft coupling is a commonly used component in mechanical products, designed to connect two shafts or a shaft to a rotating part. It rotates together with the shafts without disengaging, without altering the rotation direction, and without changing the torque magnitude during the transmission of motion and power. Some couplings also feature functions to compensate for relative shaft displacement and to dampen vibrations. Moreover, certain shaft couplings can serve as safety devices to prevent overloading of the drive shaft system.