In the transmission device of machine tool, the commonly used transmission parts include pulley, gear, worm turbine, gear rack and screw nut, etc. Through these transmission parts, the power source and the actuator, or the two actuators are connected, which is called the transmission connection. A series of sequentially arranged transmission parts that constitute a transmission link are called transmission chains.

The chain is generally a metal link or ring, which is mostly used for mechanical transmission and traction. Chains used to block the passage of traffic (such as in the street, at the entrance of a river or harbor), and chains used for mechanical transmission.