The quality of the clockwork in the prime mover has an important influence on the travel performance of the watch. It should have sufficient but not excessive output torque. The working principle of mechanical watch spring is that when the spring is gradually tightened, the swing of the balance wheel will inevitably increase with the increase of torque. When the spring is fully tightened and reaches the maximum working torque, the watch will move. If the swing of the balance wheel still cannot reach the required swing, it is necessary to consider whether the output torque of the spring is enough. Excessive output torque will produce "bump" phenomenon. When the spring fluctuates greatly at any time, the time of one swing of the speed regulating mechanism will also change, and the watch will go faster and slower, which is related to the uneven output torque of the spring.

The spring part has been treated with PTFE film, and there is no need to add lubricant, which can avoid pollution to the movement without box cover in the original mechanism. At present, the watch spring has adopted a sheet-like outer hook, which can move flexibly in the radial direction, so that all coils are almost concentric when the spring is tightened and loosened, and the friction between coils is reduced. In an automatic watch, the automatic winding device will continue to work after the spring is completely wound. In order to prevent the spring from overloading and breaking or damaging other parts of the automatic mechanism, the outer end of the spring of the automatic watch is equipped with a long auxiliary spring similar to a hook. The former and the latter are fixed on the spring by spot welding, and the winding mode should be clockwise.