Automatic winding

How does automatic winding work?

Automatic winding, also called self-winding, uses movement to wind the mainspring of a mechanical wristwatch. A moving weight, usually called a rotor, transfers motion to the winding system. Energy is stored in the spring; this does not guarantee uninterrupted running.

Use and power reserve

An automatic watch can stop when left without sufficient winding. Its running time depends on the movement and the amount of stored energy, among other factors. A stated maximum power reserve does not mean that briefly wearing the watch will fully charge the spring.

Whether and how a particular automatic watch can be wound through its crown must be established from the instructions for the correct calibre. Do not apply one number of crown turns or one procedure to every watch. Tissot gives specific differences between its movements and warns against vigorous shaking and forcing the mechanism.

Assessing a pre-owned watch

Request documentation of its calibre, function, service history and measured power reserve. Record how the watch was wound before measurement. A watch that runs after being moved has not thereby been checked for accuracy, winding efficiency or wear.

See also manual winding, power reserve and our wristwatches.

Sources

Longines: automatic and quartz movements and movement types. Tissot: winding instructions.