A watch’s main timekeeping mechanism is called its movement. Today’s watch movements fall into two categories: Automatic mechanical or quartz. Automatic mechanical movements mark the passage of time by a series of gear mechanisms. Most automatic movements are wound by the normal, everyday movement of your wrist, which charges the watch’s winding reserve. Quartz movements are powered by a battery and do not stop working once removed from your wrist.
The regulating organ of a watch with a mechanical movement that vibrates on a spiral hairspring is called the balance wheel. Lengthening or shortening the balance spring makes the balance wheel go faster or slower to advance or retard the watch. The travel of the balance wheel from one extreme to the other and back again is called oscillation.
This series of small gears in both quartz and mechanical movement watches is responsible for transmitting the power from the battery (in a quartz watch) or spring (in a mechanical watch) to the escapement, which distributes the impulses that mark the time.
EscapementThis part of the watch restricts the electrical or mechanical impulses of the gear train, metering out the passage of time into equal, regular parts.
The motion work is a series of parts inside a watch that receive power from the escapement and gear train, which distribute and generate the watch’s power. The motion work is responsible for actually turning the watch’s hands.
The mainspring is the energy source responsible for powering the watch movement (as opposed to a battery in a watch with a quartz crystal movement). The spring is wound, either manually (using the winding stem) or automatically, by the motion of the wearer’s wrist. Potential energy is stored in the coiled spring, then released to the gear train which transmits the power to the escapement and motion work, which turns the hands on the watch dial.