How do mechanical watches work?
The energy for driving mechanical movements comes from the winding stem. It is wound on hand-wound watches by turning the crown and, in the case of automatic watches, over a ball-bearing rotor. The motion of the watch when moving the arm cause the rotor to pivot on its staff thereby winding an s-shaped mainspring. In automatic movements, this spring is typically wound in both directions of rotation. A slipping clutch prevents over-tightening of the mainspring. The spring stores the energy and is housed in the mainspring barrel. When the spring relaxes over time, the barrel is turned, which causes all other wheels in the gear train to turn.
The escapement allows the watch’s uncontrolled course of the gear train to advance or “escape” by a fixed amount, converting the transmitted rotational energy into a periodic cycle. This cycle is regulated by the balance wheel. Finally, the movement of the gear train is transmitted to the hands and so the time is displayed on the dial.
Care, revision and cleaning of a mechanical watch
Most high-quality mechanical movements use synthetic gems like rubies as bearing for moving parts. There is less friction between stone and steel than between two steel components, which reduces wear and increases accuracy. However, friction can never be completely avoided and even the finest dirt particles that have penetrated the watch can contribute to the wear and tear of lubricants and materials. Extreme temperatures can accelerate this wear as well and should therefore be avoided, just like magnetic fields, that can damage the many fine, moving parts.
There is no fixed revision interval, since it depends very much on personal wearing behavior and, of course, on the movement itself, how often a revision is due. As a rule of thumb, you can say that a mechanical watch has to be revised every 3 to 7 years – here the watchmaker disassembles and cleans the complete movement before it is reassembled and oiled.