How a mechanical watch movement works

A mechanical watch movement is at its core a small machine that converts the energy you supply by hand into a steady predictable movement of second minute and hour hands. There is no battery and no circuit — only springs gears and a finely tuned mechanism working together to fractions of a millimetre. Understanding this structure is the foundation for all repair work because you can only find a fault once you know how the watch should behave when functioning correctly.

§Energy source: the mainspring

The watch's energy comes from the mainspring also called the main spring—a flat metal strip coiled tightly in a spiral inside a spring barrel. When you turn the crown the spring is wound up and the energy you put into it is released gradually over hours or days. The more tightly wound the spring the more power the watch mechanism has available but also the more the rest of the mechanism must be able to regulate so the power does not just rush through at once.

§The gears carry the power on

• 01The center wheel receives the force from the mainspring and usually drives the minute hand
• 02The idler wheel (third wheel) carries the force through the mechanism
• 03The pinion (fourth wheel) typically drives the second hand
• 04The escapement wheel is the last link before the force reaches the escapement itself

§The escapement — the heart of the watch

Without an escapement the spring would just unwind all its energy in one moment. The escapement—in most modern watches an anchor escapement—is the mechanism that releases the energy in small, precisely measured pulses. Each pulse corresponds to the tick you can hear if you hold a mechanical watch close to your ear. The escapement is at the same time the part of the watch mechanism most subject to wear because it works constantly and at high speed, and therefore requires special care when cleaning and lubricating.

§Balance Wheel and Spiral Spring Control the Beat

The Balance Wheel is a Small, Weighted Wheel that Swings Back and Forth on Its Own Axis. The Swings are Controlled by a Very Thin Spiral Spring, Which Pulls the Wheel Back to Its Starting Point After Each Swing. Together the Balance Wheel and Spiral Spring Function as the Watch's Metronome — It is This Oscillation Frequency that Determines How Many Times Per Hour the Escapement Releases Energy. Most Modern Calibres Oscillate Several Times Per Second, While Older or Certain Speciality Calibres May be Lower; the Watch Maker's Timing Equipment Uses Precisely This Frequency to Show Whether the Watch Runs Accurately.

§Automatic Tensioning

In an automatic (self-winding) watch, there is also a rotor — a half-moon-shaped weight that swings freely when the watch is moved with the wrist. The rotor's movement is transmitted through a small gear system to tension the mainspring, so the watch in practice keeps itself wound as long as it is worn regularly. The crown can usually still be used to wind the watch manually if it has been standing still for a long time.

When you know this chain of cause and effect — from hairspring to gear train restraint and balance — troubleshooting becomes far more systematic. A watch that runs too fast too slow or not at all points almost always to a specific place in this chain and that's where your professional understanding truly makes a difference for the customer.