Component record · Power
Stopwork (Geneva Stop-Work)
VerifiedA limiting mechanism, most often a Maltese-cross-and-finger arrangement, fitted to the barrel to restrict the usable number of mainspring turns.
What it does
Prevents the mainspring from being wound into its weakest and strongest extremes, keeping the watch running only over the portion of the spring's range that delivers the most even torque.
How it works
A five-pointed Maltese cross wheel is fixed to (or geared from) the barrel arbor; a single finger fixed to the barrel advances the cross by one point per revolution of the arbor.
The cross wheel is cut with one solid, unslotted point that physically blocks the finger once the spring has been wound to its limit, and stops rotation again at the fully run-down end, so only a restricted number of turns in the middle of the spring's range is ever used.
By confining running to the more linear part of the mainspring's torque curve, stopwork improves rate consistency, at the cost of sacrificing some of the spring's total stored energy and power reserve.
Evolution
A refinement retained mainly in high-grade watches and clocks, since going-barrel watches with detached lever escapements are less sensitive to torque variation and many everyday movements dispense with stopwork to maximise power reserve.
Known variations
- Maltese-cross (Geneva) stopwork, the most common form
- Simple pin-and-slot stopwork used in some clocks
- Stopwork omitted entirely in many ordinary going-barrel movements
Identification for collectors
- A small five-armed star wheel visible near the barrel on higher-grade movements is a Geneva stopwork
- Its absence does not indicate a fault — many watches are designed without it
Common failure modes
- Worn or chipped cross points causing the mechanism to bind or allow over-travel
- Loss of the finger spring pressure, letting the finger skip rather than index cleanly
Related photographs
No confidently matched photograph of this subject has been found yet. These photographs show a closely related record, and are not examples of the type described on this page.
Sources & references
- Daniels, G., Watchmaking
- de Carle, D., Watch and Clock Encyclopedia
Where sources disagree, the disagreement is stated rather than resolved silently.