Glossary · Mechanism
Cannon pinion
A motion-work pinion commonly carrying the minute hand, with a friction coupling that permits hand setting.
Explanation
In a conventional arrangement, the hollow cannon pinion fits on the centre-wheel arbor and carries the minute hand. Its teeth drive the minute wheel, which in turn drives the hour wheel. The friction coupling allows indication to be set without forcing the entire going train backwards. This describes a common layout, not every indirect-drive or off-centre display mechanism.
The coupling must transmit normal running torque while allowing controlled slip during setting. Insufficient friction can let the movement run while the hands lag; excessive friction can make setting difficult. Those symptoms are not exclusive diagnoses: hand contact, motion-work wear or other faults can also affect indication. The archive's detached Seiko Bell-Matic cannon-pinion photograph shows the hollow part and teeth in a workshop context; it does not demonstrate the fit in a different calibre.
Sources & references
- de Carle, D., Practical Watch Repairing — technical further reading; exact procedures require calibre documentation
- Reymondin et al., The Theory of Horology — construction and terminology further reading
Where sources disagree, the disagreement is stated rather than resolved silently.
What to record
- Identify the exact motion-work layout.
- Keep indication faults separate from oscillator rate.
- Caption a detached part with its original calibre and source.
Tightening a cannon pinion requires controlled specialist work; squeezing it with pliers can damage the part.