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The Encyclopedia of Horology

Component record · Dial & hands

Cannon Pinion

Verified

A friction-fitted pinion mounted on the centre wheel arbor that carries the minute hand.

What it does

Transfers rotation from the centre wheel arbor to the motion works and minute hand, while allowing the hand to be independently set without disturbing the going train.

How it works

The cannon pinion grips the centre wheel arbor by friction (a spring collet or split, slightly tensioned bore) rather than being rigidly fixed, so the hands can be turned to set the time without forcing the going train to turn with them.

Its pinion leaves mesh with the minute wheel, which in turn drives the hour wheel through the motion works reduction, so the cannon pinion is the first stage translating one-revolution-per-hour centre wheel motion into hour and minute hand display.

Excessive wear or insufficient friction in the cannon pinion's grip on the arbor causes the minute hand to slip during running, a common minor fault distinct from train problems.

Evolution

The friction-drive principle has remained essentially unchanged since separate hand-setting motion works were introduced, though modern cannon pinions are made to tighter tolerances for consistent grip.

Known variations

  • Cannon pinion with built-in friction spring
  • Cannon pinion with separate friction washer
  • Indirectly driven cannon pinion: where the centre of the movement is used for other work, the cannon pinion is driven from the train through additional wheels rather than sitting on the centre-wheel arbor

Identification for collectors

  • A minute hand that can be pushed around by finger pressure without visible damage, yet slips during running, points to a worn cannon pinion

Common failure modes

  • Loss of friction grip causing the minute hand to slip or lag
  • Wear at the pinion leaves

Photographs

Detached cannon pinion from a Seiko Bell-Matic 4006A workshop record — hollow shaft and pinion teeth; source captions this repair stage as cannon pinion tightened
Detached cannon pinion from a Seiko Bell-Matic 4006A workshop record — hollow shaft and pinion teeth; source captions this repair stage as cannon pinion tightened — Watch Guy workshop photo library; individual photographer not separately stated, Copyright workshop photograph — rights pending; permission not established; reduced-size JPEG copy. Watch Guy — photo P1360915, cannon-pinion repair record

Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.

Sources & references

  1. de Carle, D., Practical Watch Repairing
  2. Daniels, G., Watchmaking

Where sources disagree, the disagreement is stated rather than resolved silently.