Component record · Plates & finishing
Bearings / Bushings
VerifiedThe plain (non-jewelled) holes or inserted bushes in plates and bridges through which train and other arbors pivot.
What it does
Support rotating arbors with minimal play and friction at points not warranting a jewel.
How it works
In economical or older movements many pivots run directly in holes bored in the brass plate itself. Repeated use gradually elongates and wears these holes, allowing excess pivot play (shake) that can cause a wheel to run out of correct depth with its neighbours.
A common repair, especially in clockwork, is to close and re-bore a worn hole, or to press in a separate hard bushing (sometimes called a bush) to restore a true, close-fitting bearing surface without replacing the whole plate.
Evolution
Higher-grade watchmaking increasingly jewelled these positions, but plain brass bearings remain standard away from the fast-moving balance and escapement in most movements, and are near-universal in clock movements.
Known variations
- Plain drilled bearing in the plate
- Inserted brass bushing
- Jewelled bearing (see Jewels) at higher-wear points
Identification for collectors
- Excess sideways or up-and-down play in a wheel's pivot indicates a worn bearing needing bushing
Common failure modes
- Wear enlarging the hole, causing mis-depthing and rough running
- Scoring from lack of lubrication
Related photographs
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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
- de Carle, D., Practical Watch Repairing
Where sources disagree, the disagreement is stated rather than resolved silently.