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The Encyclopedia of Horology

Component record · Power

Rotor Bearing

Partially verified

The bearing on which an automatic winding rotor turns.

What it does

Supports the rotor so it swings freely with minimal friction.

How it works

A ball race or jewelled pivot carries the rotor's weight and side loads from wrist motion.

Wear here produces rotor wobble and, eventually, contact with the case back.

Evolution

Ball bearings became common as an alternative to jewelled centre pivots.

Known variations

  • Jewelled rotor pivot
  • Ball-bearing rotor

Identification for collectors

  • A scraping sound as the watch is moved usually means rotor bearing wear.

Common failure modes

  • Bearing wear allowing rotor contact
  • Contaminated race

Diagram

crownsliding clutchsetting wheelswinding pinion and ratchet
Schematic: keyless winding and hand setting. An outline schematic drawn to show the arrangement of the parts discussed here. It is not a dimensioned working drawing and does not depict a particular maker's calibre.

Sources & references

  1. de Carle, D., Practical Watch Repairing
  2. de Carle, D., Watch and Clock Encyclopedia
  3. Daniels, G., Watchmaking

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