Jewel Bearing
A low-friction synthetic ruby bearing used at high-wear pivot points within a watch movement.
Also known as: ruby bearing, jeweled bearing, jewelled bearing, hole jewel
Definition
A jewel bearing is the actual bearing formed by a synthetic ruby or sapphire in which a movement pivot runs. The jewel is drilled and polished to provide a hard, smooth contact surface with very low wear when correctly lubricated. Some high-load or precision locations pair a hole jewel with a cap jewel to control end-shake and retain lubricant. Jewel bearings are especially important in the fast-moving gear train and regulating organ, where metal-on-metal contact would create greater friction and wear.
Why it matters
Jewel bearings are a practical engineering feature, not decoration. Their condition, lubrication and alignment influence efficiency, wear and the long-term service life of a mechanical movement.