How to find the right Jewel Bearings AI guide
Written by an AI model from its trained knowledge.
What the AI looks for in Jewel Bearings
- Jewel type
- Match the type: hole jewel (olive or flat), cap/end stone, cup jewel, V-jewel or pallet stone. Each type supports a different pivot geometry, so they are not interchangeable.
- Hole diameter
- Hole must fit the measured pivot diameter with proper side shake, measured in hundredths of a millimetre for watch work. Too tight binds the pivot. Too loose lets it wobble and affects timekeeping or instrument accuracy.
- Outside diameter and height
- OD must suit a friction-fit press into the plate or setting, and height must sit at the correct endshake. A wrong OD either won't hold or cracks the plate. A wrong height changes endshake.
- Material
- Synthetic ruby or sapphire (corundum) is the standard. Glass or plastic 'jewels' are not equivalent. Corundum's hardness and low friction against steel pivots is the whole reason to use a jewel.
Brands that matter
- Seitz: Swiss jewelling system and assortments widely used by watchmakers.
- Swiss Jewel Company: Industrial jewel bearings, orifices and sapphire components.
- Bird Precision: Jewel bearings, V-jewels and ruby or sapphire components for instruments.
What to avoid
- Unspecified 'jewel' assortments with no hole and OD sizes listed.
- Pressing jewels without a proper jewelling tool, which risks cracking stone or plate.
- Lubricating cap jewels with general-purpose oil instead of a watch or instrument oil.
Questions
How do I find the right replacement watch jewel?
Measure the pivot diameter and the plate hole or old jewel OD, then choose by hole, OD and height. The movement calibre's parts data gives the exact sizes when available.