Component record · Escapement
Roller Table
VerifiedA disc mounted on the balance staff that carries the impulse jewel (and, on double-roller designs, a separate safety roller) for exchanging impulse with the pallet fork.
What it does
Transfers impulse from the pallet fork to the balance and back, and, in double-roller systems, provides the surface engaged by the fork's guard pin for safety against unlocking.
How it works
The roller table carries a projecting impulse jewel (roller jewel) that enters and leaves the pallet fork's slot once per balance oscillation, exchanging energy between the balance and the escapement.
In a single-roller escapement, one table carries both the impulse jewel and a crescent-shaped safety notch; in a double-roller escapement, a separate, smaller safety roller mounted lower on the staff carries the safety function, allowing a more robust impulse-jewel table.
The precise radial and angular relationship between the roller table's impulse jewel and the pallet fork's slot is critical to correct escapement action and is set during assembly and timing.
Evolution
Double-roller designs, separating impulse and safety functions onto two discs, became the standard refinement over the older single-roller table in high-grade lever escapements.
Known variations
- Single-roller table (impulse and safety combined)
- Double-roller system (separate impulse and safety rollers)
Identification for collectors
- Visible as a disc on the balance staff, within the pallet fork's horns, under a loupe or microscope
Common failure modes
- Chipped or loose impulse jewel
- Worn or chipped safety roller edge allowing the guard pin to catch and cause knocking
Related photographs
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
- Daniels, G., Watchmaking
Where sources disagree, the disagreement is stated rather than resolved silently.