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The Encyclopedia of Horology

Glossary · Mechanism

Pallet fork

The lever that carries the pallets and transmits impulse between the escape wheel and the balance in a lever escapement.

Explanation

In a Swiss lever escapement the pallet fork carries two pallet stones — entry and exit — that alternately lock and receive impulse from the escape wheel. The fork's notch engages the balance's impulse pin, so the fork both gives impulse to the balance and is unlocked by it. The fork, its staff and the guard pin form a precise, easily damaged assembly.

Geometry terms used in documentation include lock, draw, drop and lift. Draw pulls the fork against its banking to keep the train locked; drop is the small free motion as a tooth leaves a pallet. These are measured during escapement adjustment with the movement stripped to the escapement; they cannot be judged from an assembled watch's sound alone, and no safe owner-level adjustment exists.

Record pallet-stone condition, staff pivots and any documented adjustment only from service notes. A fork that has been bent, re-stoned or polished changes the escapement's behaviour and is a significant condition fact.

Sources & references

  1. de Carle, D., Practical Watch Repairing — technical further reading; exact procedures require calibre documentation
  2. Reymondin et al., The Theory of Horology — construction and terminology further reading

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

Distinctions at a glance

ElementFunctionLimit
Entry palletLocks and receives impulse first in sequenceNot interchangeable with the exit stone
Exit palletCompletes the alternate locking cycleNot a duplicate of the entry stone
Guard pinKeeps the fork positioned against bankingNot an impulse element
Fork slot and impulse pinTransmit impulse to the balanceNot an owner adjustment point

What to record

  • Distinguish entry and exit pallet observations.
  • Keep fork condition separate from balance and hairspring condition.
  • Cite service documentation for any escapement adjustment claim.

Do not attempt to move banking pins or pallet stones; escapement adjustment requires the train removed and specialist measurement.

In the object catalogue

Catalogued objects whose own source record mentions “Pallet fork”. The quoted line shows where; it is the seller’s or museum’s wording, not independent verification.