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The Encyclopedia of Horology

Glossary · Mechanism

Lever notch

The slot in a lever escapement's fork that engages the roller's impulse pin.

Explanation

The lever notch is the slot at the end of the pallet fork that the balance's impulse pin enters to give and receive impulse. Its width and the depth the pin enters are critical: too shallow and the pin can jump out, too deep and power is wasted. Wear in the notch shows as a bright step and affects escapement action.