Pallet fork

The pallet fork (German Anker) is the pivoting lever of the Swiss lever escapement. Two synthetic ruby pallets sit on its arms; they alternately catch the escape-wheel teeth, briefly halting the gear train, and then pass an energy impulse to the balance wheel. Without the pallet fork, the escapement would have no mechanism to convert the mainspring's energy flow into the regulated oscillation that drives a mechanical watch.

Function in the Swiss lever escapement

The pallet fork sits between escape wheel and balance and works alternately in two positions. In one position the entry pallet locks an escape-wheel tooth and the gear train stands still. When the balance swings past centre, its impulse jewel strikes the fork horn and tips it. The entry pallet releases the tooth, the tooth slides across the pallet's impulse face and delivers, through the fork, the impulse that sustains the balance's oscillation. The exit pallet then catches the next tooth — and the cycle begins again.

Each full balance oscillation corresponds to one tooth-step of the escape wheel. At 28,800 vibrations per hour that is eight steps per second — the source of the characteristic, slightly double-stroke ticking sound.

Materials and geometry

The fork itself is typically hardened steel; the pallets are synthetic ruby (aluminium oxide, Mohs 9). The geometry of the impulse faces is critical: the angle, length and polish of each pallet determine how efficiently energy is transferred. On modern premium calibres the pallets are ground to micrometre tolerances, cemented into the fork, then individually adjusted.

Wear and service

The pallet fork operates with sliding friction — escape-wheel teeth glide over the ruby impulse faces. That sliding contact is the central lubrication point in a mechanical movement. When the oil ages and thickens, balance amplitude drops and accuracy suffers. During regular service the pallets are cleaned, freshly oiled and inspected for cracks or chips. Visible damage means replacing the affected pallet or re-cementing it.

At our atelier in Munich we usually see pallet-fork problems as the symptom of an overdue service: amplitude below 220 degrees, high beat error, unstable rate in vertical positions. The escapement is always reviewed as a sub-assembly during service.

Co-axial as alternative

The co-axial escapement, invented by George Daniels and adopted by Omega in 1999, replaces the classical lever logic with radial impulse transfer and substantially less sliding contact. The pallet fork in that geometry carries three pallets and works against a two-tier escape wheel. The consequence is reduced lubrication dependency and a longer service interval — Omega rates its co-axial calibres for 8 to 10 years versus the classical lever's 4 to 6.