LEAF

In watchmaking, leaves are the teeth of pinions, traditionally made of Steel. Their number is generally between six and around twenty: this is why we speak of a pinion of six, eight, or ten leaves. Unlike the teeth of wheels, cut from Brass, the leaves of pinions are made of hardened and Polished steel, as they undergo significant stress and high speeds. In the Train (wheel train) of finishing, it is the teeth of the wheels (driving) that drive the leaves of the pinions (driven), transmitting energy from the Barrel to the Escapement. To improve the efficiency of these gears and reduce friction, the Leaves of the pinions are carefully profiled (involute or epicycloidal profile) and Polished: a well-finished pinion limits energy losses and wear. The number of Leaves, combined with the number of teeth on the wheels, determines the reduction ratios of the Train (wheel train). The Leaves illustrate the importance of tooth geometry and finishing for the precision and efficiency of the Movement.