BEARINGS (commonly: stones or jewels)
The use of stones (synthetic Ruby / Jewels) in a movement generally aims to minimize friction between two components. The Bearings of a Movement (pivoting of the wheels in rotation) generate a lot of friction, responsible for a significant dissipation of energy. The use of synthetic Ruby / Jewel stones has therefore become widespread for all the Bearings of a watch. Depending on the wheel, its role, its dimensions and its Inertia, one of the three types of Bearings described in this chapter will be used.
SIMPLE BEARINGS
Most wheels of a Movement require simple Bearings. These have a single stone per pivot. The stone is pierced by a perfectly calibrated hole, into which the pivot is engaged. A circular recess, concentric with the stone’s bore, contains the Oil necessary for the Lubrication of the Bearing (Oil sink).
BEARINGS WITH ENDSTONES
Small-diameter pivots, which are not subjected to excessive torque, lend themselves to such Bearings. Endstone systems require two stones: the first is similar to a simple Bearing stone. A second stone (not pierced) limits the vertical Shake (play) of the wheel. Such a system involves conical pivots. Its advantage lies in the maximum reduction of friction (radial and vertical).
SHOCK-ABSORBERS
This system is mainly intended for the Bearings of Balance staffs and, more rarely, for those of the escapement wheel. The pivots of the Balance staff have a small diameter (to limit friction), while the Inertia of the Balance is high. The Endstone of a Shock-absorber is held to the Chaton (jewel setting) by a spring (the Lyre lug). In the event of a significant shock, the Endstone can move slightly, with the Lyre lug absorbing the shock and preventing the pivot from breaking.
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