POISING

Poising consists of uniformly distributing the Mass of a rotating part around its axis of rotation, in order to eliminate imbalances. In watchmaking, the poising of the Balance is a crucial step in Regulation / Adjustment: an unbalanced balance sees its center of mass move away from the axis, so that gravity assists or slows it depending on the watch’s position. This results in differences in rate between positions (horizontal and vertical), a major flaw for a Chronometer. Poising is carried out by removing material from the heavy side (drilling, Milling on the Felloe (rim base)) or by adjusting Balance Screws or timing weights. On modern smooth balances, Poising is achieved directly during machining and checked on dedicated machines. A perfectly poised Balance, combined with a well-centered Hairspring (balance spring) and a good Escapement, minimizes rate variations between positions and improves accuracy. Poising illustrates the importance, in chronometry, of the symmetry and regularity of the regulating organ. It is distinguished from rate regulation, which acts on the Frequency.