BUSH

The bush is a bearing auxiliary of cylindrical shape, screwed or pressed into the main plate or a bridge, which receives the end of a pivot. Its shape resembles that of a watchmaking jewel, but the bush is generally made of bronze-beryllium, in brass, in German silver or, more rarely, in gold. Its role is twofold: on one hand, it ensures a precise bearing surface for the pivot while facilitating the lubrication localized; on the other hand, it allows the individual replacement of a worn bearing without having to replace the entire main plate. Bushes are particularly common in large-sized movements, such as longcase clocks or marine chronometers, where the load on the pivots is significant. Some bushes have a groove or a flat that allows them to be screwed or unscrewed using a suitable tool during maintenance operations. In wristwatches, they are rarer, the Ruby / Jewel synthetic stone generally fulfilling this function.