THE BUSH

The bush jewel (or plain bearing) is typically made of beryllium bronze, brass, nickel silver, or even gold. Its shape resembles that of a jewel bearing (ruby). In watches, bushes are commonly used for components subjected to significant torque, such as the barrel or centre wheel. In clock repair, when a pivot hole in a plate becomes oval due to wear and lack of lubrication, it is usually re-bored to a larger diameter at the same centre point, and a bush is friction-fitted with a hole sized precisely for the pivot it must accommodate.

Useful link:
– Jewels, contra-pinions, and shock absorbers