Balance wheel, balance spring and other components and assemblies for a mechanical oscillator system and methods of manufacture

A method of forming a balance wheel assembly, the balance wheel assembly comprising:

• a thermally compensating non-magnetic balance wheel for use in conjunction with a thermally stable non-magnetic balance spring in a mechanical oscillator system in a horological or other precision instrument, the balance wheel including components of two different non-magnetic materials having different materials having different coefficients of thermal expansion, the components including a balance arm attached to a balance rim, the balance arm having a thermal expansion coefficient that is less than 6×10−6K−1 and the balance rim having a thermal expansion coefficient different from the thermal expansion coefficient of the balance arm, the components being arranged to give equipoise to the balance wheel and to cause a decrease in the moment of inertia of the balance wheel with an increase in temperature, wherein the decrease in the moment of inertia is arranged to compensate for changes in the elasticity of the balance spring caused by the increase in temperature;
• and
• a balance staff formed integrally with the balance wheel;
• the method comprising attaching the balance staff and balance wheel together when they are in their green state and using a bonding or heat treatment process to secure them together.