MINUTE WHEEL
The minute wheel is a mobile composed of a solid brass wheel plate riveted to a steel pinion. The assembly’s axis is pierced and pivots on a post driven from the dial side of the mainplate, located near the minute hand pivot point (usually at the centre). The role of the minute wheel is to multiply, through its gear ratio, the rotation speed of the cannon pinion (which carries the minute hand and drives the minute wheel) so that the pinion of the minute wheel drives the hour wheel (stacked on top of the cannon pinion and carrying the hour hand) twelve times more slowly. A thin minute bridge generally holds the minute wheel and the gears, limiting the vertical movement of the pinion.
The appearance of the minute wheel is intrinsically linked to that of the minute hand from which it derives. The first minute hands date back to the end of the 16th century. However, it did not take long for the minute wheel to exist and fulfil its primary role. The fundamental role of the minute wheel is to multiply the rotation speed of the minute hand compared to that of the hour hand. Due to the simplicity of the solution, the minute wheel has not undergone significant evolution since its inception.
The minute wheel consists of a solid brass wheel plate and a steel pinion. Both components of this mobile can be crafted on a lathe. Their tooth profiles can also be cut using a milling cutter and s dividing tool on the lathe. A shoulder turned at the base of the pinion allows the wheel plate to be riveted to it, once the two components are finished.
Depending on the production volumes involved, the method described here can also be applied on a semi-artisanal level (with small batches), as well as on an industrial level (in fashion and high production volumes). The automatic lathe is the most suitable machining solution for producing the wheel plate and the minute wheel pinion (including tooth cutting). Both components will then be decorated by hand or industrially, depending on the desired finishes, before the wheel plate is riveted to its pinion. Producing the wheel plate by stamping would not offer significant advantages, as the tooth cutting would then require a subsequent operation on a gear-cutting machine.