Bevel gear

In watchmaking, the bevel gear is not an aesthetic detail: it is the technical solution that allows me to transmit torque between non-parallel axes. The profile of the teeth converges toward a common vertex, exactly like the geometric cone from which it takes its name. Without this geometry, any inclined dial, any sphere rotating on multiple axes, any three-dimensional complication would be impossible to actuate with precision.

The most widespread application over the last twenty years concerns inclined dials. In the MB&F Legacy Machine FlyingT, the movement is constructed vertically, and the hours/minutes dial is positioned at 50 degrees, facing the wearer. Bevel gears transmit torque between the internal planes and the dial plane: without them, the case could be conceived, but not built. The same principle applies to the LMX, where the dual inclination—vertical and lateral—of the two dials requires a more articulated kinematic chain.

A special case is the Hautlence Sphere Series 3. Here, four bevel gears arranged on axes intersecting at 21-degree angles control the rotation of a jumping sphere on three simultaneous axes. The visual result seems chaotic; the underlying mechanics are instead rigidly deterministic. The sphere presents the next hour with a rotation that appears random but is perfectly calculated.

Then there is the variant of the conical tourbillon, developed by Éric Coudray for HYT and inspired by a patent by Walter Prendel from 1928. In this architecture, the balance spring is inclined at 30 degrees to the horizontal, the escape wheel at 15 degrees, the pallet at 23 degrees. The tourbillon completes one rotation every 30 seconds. The objective is to compensate for the effect of gravity on multiple planes, not just the vertical one.

A separate category is the conical jewel. In the Greubel Forsey Hand Made 2, a large conical synthetic ruby, worked entirely by hand over approximately four months, rotates and rises when the watch is wound, mechanically actuating the power reserve indicator. It is not decoration: it is a functional component whose conical shape is an integral part of the kinematics. The same logic applies to the dual-barrel conical power reserve mechanism: the conical geometry compacts more information in less space compared to a conventional hand.

On my bench, I have seen many disassembled movements that use bevel gears in almost invisible positions, far from the display. It is one of those components that the end customer never sees, but that the watchmaker recognizes immediately upon opening the case.