Mechanical clock gears

Mechanical clock gears combine millimeter precision and goldsmith artistry in centuries-old movements.

About this subject

The gears of a mechanical clock form the heart of the movement, transmitting power from the mainspring to the escapement. Each component is machined within tolerances of less than 0.01 mm, ensuring that stored energy is released at regular intervals. In classical watchmaking, cogwheels were handcrafted from brass or steel, often decorated with engravings such as perlage or Geneva stripes, techniques that both embellish and reduce surface friction.

Tooth profiles follow precise mathematical principles, such as the involute curve, which guarantees smooth and constant contact between gears. In medieval tower clocks, like that of Salisbury Cathedral (1386), iron wheels were forged with straight teeth, while 18th-century clocks already used cycloidal profiles for greater efficiency. Christiaan Huygens' invention of the pendulum in 1656 demanded finer and more accurate gears, leading to the anchor escapement and later the lever escapement.

Beyond mechanical function, gears bear witness to technological evolution: the first portable watches, such as Peter Henlein's "Nuremberg egg" (ca. 1505), used steel springs and bronze wheels, materials that remain standard in Swiss haute horlogerie movements today. Their durability is such that many 19th-century clocks still work, like the pendulum clock by Gustave Serrurier-Bovy displayed at the Musée d'Orsay, whose original gears remain operational.

Frequently Asked Questions

How do mechanical clock gears work?

Gears transmit power from the mainspring to the escapement, reducing speed through specific gear ratios. Each pair of cogwheels converts continuous motion into regular pulses controlled by the escapement.

What is the difference between brass and steel gears in watchmaking?

Brass (an alloy of copper and zinc) is softer and corrosion-resistant, used for train wheels and dials. Steel, being harder, is used for shafts and high-friction parts like the escapement pinion due to its wear resistance.

Why do gear teeth have specific shapes?

Tooth profiles (involute or cycloidal) ensure continuous and smooth contact, minimizing friction and noise. Poorly designed teeth would cause vibrations and time inaccuracy, compromising the watch's chronometry.