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Watch Word this Week: Frequency

How the speed of a watch movement can affect its workings.

If your mechanical watch has a see-through caseback, you’ll have noticed that one component is in perpetual motion: That’s the balance wheel – the beating heart of the watch movement – moving back and forth in order to keep time. Each time the balance wheel swings in one direction, that’s one vibration, or a half-oscillation.

Silicon mobile escapement parts (the parts in blue), as seen in the high-frequency movement of Breguet’s Classique Chronometrie 7727, are lighter and need virtually no lubrication.

Most watch movements run at 28,800 vibrations per hour (vph) or 4Hertz (Hz), though 21,600 vph is also common. (The frequency in Hz is the number of oscillations per second.) High-frequency movements are those that run at 36,000 vph or higher, which promise better timekeeping as the balance wheel has more inertia, and is hence more stable even with external shocks. But increased frequency also means more wear and tear, which is why high-frequency movements only started to proliferate in the last decade, when advances in materials alleviated the problem.

The Breguet Classique Chronometrie Ref. 7727 runs at 10 Hz, or 72,000 vph, more than twice the frequency of a normal movement. That’s thanks to magnetic pivots on the balance wheel that almost eliminate friction entirely, as well as silicon escapement parts. In this case, the race is indeed to the swift.

Breguet’s Classique Chronometrie 7727, available in rose or white gold, took the “Aiguille d’Or” top prize at the Grand Prix de l’Horlogerie in 2014.