Hairspring

Definition

The fine spiral spring that returns the balance wheel to centre after each swing, and the part that decides how well a watch keeps time. A conventional hairspring is a steel alloy, which magnetism can disturb and temperature can soften. The modern answers are new materials. Rolex's Parachrom, a niobium-zirconium alloy, has been in its larger movements since 2000; its silicon Syloxi spring debuted in the 2236 in 2014. Omega's Si14 silicon spring has been in the 8500 family since 2011 and is the reason a Master Chronometer can be certified at 15,000 gauss. A Breguet overcoil, where the outer turn is raised over the spiral, is the traditional way to make the spring breathe concentrically, and appears in several of IWC's seven-day calibers.