hairspring

[ hair-spring ]

/ ˈhɛərˌsprɪŋ /

a fine, usually spiral, spring used for oscillating the balance of a timepiece.

Also called balance spring.

Origin of hairspring

First recorded in 1820–30; hair + spring

The gradual weakening or loss of elastic force of the hairspring is also a factor to be considered.

Rules and Practice for Adjusting Watches |Walter J. Kleinlein
The Curb Pins sometimes produce the ferric oxide mentioned by their action on the hairspring.

Friction, Lubrication and the Lubricants in Horology |William T. Lewis
The hairspring should be removed and the pivots known to be straight and polished before testing.

Rules and Practice for Adjusting Watches |Walter J. Kleinlein
When rust begins its attack upon any point of a hairspring there will be a constant loss in time until its advance is stopped.

Rules and Practice for Adjusting Watches |Walter J. Kleinlein

Thus the balance receives the power to keep it in motion, swinging it as far as the hairspring allows.

Time Telling through the Ages |Harry Chase Brearley

hairspring

/ (ˈhɛəˌsprɪŋ) /

horology a very fine spiral spring in some timepieces, which, in combination with the balance wheel, controls the timekeeping