hairspring

[hair-spring]

noun Horology.

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

Origin of hairspring

First recorded in 1820–30; hair + spring

Also called balance spring.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for hairspring

Historical Examples of hairspring

If this is a balance pivot, be very careful to see that your balance is true and poised before putting on hairspring and roller.
Scientific American Supplement, No. 664, September 22,1888
Various
Presume the existence of a vertical line through the center of hairspring and collet as shown at "A B" Fig. 9.
Rules and Practice for Adjusting Watches
Walter J. Kleinlein
Hairspring concave or convex in form instead of perfectly level.8.
Rules and Practice for Adjusting Watches
Walter J. Kleinlein
The complete balance and spring can be inserted and the pivots can be refinished without disturbing the roller or hairspring.
Rules and Practice for Adjusting Watches
Walter J. Kleinlein
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

British Dictionary definitions for hairspring

hairspring

noun

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

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012