A spiral spring that provides power to a mechanical movement. After being wound either manually or by an automatic winding system, the mainspring, which is housed in a barrel affixed to a toothed disk, gradually uncoils. As it does so, it causes the barrel to rotate slowly on its arbor, keeping the watch’s gear train in motion. Most watch mainsprings are made of Nivaflex, an alloy that is elastic and relatively resistant to breakage.
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