Watch Terminology Dictionary

This refers to the mainspring. It is the power source that drives a mechanical watch and is generally housed in a barrel. Until the 1940s, mainsprings were mostly made of steel, but they were later replaced by Nivaflex, which is made primarily of cobalt, nickel, and chromium, is rust-resistant, and has greater elasticity than steel. This material allows the mainspring to be made thinner, which has become a major factor in extending the power reserve of mechanical watches.