Skip to content
The Encyclopedia of Horology

Glossary · Regulation

Breguet overcoil

A hairspring whose outer turn is raised and curved over the body of the spring.

Explanation

The raised terminal curve lets the spring 'breathe' concentrically, which improves isochronism and positional rates. Overcoils are fragile and their forming is a specialist skill; a flattened or mishandled overcoil is a common cause of poor rates in older fine watches.