Producing small precision components from metal bar stock on an automatic lathe, using turning and related machining operations.
Décolletage is bar turning: a rotating metal bar is fed through an automatic lathe, the décolleteuse, and cut by one or, usually, several tools, with the tool movements, rotation speed and bar feed all automated. In watchmaking, it produces parts of revolution such as screws, pins, arbors, pinions and barrels, from a few tenths of a millimeter to about 20 mm in overall diameter. Horopedia states that these machines can turn pivots of 0.08 mm with a precision on the order of a micrometer.
The machines may use mechanical cams or computer numerical control (CNC). Cam-driven lathes were widely used until the 1980s and remain in use in some workshops; CNC machines are more precise, productive and versatile. In Switzerland, décolletage is one of three specializations of the four-year micromechanic CFC (micromécanicien), chosen from the second year, and the training includes calculating a set of cams.
In job listings
The term appears in component manufacturing roles: décolleteurs, micromechanics and CNC machinists who set up and run automatic lathes, and apprentices training in bar turning. It signals machine work upstream of the watchmaker’s bench, making the small parts that movement assembly later puts together. See current micromechanic roles.
