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MAINSPRING WINDERS

What is a mainspring winder?

The mainspring winder is a hand tool designed to wind, in a controlled manner, a flat spring of considerable length. Its most emblematic use in watchmaking concerns the Mainspring, the installation of which cannot be carried out without suitable tools, owing both to the considerable length of the blade and to the energy it releases when it suddenly unwinds.

In its most common architecture, the Mainspring winder consists of a hollow cylindrical body — often made of Brass — fitted at its center with a rotating spindle onto which the inner end of the spring is hooked. A crank, sometimes replaced by a removable Key, drives the rotation of the spindle. A circular guide — or a Set of interchangeable cylinders of different diameters — compresses the coils as the winding progresses, allowing the Blade to be precisely gauged once the winding is complete.

The central use of the Mainspring winder today relates exclusively to servicing older pieces or restoration work. It involves inserting a relaxed spring into the Barrel drum while respecting the winding direction and avoiding any twisting of the Blade. The spring, previously wound in an intermediate cylinder of the Mainspring winder whose diameter matches that of the drum, is transferred by simple pushing into the latter, which receives the coils without deforming them. At the end of the transfer, the Barrel arbor is put in place and the cover Barrel closes the assembly.

Beyond this emblematic use, devices related to the Mainspring winder are involved in the manufacture of Hairsprings (balance springs). Before the Heat treatments which will durably fix their geometry and elastic properties, the metal wire, previously drawn to the desired dimensions, is wound into a spiral around a mandrel with a precise pitch. This cold winding, carried out with tooling based on the Mainspring winder principle, gives the future Hairspring (balance spring) its primary shape, which will then be stabilized by annealing.

Useful links:

– The Barrel

– The Hairspring (balance spring)