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THE COLLET

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Figure 1

Exploded view of the regulating organ

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Figure 2

Diagram of a collet

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1. General description

Generally speaking, the collet refers to a split washer that can pivot more or less freely around the Axis on which it is fitted. For example, collets can be found on the felloe of some Balances with variable inertia.

In all mechanical Movements, the collet is the connecting element between the Hairspring (balance spring) and the Balance staff. It is one of the components of the Regulating organ and it plays an essential role in Regulation / Adjustment operations.

This is a split washer made of Brass including an eccentric transverse hole intended to receive the hairspring hook. When the hairspring hook is correctly formed, it is engaged in the transverse hole of the collet. Once properly positioned, it is pinned there with a brass pin (Figure 3).

Figure 3

Traditional collet

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Greiner colleting is particularly well suited to large-scale colleting. In this case, the inside of the hairspring has no hook and its end is crimped to the collet (Figure 4). Such a construction does not allow correction of the attachment point.

Figure 4

“Greiner” collet

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Another industrial method of collet fitting consists in linking the hairspring to the collet by laser welding (Figure 5). As with the Greiner collet fitting, this method does not allow the attachment point to be corrected. However, it presents less risk of deforming the first coil.

Figure 5

Collet with laser welding of the hairspring

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The collet is pressed onto the upper part of the Balance staff. The fit must be strong enough for the collet to remain perfectly secured to the axis when the watch is running. A wide chamfer is present under the collet, facilitating its engagement onto the axis and easily allowing the collet to be removed from its axis without damaging the hairspring. The slit of a classic collet (Figure 3) allows the collet to be pivoted angularly on its axis during the construction of the regulation or to adjust the setting to the guide mark, notably for watches lacking a movable stud holder.

2. Artisanal manufacturing of a collet

The collet is a component that is easy to manufacture. A simple lathe and a small sensitive drill will be sufficient for its manufacture.

3. Industrial production of a collet

The collet is a component that is easy and quick to produce industrially. A few profile turning operations (turning, drilling, milling of the slot) are enough and involve a manufacturing cycle of only a few seconds.