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Pinning Hairsprings

From Horology magazine, September, 1938

Pinning Hairsprings

Dear Sir:
Will you kindly publish an article on pinning a hairspring to the stud or collet in your next issue of Horology?

Answer: Pinning up a hairspring is an operation which is more a matter of skill than equipment. The first step in pinning a spring to a collet is to place the collet either on a broach or an arbor having a fin to prevent the collet from turning. Place the collet up side down so that in the event a slight scratch or other mark is made it will not show later. If the arbor is held in a horizontal position the spring will be nearly level when pinned.

Next insert the inner end of the spring in the hole of the collet and with a tweezer put in a hairspring pin as far as it will go. Pins used for regulators are . best for they have a more gradual taper and will hold better. Now check the spring to see if it is level before fastening the pin permanently.

If satisfied with its appearance grasp the small end of the pin with a fine flat pliers and pull it until it is forced tightly in the hole. Then by giving the pin one or two sharp twists with the plier break it off. If done right the pin will break off cleanly at the edge of the hole in the collet. The large end is then broken off in the same manner. So much for the collet.

The stud may be held in a pinvise, horizontally for convenience. The spring is inserted in the hole and the pin pulled tight with a flat pliers, just as described above. However, the pin is not broken off but is clipped with a fine cutting pliers so that there is a small excess on either side. The spring may be clipped off with the pin at the same time.

The tool shown in Fig. 2 is very convenient for holding collets while pinning springs. A broach is held in the center of a white disc by means of a set-screw.

The handle is hollow and contains a compartment for extra broaches of various sizes. It is manufactured by L. F. Acker, Springfield, Ill.

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