CHAPTER VIII
RELATIVE PINNING POINTS OF THE HAIRSPRING
[29.]Original Springing of Watches.
Theory and practice agree that different models of watches have important relative points of attachment of the spring to collet and stud. In the original springing and adjusting of high grade watches, these points receive careful consideration, and only a very small percentage ever require future alterations.
There are instances, however, where the original allowance of position variation has been considerable, also medium grades where no attention has been directed to pinning points and in which an occasional alteration may be required before a close position rate can be obtained.
[30.]How Pinning Point Alterations are Made.
These alterations are generally made by breaking off or letting out a small section of the inner coil at the collet. In making such alterations a quarter of a coil broken away at the collet will have the same effect as will a quarter of a coil broken off at the outer end and will require less weighting of the balance to correct the mean time. It will also avoid breaking and remaking the over coil and the possible necessity of readjustment to temperature. Letting out the spring can be accomplished by unpinning and repinning the spring at collet with less of the coil entered in the pinhole. This is not a positive alteration, however, because very often the segment in the pinhole is as short as it can be with safety.
A more substantial correction is that of reforming the over coil in a manner that will cause the end holding the stud to be shifted further forward.
The method of obtaining this correction is illustrated in Fig. 8. The broken line shows the original formation of the over coil with the stud on the line "B". The solid lines show the corrections with the stud shifted to the line A.