Repairing damaged hairsprings
There are other studies on the website about small adjustments to hairsprings but, I received a very nice Eterna (Valjoux 22 based) calibre 703 watch with significant deformation of the spring which is of the flat design (not Breguet overcoil). It’s a real shame that sometimes these delicate parts get damaged but, it happens, and the first comment I try to make is “all these things can be fixed”.
The deformation is too much to resolve with the balance mounted in the movement so, it’s taken out. With the balance removed from the cock, the spring looks like this. It’s been pulled out of shape between the stud and the regulator pins. The rest of the spring is fine and this issue can typically be resolved without new parts.
It takes a delicate touch to be able to shape these which you only develop with time. A little time later and the spring looks like this. It’s not finished but is closer to being the correct shape.
The next is to trial fit it back to the movement to estimate the position of the outer coil so it will fit centrally in the regulator pins over the range of adjustment of the regulator. After that, a further adjustment and it looks like this. It’s clearly still not finished but it’s now easier to replace the balance in the movement and make the final adjustments with it mounted on the cock.