Mechanical WW Need help ordering balance

[Charlie Ryan]

Hi All

I'm a very new hobbyist. I have a Bifora 115/1 with a bent hairspring. I dont have the skill to fix it.

Borel doesn't stock Bifora. Cousins UK lists parts for 115 and 115.1. Is point one the same as slash one?

under 115.1 they have "Balance Complete, Ordinary, Bifora 115 721"

under 115 they list these below

balance complete, ordinary and shockproof, bifora 115 723
balance complete, ordinary, bifora 115 721
balance complete, shockproof, bifora 115 721.1

Which one is likely the correct one?

Thank you

Charlie

 

[Chris Radek]

balance complete, shockproof, bifora 115 721.1

Your movement is definitely shockproof, looks like a diashock setup or similar. So you need a balance with a matching shockproof staff.

I think the 721.1 is most likely to be the balance complete for shockproof. I think if you order the one that says "balance complete ... 723" you may get just a staff, 721 is the swiss part number for balance complete with flat hairspring, 722 is balance complete with overcoil, 723 is (plain) staff only.

The bestfit books have a dictionary at the front showing these generic swiss part numbers.

That all being said, that hairspring looks damaged at the outermost coil only, and with the right technique and patience I bet you could fix it. Pop the spring off the balance, attach it to the cock, and work those bends out. Where there's an unwanted sharp bend sometimes you can fix it by just squeezing the bent spot between some flat-nosed tweezers like a 2a style. You'll know you're done adjusting the outer coil when you can move the regulator and the collet stays centered over the jewel.

Mark the balance with a sharpie dot where the stud points before you take the spring off (if there isn't already a mark - sometimes there is), so you can put it back in about the same place. You'll probably still have to adjust the beat afterwards. You can then wipe the sharpie off with alcohol on a q-tip.

 

[Smudgy]

Chris is right about attempting to straighten the spring, especially if you are just going to throw the whole thing out anyway. It looks like you have four places on the outer coil that need attention (the one bend is there to bring the outer coil away from the other coils so that the regulator doesn't touch the rest of the spring during vibration). It is probably one of the best situations to start with if you have any desire to learn hairsprings.

The stud point will probably move a little once the spring is straightened. But the arm that holds the stud will rotate to put the watch in beat if needed, though you don't want to move it far if it can be helped. You may want to note where the split in the collet is located, as that shouldn't move at all.

 

[Skutt50]

I agree with Smudgy that it would be possible to rescue the hairspring.

Before attempting any adjustment I would set the regulator arm to the slow position and check where the hairspring ends up. Then adjust the hairspring (on the stud side) so the hairspring rests in the middle of the regulator pins. Then move the regulator arm and obeserve where the rest of the bends are......

My guess is that you need to make some adjustments at 11 and 1 o'clock in your picture......

Use the finest tweezers you can find and when you bend the hairspring you need to hold the tweezers 90 degrees from the flat of the hairspring. If you hold them at any other angle you may end up with a hairspring that is not flat anymore! (I use some twezers with tips that are tilted/bent 45 degrees which makes this easy.)

To straighten a bend it is often enough to just squeeze the bend with the tweezers, but if you need to create a bend you nee to push on the hairspring with e.g. a small needle or another pair of tweezers........

Work in short intervalls (5-10 minutes) and work slow. It is better to repeat than to reverse a move.

You can always start and post new pictures for more hints on how to proceed.......

 

[Charlie Ryan]

Thanks All,

I'll attempt it and report back.