Solid collet loose on Omega 625 - best fix?

[mikepilk]

I had to put a new balance staff in an Omega 625. I did a visual check before fitting, and it looked the same as the old staff.

It rivetted in as expected, and the roller fitted well, but then I found that the hairspring collet is very loose. 

The balance staff was sold as genuine Omega NOS from a trader I've used before. I have another staff from another trader, also sold as Omega NOS. The collet is equally loose on that one too. Both staffs look to be the quality you would expect from Omega.

It's a solid collet, so I cannot do the usual fix of closing the slot.

What's the best option. Try to close the holes - I'm not sure I have a stake with such a finely curved tip.  Shellac, Loctite ?

 

Edited July 11, 2024 by mikepilk
typo

[SwissSeiko]

easiest would be locktite on an oiler. proper way is probably shellac, but thats a tough place to work in with how quickly shellac hardens.

[mikepilk]

14 minutes ago, SwissSeiko said:

easiest would be locktite on an oiler. proper way is probably shellac, but thats a tough place to work in with how quickly shellac hardens.

It's so loose it rocks slightly. So I'd like to use shellac, but this is a small balance (hairspring only 3.5mm dia), and there's danger of getting shellac on the hairspring 

The smallest hole closing pusher in my jewelling tool looks like it should work. I'm tempted to try that to close the hole, then use Loctite.

[SwissSeiko]

6 minutes ago, mikepilk said:

It's so loose it rocks slightly. So I'd like to use shellac, but this is a small balance (hairspring only 3.5mm dia), and there's danger of getting shellac on the hairspring 

The smallest hole closing pusher in my jewelling tool looks like it should work. I'm tempted to try that to close the hole, then use Loctite.

do you have flake or stick shellac? If you have flake, you could put the smallest little flake at the base of the collet, then heat it up similar to a pallet warmer. Or maybe you could drop a flake in through the top opening and do the same thing? I can believe it isn't slotted. That's so strange.

Edited July 11, 2024 by SwissSeiko

[mikepilk]

7 minutes ago, SwissSeiko said:

do you have flake or stick shellac? If you have flake, you could put the smallest little flake at the base of the collet, then heat it up similar to a pallet warmer. I can believe it isn't slotted. That's so strange.

I have flaked shellac. I might try that. I have an old pocket watch mainplate I use. It has enough mass to keep hot for a while so I can work under the microscope. The pivot holes are useful for sitting parts in.

(BTW the movement has an adjustable stud holder, so I don't need to worry about aligning the collet)

Edited July 11, 2024 by mikepilk

[SwissSeiko]

3 minutes ago, mikepilk said:

I have flaked shellac. I might try that. I have an old pocket watch mainplate I use. It has enough mass to keep hot for a while so I can work under the microscope. The pivot holes are useful for sitting parts in.

(BTW the movement has an adjustable stud holder, so I don't need to worry about aligning the collet)

That's a good idea using the main plates! As far as alignment with the collet, you do need to be able to line up the roller jewel within the banking pins, so I would make sure that is in alignment, mark where the stud is on the radius of the balance wheel, and then you can cement it with the shellac. Its a lot easier to align is this way then to try and adjust the roller table since its pressed on quite tight.

[mikepilk]

I marked on the balance rim the positions of the roller jewel and stud before disassembly. As the stud holder is adjustable, I can adjust beat error, so don't need to be precise with positions.

I've just thought of a problem. With the roller fitted, the jewel might fall out when I heat the balance. But if I remove the roller to shellac the collet, it won't be easy to refit with the hairspring on.

[SwissSeiko]

24 minutes ago, mikepilk said:

I marked on the balance rim the positions of the roller jewel and stud before disassembly. As the stud holder is adjustable, I can adjust beat error, so don't need to be precise with positions.

I've just thought of a problem. With the roller fitted, the jewel might fall out when I heat the balance. But if I remove the roller to shellac the collet, it won't be easy to refit with the hairspring on.

That is true. In that case, could you put the shellac here and heat it from above with a torch?

 

[RichardHarris123]

I would try a modern adhesive, I  have now barricaded the doors and windows awaiting the men with pitchforks.  

[mikepilk]

1 hour ago, RichardHarris123 said:

I would try a modern adhesive, I  have now barricaded the doors and windows awaiting the men with pitchforks.  

(Puts on tin hat) I have UV activated resin. That should work well.  and I believe it can be dissolved in IPA or acetone if necessary.

[Nucejoe]

 Not just the hairpsring , but the pivot must be cleanest with no adhesive on it.

1- I smear a bit of shellac on  base of the pivot,

2-Let dry,

3-Shave off ( with safety razor blade) any shellac that's not where its suppose to be. in case any adhesive  has got on pivot,  clean entirely  and try again.

4- Press the collet onto the pivot, make sure no shellac has got  on the wrong part,

5- Apply heat ( soldering gun) to the collet, until shellac re-melts, the melted shellac fills all available cavities. 

You can also steal nail polish from the lady and follow the same procedure except no need for heat. Nail polish does not damage metals.  

[mikepilk]

I only have shellac flakes, so I'll have to dissolve some.  Then using the soldering iron sounds a safe way. 

EDIT

I've just discovered why the new collet is so loose on both new staffs. The old staff measures 0.45mm diameter at the collet. The spec is 0.42mm

 

Edited July 11, 2024 by mikepilk

[Nucejoe]

 I am not sure if heat deforms pivots when doing this, so I try to carefully apply heat to the collet only. 

 Nail polish is the safest I know of, have not seen any sign of chemical damage to the metal by nail polish applied 50 years ago.