Any ideas what could cause a wildly fluctuating rate?

Archer · Feb 21, 2021

S.H.
So, assuming is is demagnetized.

Did you check that the watch keeps reasonable time? Because if the mainspring is only slightly too strong, rebanking can happen only dial up or dial down, at full wind. As soon as friction increases and the spring unwinds, it can disappear. Impact on timekeeping may be slight.

Of course if the mainspring is really too strong, it happens on all positions and not only at full wind. Big impact on timekeeping if it is regularly rebanking.

If the hairspring is sticky, deformed, out of the regulator, or if a small hair is tangled in it, you can have all sort of weird stuff happening, but usually on all positions, full wind or not. Two coils touching, in particular, may induce weird rate variations if they come in contact and stick at high amplitude. Usually, also a visible impact on timekeeping.

So, you may check what happens at full wind, half wind, dial up and on the side. But without opening it you may not be able to know much more... had to diagnose anything remotely.

Not sure if you regularly service 321's, but with a factory mainspring I've had them rebank for hours on end. As in still rebanking the following day...

The thing that can fool you sometimes is that immediately after winding, it might not rebank. It tends to start after the watch has been sitting for a while. My guess is that this happens because when the torque is very high, something is tipping slightly causing a bit of extra drag. As the torque drops a bit, this effect goes away and the amplitude actually goes up. I've seen this quite a few times, and this movement is, in my experience, very sensitive to rebanking with the amplitude at the high end.

Andy F · Feb 21, 2021

Lower Balance jewel issue? Kind of moot though if you can't open it.

S.H. · Feb 21, 2021

Archer
Not sure if you regularly service 321's, but with a factory mainspring I've had them rebank for hours on end. As in still rebanking the following day...

The thing that can fool you sometimes is that immediately after winding, it might not rebank. It tends to start after the watch has been sitting for a while. My guess is that this happens because when the torque is very high, something is tipping slightly causing a bit of extra drag. As the torque drops a bit, this effect goes away and the amplitude actually goes up. I've seen this quite a few times, and this movement is, in my experience, very sensitive to rebanking with the amplitude at the high end.

No, not very regularly. Interesting to know... and to watch for!

M'Bob · Feb 21, 2021

Archer
The thing that can fool you sometimes is that immediately after winding, it might not rebank.

This appears to be exactly what happened.

François Pépin · Feb 22, 2021

Archer
Not sure if you regularly service 321's, but with a factory mainspring I've had them rebank for hours on end. As in still rebanking the following day...

The thing that can fool you sometimes is that immediately after winding, it might not rebank. It tends to start after the watch has been sitting for a while. My guess is that this happens because when the torque is very high, something is tipping slightly causing a bit of extra drag. As the torque drops a bit, this effect goes away and the amplitude actually goes up. I've seen this quite a few times, and this movement is, in my experience, very sensitive to rebanking with the amplitude at the high end.

Hello Al,

Thank you, again, for your knowledgeable comments!

I was wondering what would be your standard practive in the case of a rebanking? I do not have this issue often, but would be glad to know...
When I face this issue, I changed the oil on the pallets for a heavier one. I read this could be an answer and it did the job, but I am not sure now it was the best practice...

Cheers,
François

Archer · Feb 22, 2021

François Pépin
Hello Al,

Thank you, again, for your knowledgeable comments!

I was wondering what would be your standard practive in the case of a rebanking? I do not have this issue often, but would be glad to know...
When I face this issue, I changed the oil on the pallets for a heavier one. I read this could be an answer and it did the job, but I am not sure now it was the best practice...

Cheers,
François

Hi François,

It depends...I know I say that a lot, but seems there rarely is there a universal answer to questions like this.

If I consult Omega's guidance, it's not much help. They say "replace the mainspring barrel", but of course for many watches I service mainspring barrels don't exist new, and my feeling is that this is guidance for automatic watches, rather than manual winding. For the escapement, I already use 9415, so I'm not aware of anything heavier than that - unclear what you are using there.

So there are a list of things that you can do, from the mild to the drastic...

1 - Change oil in the balance jewels to something heavier - this can work if the rebanking is not severe.

2 - Use heavier oil in the train wheels.

Then we get into more difficult and more involved solutions...

3 - Find a weaker mainspring - I've yet to find a suitable one for a 321 with this issue. Some brands (Rolex for example) made weaker springs for this very reason, because many Rolex calibers will rebank at amplitudes where say a modern ETA would be just fine.

4 - Add weight to the balance - this has to be weighed against the other effects of this, so centering of the regulator for example. Of course this will not work on a watch with a smooth balance.

5 - If the lock on the pallets is very light, moving the pallet stones in can drop the amplitude, but again can have unintended consequences, so this is rather advanced work to both perform, and more so to understand all the implications of moving them.

6 - Blunt the ends of the balance staff - burnish a flat to drop the amplitude in the horizontal positions.

To me the last option here is pretty much butchery, but I've seen other watchmakers advocate this, but it would be an absolute last resort thing for me.

Now if we are referring to an automatic watch, then the first thing I would do is clean the barrel and use a less sticky braking grease. I use Kluber P125 braking grease, and it is VERY sticky. A friend of mine brought me the latest super duper Rolex braking grease to try, telling me that he had much better balance amplitudes with this compared to the old Rolex grease. When I tried it the amplitudes were way lower than what I get with the P125, so I use this as my "weak" braking grease when I need that.

Anyway, hope this helps. It can be a rather frustrating issue to solve.

Cheers, Al

François Pépin · Feb 22, 2021

Archer
Hi François,

It depends...I know I say that a lot, but seems there rarely is there a universal answer to questions like this.

If I consult Omega's guidance, it's not much help. They say "replace the mainspring barrel", but of course for many watches I service mainspring barrels don't exist new, and my feeling is that this is guidance for automatic watches, rather than manual winding. For the escapement, I already use 9415, so I'm not aware of anything heavier than that - unclear what you are using there.

So there are a list of things that you can do, from the mild to the drastic...

1 - Change oil in the balance jewels to something heavier - this can work if the rebanking is not severe.

2 - Use heavier oil in the train wheels.

Then we get into more difficult and more involved solutions...

3 - Find a weaker mainspring - I've yet to find a suitable one for a 321 with this issue. Some brands (Rolex for example) made weaker springs for this very reason, because many Rolex calibers will rebank at amplitudes where say a modern ETA would be just fine.

4 - Add weight to the balance - this has to be weighed against the other effects of this, so centering of the regulator for example. Of course this will not work on a watch with a smooth balance.

5 - If the lock on the pallets is very light, moving the pallet stones in can drop the amplitude, but again can have unintended consequences, so this is rather advanced work to both perform, and more so to understand all the implications of moving them.

6 - Blunt the ends of the balance staff - burnish a flat to drop the amplitude in the horizontal positions.

To me the last option here is pretty much butchery, but I've seen other watchmakers advocate this, but it would be an absolute last resort thing for me.

Now if we are referring to an automatic watch, then the first thing I would do is clean the barrel and use a less sticky braking grease. I use Kluber P125 braking grease, and it is VERY sticky. A friend of mine brought me the latest super duper Rolex braking grease to try, telling me that he had much better balance amplitudes with this compared to the old Rolex grease. When I tried it the amplitudes were way lower than what I get with the P125, so I use this as my "weak" braking grease when I need that.

Anyway, hope this helps. It can be a rather frustrating issue to solve.

Cheers, Al

Thanks a lot Al! Very usefull, as usual.

Last time I had to deal with rebanking, I was still using Moebius 8000 on the pallets, so I could change to a heavier oil. Now I have swiched to 9415 - I followed your advice here! But thanks to you I will have plenty of options to consider if I am to face this issue again.

Cheers,
François

Any ideas what could cause a wildly fluctuating rate?

Archer

Andy F

S.H.

M'Bob

François Pépin

Archer

François Pépin

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