Omega T12.6 (1930s): adjusting the lower balance jewel to reduce endshake?

[Knebo]

Hello everyone,

I've been working for a while on an Omega T12.6 from the 1930s. It's been challenging. It came to me with a badly set original mainspring (it was barely larger than the barrel when I took it out ). The beat error was 6ms and I re-adjusted the position of the collet and brought it down to about 1ms -- I'm happy with that. The regulator pins were so open that the hairspring wasn't actually in them at all. I adjusted that too. 

I now get some deceivingly nice results in the dial up position. 310° amplitude and perfect trace. (Before anyone asks, I verified all amplitude readings via slow-motion videos. I also deducted an approximate lift angle of 49°)

HOWEVER, 

1. In the dial down position, amplitude drops by ~25° and the rate also changes a bit too much. I'm sure that this is not due to lubrication differences (I checked and redone it with same results). I think the regulator pins are fine and not the culprit.

2. The vertical positions are bad... I loose between 60 and 100° of amplitude and rates go plus or minus 60sec/day. Overall delta is 130sec. (a little observation: after changing the position, the rate changes quite dramatically [and amplitude drops] at first, but then slowly settles after 1-2 minutes or so [and amplitude also recovers a little bit]). But the traces are relatively clean (but not perfect).

There are certainly some poise issues, but I think it's first an issue of sideshake and endshake of the balance wheel. I can move it up/down, and even a bit sideways. 

I have looked at the balance staff and its pivots -- and I think it's fine. Sorry, I don't have a microscope for useful pictures -- you'll have to take my word for it.

 

I see one think I could do: move the lower balance jewel upwards towards the balance to reduce the shake. However, that would increase the distance between the two jewels (as the cap jewel is screwed on in a fixed position from the other side. A slightly larger distance between the two jewels would be the result. See pictures. What do you think? Worthwhile the risk?? As I have little experience with jewel adjustments, it's a risky operation for me. Spare parts for this movement seem impossible to get.

I could also accept it as it is. It's 90 years old and a tiny movement (12.6 x 21.9mm). And after all, I do still get over 180° amplitude in all positions after 24h. And I think it can be regulated to "real life" usage. I feel like I've a achieved a lot for MY level of skills (moving collet and bending regulator pins+hairspring) and I'm afraid of spoiling it all IF there is not a high level of confidence that this will actually help.

 

 

Dial up

Dial down

Crown right:

 

 

For reference, the whole watch and the whole movement:

 

[RichardHarris123]

You could try shimming the balance cock, if it doesn't work just remove the shim.

[Knebo]

7 minutes ago, RichardHarris123 said:

You could try shimming the balance cock, if it doesn't work just remove the shim.

Thanks for the suggestion, but wouldn't that increase the endshake where I thought of reducing it?

[RichardHarris123]

If you shim the end towards the outside edge of the movement, it should tip the balance end down.  Might be a  bad idea but worth a try. 

[rehajm]

The jewel in the plate looks to be flush already- is there room to move it up?

Is your cap jewel tight?

The risk in the pushing is having the jewel no longer fit. Similarly, on a practice watch I an trying to adjust the shake of an escape wheel and I pushed out a sliver of metal from the hole. Now I have to try and ream and get a larger jewel or go the bushing route. I'm learning too so will give the a larger jewel a go when it arrives...

[Knebo]

15 minutes ago, rehajm said:

Is your cap jewel tight?

Yes

15 minutes ago, rehajm said:

The jewel in the plate looks to be flush already- is there room to move it up?

Good point. Not sure. I was thinking only of the tiniest push, of course.

Thanks @rehajm. 

[rehajm]

Just now, Knebo said:

Good point. Not sure. I was thinking only of the tiniest push, of course.

Give it a go- good luck...

[Nucejoe]

 I think your on the right path, that is;  pivot shoulder SEAT  comes in contact with balance jewel and  as a result drops the amplitude.

To test this theory you need to reduce and adjust end shake on balance pivot, so  flip the cap stone over to face its convex side to the pivot. 

The cap stone is fitted in cap stone plate/spring which screws onto the main plate,, so as a first test don't move or flip any stone, just flip the cap stone plate over  ( with the cap stone not moved)  , then see if you gain amplitude.

What Richard says might work too.

 

Edited September 6, 2023 by Nucejoe

[Knebo]

27 minutes ago, Nucejoe said:

 I think your on the right path, that is;  pivot shoulder SEAT  comes in contact with balance jewel and  as a result drops the amplitude.

To test this theory you need to reduce and adjust end shake on balance pivot, so  flip the cap stone over to face its convex side to the pivot. 

The cap stone is fitted in cap stone plate/spring which screws onto the main plate,, so as a first test don't move or flip any stone, just flip the cap stone plate over  ( with the cap stone not moved)  , then see if you gain amplitude.

What Richard says might work too.

 

This is a very interesting and helpful trick to test the idea!! Thank you. 

It makes me think, though: if I only move the balance jewel (but not the cap jewel), I'd reduce endshake but actually force even more contact with the pivot shoulder seat, no? Wouldn't I also have to move the cap jewel (inside the small screw-in plate on the dial side)? 

EDIT: the trick to test won't work. The cap stone in the plate is recessed a bit on the convex side. In other words, turning it around will actually move it further away from the balance jewel (instead of moving it closer). 

Edited September 6, 2023 by Knebo
New info

[rehajm]

1 hour ago, RichardHarris123 said:

f you shim the end towards the outside edge of the movement, it should tip the balance end down.

I didn't understand this at first but see you are using the shim to push the pivot end lower...interesting...

[Nucejoe]

1 hour ago, Knebo said:

It makes me think, though: if I only move the balance jewel (but not the cap jewel), I'd reduce endshake but actually force even more contact with the pivot shoulder seat, no? Wouldn't I also have to move the cap jewel (inside the small screw-in plate on the dial side)? 

 

Right , you'd reduce the end shake or(  the distance between upper and lower balance jewels) but might force more pivot shoulder seat to jewel contact or might not depending on the actual seen of crime. 

That the cap stone's  convex side is recessed,  It still might reach the pivot as its convex ÀND  the screw- palte is a spring.

if they don't reach, then  end stones  can also be moved, if its receced it can be move flush livel with the screw-cap stone plate.

There is also a chance non of the above work, which means only one thing,    PIVOTS WORN BEYOND HOPE AND BALANCE COMPLETE MUST BE RE-STAFFED.     

                                          OR 

Get the balance mounted on lathe to elongate the pivot length.

Shimmed cock can be unshimmed,  no worries ,its reversable.

Edited September 6, 2023 by Nucejoe

[Knebo]

2 hours ago, Nucejoe said:

That the cap stone's  convex side is recessed,  It still might reach the pivot as its convex ÀND  the screw- palte is a spring.

if they don't reach, then  end stones  can also be moved, if its receced it can be move flush livel with the screw-cap stone plate.

Unfortunately, the end stone on the scew-plate is already flush on the balance side and the convex side does not protrude enough to make up for the recess. It doesn't reach further than the flat side. 

 

2 hours ago, Nucejoe said:

There is also a chance non of the above work, which means only one thing,    PIVOTS WORN BEYOND HOPE AND BALANCE COMPLETE MUST BE RE-STAFFED.   

While I did write that the pivots are ok, you may still be right here. I only verified that they are straight (and actually there). But I don't know about their supposed length. It could be that it has worn down gradually and in a straight manner. I've already ordered a replacement staff and will compare. 

While I really want to do the staff replacement with my new staking set, it would be my first staff replacement. And given that it seems impossible to get a replacement balance (if I fail), I don't dare to do it (yet). 

[Nucejoe]

Check  both pivots under good magnification, a worn/ damaged pivot is noticably shorter  than the other.

You are not loosing amplitude in both FU & FD position, which generally indicates  only one pivot is shorter if any.

A clear close up of the pivots helps diagnostic and useful for future references, there are also pics posted in previous discussions, sorry I can't find one to refer to.

Haha,  I know,  staff replacement is scary.

Good luck pal.

Edited September 6, 2023 by Nucejoe

[Ronp]

I think, also given the serious drop in amplitude in the vertical positions (and likely therefore also in the rate hige difference) are signs of a worn or damaged balance staff. If you have the skill and tools I, myself, would first replace the balance staff now. All other suggestions look to me introducing a fault to correct a fault.

At a seconfd level You might also want to have look the pallet fork and position of the limiting pins of the pallet fork. If they are not straight up and your drops etc from the pallet stones on the escape wheel are not equal you could also have the symptons you decribed.

[JohnR725]

3 hours ago, Ronp said:

I, myself, would first replace the balance staff now. All other suggestions look to me introducing a fault to correct a fault.

The normal classic rule in watch repair is not to modify the watch to fit the part. Because someday somebody might replace a balance staff and wonder why they're having an issue because somebody modified the watch to fit their situation as opposed to just fixing the problem in the first place. Of course you do have to identify what the problem actually is..

Then just a reminder what does the balance jewel look like and why your shoulder will never ever touch the jewel if it does your having a serious problem.

Now that you see with the jewel looks like let's see what your pivots are supposed to look like in the jewels

As you can see normally it should be impossible for anything other than the pivot itself to touch the jewels if the cone shaped Part of pivot is touching the pivot is way too short and the balance staff should be replaced.

Oh and when you're looking at the pivots notice how the ends are only slightly rounded. If your balance staff pivot has ends that somebody polished nice and round to reduce the friction you end up with too much amplitude on the ends in the pivot versus the sides and it leads to goofy timing because you have huge amplitude differences. The typically the balance pivot is just slightly rounded. Usually when you're seeing dial up and down amplitude issues in addition to the jewels in the usual thing you look at the pivots are they shaped identical. Or in the case of pocket watches if you look in you see a winking affect. Often times of the watches been dropped the pivot will have a flat spot and when you look in the flat spot catches the light it winks at you not a good thing at all.

Oh and remember the golden rule of not modifying the watch? Here's an example somebody has modified your watch notice the items I circled if you look carefully somebody has pushed on the metal to raise it up just a little bit because they probably change the balance staff and that was a hair too long.Which as I said modifying the watch leads to confusion for future watch repair

 

[Knebo]

Thanks! 

9 hours ago, Ronp said:

All other suggestions look to me introducing a fault to correct a fault

 

5 hours ago, JohnR725 said:

because somebody modified the watch to fit their situation as opposed to just fixing the problem in the first place

Yes, absolutely right. I've decided not to touch the jewels. 

 

 

Ohhh, well spotted @JohnR725!! That might just be the source of the problem and even replacing the balance staff would then not have helped. I could file this off and maybe that will solve it. 

5 hours ago, JohnR725 said:

Oh and remember the golden rule of not modifying the watch? Here's an example somebody has modified your watch notice the items I circled if you look carefully somebody has pushed on the metal to raise it up just a little bit because they probably change the balance staff and that was a hair too long.Which as I said modifying the watch leads to confusion for future watch repair

 

 

[VWatchie]

I don't know if it has already been mentioned in the thread (apologies for not having read it all), but have a look at the flat surface of the cap jewels to make sure they haven't been pitted where the staff pivot meets the surface. I don't know what you would do about it in this case though.

[Knebo]

24 minutes ago, VWatchie said:

I don't know if it has already been mentioned in the thread (apologies for not having read it all), but have a look at the flat surface of the cap jewels to make sure they haven't been pitted where the staff pivot meets the surface. I don't know what you would do about it in this case though.

Thanks for taking the time to respond! 

I checked them and they are ok. 

[Nucejoe]

2 hours ago, Knebo said:

Ohhh, well spotted @JohnR725!! That might just be the source of the problem and even replacing the balance staff would then not have helped. I could file this off and maybe that will solve it. 

 

 What if you filed off those bumps and " it didn't slove it " .

Again, a test.  Add shim ( aluminim foil is good )  to the outer circumference of the mainplate under the cock,  to compensate for the bumps and see if it helps.

Shimming can give down to .01 mm accuracy, you can fold the foil two folds or three , once you place the cock on top of the shims and tighten the cock screw and check the end shake,  you can loosen the screw and slide the shims inward & outwards the center of mainplate, thats how you can adjust end shake on the balance to incredibly high degree of accuracy.

You should  fix the mess previous watch destroyer made.

 

12 hours ago, Ronp said:

 I, myself, would first replace the balance staff now. All other suggestions look to me introducing a fault to correct a fault.

Would you gurantee a new staff will definately solve the problem, gurantee in writting please.

We are dealing with collection of problems made by previous watch destroyers, faults are not totally diagnosed.

Knebo, to check for insufficient end shake , just loosen the cock screw, insufficient end shake can put  just enough pressure on pivots to let the oscilator run yet also limit its amplitude.

[Neverenoughwatches]

8 hours ago, JohnR725 said:

Here's an example somebody has modified your watch notice the items I circled if you look carefully somebody has pushed on the metal to raise it up just a little bit because they probably change the balance staff and that was a hair too long.Which as I said modifying the watch leads to confusion for future watch repair

Note to Knebo. I've seen and done this myself on something cheap as a bit of an experiment.  known as gouging done with a small pointed tool. Considered a bodge technique but can work to degree not that even i would condone it. Particularly done this way would angle the cock, that might impact the sideshake on that pivot.

3 hours ago, Knebo said:

Ohhh, well spotted @JohnR725!! That might just be the source of the problem and even replacing the balance staff would then not have helped. I could file this off and maybe that will solve it. 

 

1 hour ago, VWatchie said:

I don't know if it has already been mentioned in the thread (apologies for not having read it all), but have a look at the flat surface of the cap jewels to make sure they haven't been pitted where the staff pivot meets the surface. I don't know what you would do about it in this case though.

No it hasn't been mentioned watchie, another good point raised . That would increase endshake.

50 minutes ago, Nucejoe said:

 What if you filed off those bumps and " it didn't slove it " .

Again, a test.  Add shim ( aluminim foil is good )  to the outer circumference of the mainplate under the cock,  to compensate for the bumps and see if it helps.

Shimming can give down to .01 mm accuracy, you can fold the foil two folds or three , once you place the cock on top of the shims and tighten the cock screw and check the end shake,  you can loosen the screw and slide the shims inward & outwards the center of mainplate, thats how you can adjust end shake on the balance to incredibly high degree of accuracy.

You should  fix the mess previous watch destroyer made.

 

Would you gurantee a new staff will definately solve the problem, gurantee in writting please.

We are dealing with collection of problems made by previous watch destroyers, faults are not totally diagnosed.

Knebo, to check for insufficient end shake , just loosen the cock screw, insufficient end shake can put  just enough pressure on pivots to let the oscilator run yet also limit its amplitude.

The shims are a better idea that lift the balance cock evenly, cheap tin and foil finishes at around 0.01mm, but there are thicker better brands if needing for height. The gouging marks can compress over time.