Staff replacement, balance wheel wobble

[VWatchie]

So, I've reached another major milestone on my journey in watch repair. I have now replaced my very first balance staff (Tissot calibre 781), and I feel pretty good about myself!

Replacing a balance staff is likely not the first thing you do when you start servicing and repairing watches as you need some expensive tools. Of course, you should also have developed some skill in handling small parts with tweezers. You also need the know-how, and that was mainly provided to me by my fellow Swede @HSL in my own language (Thank you very, very much!). There's also an excellent video on the watch repair channel which demonstrates in detail how to replace a balance staff. The video can be seen here.

Anyway, as you can see in the following video, the balance wheel wobbles:

I don't know if the wheel wobbled before I replaced the balance staff. The reason for the replacement was that one of the pivots on the original staff had broken off. I should mention that end shake and side shake look pretty perfect.

So, I have some questions:

1. Is the wobble severe enough to affect timekeeping? If so, how much and in what way?

2. Would a truing caliper like this one be the tool of choice to rectify the wobble? I do not yet own a truing caliper and it is a pretty expensive tool.

3. I intend to poise the balance statically on my poising tool, but will it be worthwhile as long as the balance wheel wobbles?

 

Edited May 14, 2021 by VWatchie

[JohnR725]

At the link below go down to the School of watchmaking section unit two covers truing of balance wheels. Then look on eBay or somewhere else that prices quite interesting were basically it seems extremely high. Of course maybe I'm out of touch with reality of current tool prices as they used to not cost that but maybe there is no demand.

Then I've seen worse and probably everything not perfect on the balance will have an issue but you might as well just go ahead and see what happens. It's more of a problem of its out of round wobbling I don't actually know how much would bad timekeeping results in a wobble like this other than visually it doesn't look nice.

 

https://mybulova.com/vintage-bulova-catalogs

 

 

[HSL]

Practice makes perfection as some dude once said.
I wouldn't think it would affect the timekeeping only the wear of the balance pivots, if it runs to dty  the pivots will wear down a bit but it will take years and years like with the original one.
Hard to say if it is the rim of the balance that wobbles or the fact the riveting is uneven. With the truening caliper and your stakes one could investigate this by turning caliper find out the low point and gently with the flat stake give it a little punch.
Most of the times it will get better with some patience.

 

[Nucejoe]

 You now have imbalanced mass distribution around the staff, therefore the wheel's inertia is not balance affecting oscilation for sure, may rub with H/S, increases positional variation and brings additional instability on wrist, as for how much , not much.

 I usually put the fork cock back on, see that the rim clears the fork cock. this one looks like it will clear, then turn the wheel by hand to locate the low/ high points with respect to fork cock,  ink mark the spot. take the balance out, grab the opposit side of the spot in a sturdy tweezers and lift or lower the spot you have ink marked, put the balance back on mainplate, check the wobble and repeat. This can be made flat to a good degree, nothing acceptable for a chrono grade , but will do until you get you them expensive tools.

[VWatchie]

5 hours ago, HSL said:

I wouldn't think it would affect the timekeeping only the wear of the balance pivots, if it runs to dty  the pivots will wear down a bit but it will take years and years like with the original one.

This is interesting, the original 0.9 mm in diameter cap jewels were quite excavated. More so than I've ever seen before so I have replaced them. Perhaps the explanation for the pits in the cap jewels (except for being perfectly dry and dirty) is that the balance was already wobbling before I replaced the balance staff!? Anyway, that's what I'd like to think, meaning I made an excellent job replacing that staff! 

5 hours ago, JohnR725 said:

Then I've seen worse and probably everything not perfect on the balance will have an issue but you might as well just go ahead and see what happens.

I think I will do that and meanwhile research the market for truing calipers and read the "Unit 2 - Truing Balance Wheels" that you linked to.

EDIT: The pits in the cap jewels were somewhat wider in diameter than the pivots.

Edited May 14, 2021 by VWatchie

[rodabod]

Sometimes you can correct that out-of-trueness by going again with a flat/hollow punch on the rivet. A monometallic balance itself is less likely to be out-of-true. 

[HSL]

9 hours ago, rodabod said:

Sometimes you can correct that out-of-trueness by going again with a flat/hollow punch on the rivet. A monometallic balance itself is less likely to be out-of-true. 

This is what I think is going on here, since it is the first time one usually don't hit the domed stake firmly enough, one should ofcourse not whack it like with a sledgehammer. Just gentle and firm enough to spread the rivet out. A good fit on the stakes are crucial too, a nice and snugg fit is to be prefered.
It is very important to rotate the balance while spreding the rivet, this is done to even out the tension and by that getting the balance evenly attached.
In @VWatchie s photo one might see that the rivet isn´t there yet one can sense some sharp edges sticking up, some work remains to be done. As said befor when it is correctly in place it will most likely be much better.
But a darn good first attemt this far 

 

Edited May 16, 2021 by HSL

[VWatchie]

4 hours ago, HSL said:

In @VWatchie s photo one might see that the rivet isn´t there yet one can sense some sharp edges sticking up, some work remains to be done. As said befor when it is correctly in place it will most likely be much better.

Wow, thanks for the additional input! 

I've been looking at that rivet repeatedly, but not really knowing what to look for I thought some additional pictures from different angles might help determine if more "banging" needs to be done. When getting this close with the macro lens it's difficult to get perfect focus with the equipment that I've got, and lighting can play a prank on us. Anyway, here they are...

When I did the hammering, @Mark's words from the video were ringing in my ears: "As you can see, I'm not going to town on hammering away". He also speaks about the risk of splitting the staff. Good advice, but all this made me pretty nervous so I only used as much force as I dared while continually rotating the balance. Anyway, I ordered two staffs just in case I would fail on my first attempt.

So, if the pictures help to determine if more work needs to be done, which punches should I be using (narrow flat, wide flat,  narrow domed, wide domed) and in what order? As I have that extra staff I'm ready sacrifice this one to learn more about how much force is required.

As always, the input from you guys is just invaluable to me! 

 

Edited May 16, 2021 by VWatchie

[JohnR725]

At the link below you'll find the section titled Joseph School of Watch Making You want to download the whole thing in real life and read everything but in the meantime the first section would be useful. Then to get you started I snipped out an image.

Then it's not just putting in the staff that screws up the thing being level it also depends on how you got the old staff out.

The procedure is as simple as the pictures show. At least it's supposed to be. First one punch to make sure the balance wheel is down where it's supposed to be. Second punch to spread the rivet and a lot of times as I'm doing Biggerstaff's all use several punches here to spread the rivet slowly working outwards. Then follow up with the flat punch to make sure everything is nice and smooth.

 

https://mybulova.com/vintage-bulova-catalogs

[HSL]

I think you are the only who can see if the rivet made a good and even spread.
I mostly only use two stakes, I see you say narrow and wide. I guess the black art of this staking business is like taking your driver’s license, in the beginning you do all by the book but thirty years later you picked up some bad habits.
With the risk of getting bombs sent to me by mail I try to show with some illustrations, which don’t need any focus set, and which shows approximately what should happen with the rivet.
A too wide flat punch is not any good thing as you might end up hitting the balance instead.if the stake hits the spoke it might turn it slightly upwards.
The tip of the stake should go inside the small chamfer on the hole.
I intentionally have a different color on the balance shoulder so one know which part of the balance to concentrate on.

After giving it a bunch of gentle but firm taps the doomed stake should have begun to spred the rivet shoulder.
If not the stake is just a bit to small. But it should be a snugg fit. Rotate the balance to get a even spred and tension.

Finish of with a nice and snugg flat stake. You still have to rotate it around. When done you will be able to see the rivet shoulder bent down with a close fit to the chamfer of the hole.

I hope these illustrations gives you an idea what to look for.

And just in case my vocabulary differs from your or someone’s else’s I attach a drawing of a generic balance with some definitions on here too.

Now I think I go back to my 3D printer.....
Lol well saw John answered at the same time too.

 

 

Edited May 16, 2021 by HSL

[VWatchie]

49 minutes ago, HSL said:

l I try to show with some illustrations,

These illustrations are some of the best I’ve ever seen! Just awesome stuff and will be appreciated by many to come!  

They make the process and what should happen crystal clear. I’ll take a close look in my stereo microscope to assess the situation.

The illustrations also make it perfectly clear what punches to choose, something that gave me a lot of headache. So, just brilliant!

I’ll report back as soon as I’ve had a chance to look into it. Again, thanks!

 

Edited May 16, 2021 by VWatchie

[VWatchie]

I have now taken a very long and hard look at the rivet through my stereo microscope and there's no doubt. The rivet has been spread evenly and flattened so that the rivet is in level with the spokes. No part of the rivet is protruding over the hole in the balance. So, I'm happy with what I see! 

1 hour ago, HSL said:

A too wide flat punch is not any good thing as you might end up hitting the balance instead.if the stake hits the spoke it might turn it slightly upwards.

Indeed, and I think that's exactly what might have happened! I selected the widest punch I could find that would still fit snugly over the collet shoulder. That could very well explain the wobbling of the wheel. I will be assembling the movement without trying to rectify this wobbling (which isn't too bad), but long term I will make that another goal and will try to rectify it.

Anyway, the next time I replace a balance staff I will know exactly how to go about it, what tools to use, and perhaps most importantly, exactly what to look for. The knowledge I've gained is what really matters. I really can't thank you (and other WRTers) enough!

[ifibrin]

Could the side-shake in the cap jewels, coupled with a slightly off-level hairspring cause slight wobbling, only perceptible at high (i.e. 10 times) magnification? de Carle in “Practical Watch Repairing” mentions that the side shake of the balance wheel in the cap jewels should be up to 5 degrees from the perpendicular of each side of the staff, which would certainly allow for a slight wobble if the hairspring wasn’t perfectly parallel to the axis of rotation.  

I admit this question is purely academic, since this would have no effect on the time keeping of the watch.