St 97 Balance stopping when screwed down

[enz0]

Hi everyone,

Currently working on an st97. Movement has been cleaned and lubricated and appears to be running strong when balance is inserted however it will stop when the screw is fully tightened. Balance immediately kicks up again if loosened by even a quarter turn. Thought it might have something to do with cap jewels being incorrectly placed but I've checked both sides several times i don't think it's that. Balance pivots are healthy with no bend at all. I'm still quite new to fault finding and diagnosis so any help on where to start looking would be appreciated. 

Thanks!

Edited February 5 by enz0

[AndyGSi]

Does this happen both with and without the fork?

Photos of what you've mentioned would help.

[watchweasol]

Hi was the watch running before the service ?  Because the symptoms you describe would point to lack of end-shake on the balance staff. Best to power down the movement remove the fork and try the balance on its own using a blower to power the balance, it should rotate for some time quite freely.

[ColinC]

Mark posted this video - which might explain what your are seeing in an extreme case

 

[enz0]

5 hours ago, watchweasol said:

Hi was the watch running before the service ?  Because the symptoms you describe would point to lack of end-shake on the balance staff. Best to power down the movement remove the fork and try the balance on its own using a blower to power the balance, it should rotate for some time quite freely.

Hi thanks for the response. When I got the watch it was running really low amplitude and around +400seconds per day so I thought it just needed a service at first. I did notice that the balance wasn't spinning as freely as it should be when I put it back on the mainplate for cleaning

[enz0]

9 hours ago, AndyGSi said:

Does this happen both with and without the fork?

Photos of what you've mentioned would help.

Without the pallet fork the balance does run but very slowly

[AndyGSi]

25 minutes ago, enz0 said:

Without the pallet fork the balance does run but very slowly

So how long does it run for if you rotate it 180deg and then let go?

[enz0]

7 minutes ago, AndyGSi said:

So how long does it run for if you rotate it 180deg and then let go?

At most 2-3 seconds and even then it's not very smooth

[AndyGSi]

49 minutes ago, enz0 said:

At most 2-3 seconds and even then it's not very smooth

Can you post photos of the pivots and jewels.

[Neverenoughwatches]

1 hour ago, enz0 said:

At most 2-3 seconds and even then it's not very smooth

With the balance cock screwed down does the balance have any up and down -side shake-  movement ? 

[enz0]

8 hours ago, Neverenoughwatches said:

With the balance cock screwed down does the balance have any up and down -side shake-  movement ? 

Fully tightened the balance wheel has no side shake at all and very little up and down

[enz0]

8 hours ago, AndyGSi said:

Can you post photos of the pivots and jewels.

A little hard to show but as you can see pivots on both sides are healthy

 

[AndyGSi]

Sorry but I can't tell anything from those photos.

[Knebo]

9 hours ago, Neverenoughwatches said:

up and down -side shake-

I guess you meant endshake. Posting past you bedtime? 

 

1 hour ago, enz0 said:

very little up and down

This "very little" maye just be the shock settings doing their job. 

 

19 hours ago, ColinC said:

Mark posted this video - which might explain what your are seeing in an extreme case

Have you checked this? I'm quite sure that's your issue. 

[enz0]

20 minutes ago, Knebo said:

I guess you meant endshake. Posting past you bedtime? 

 

This "very little" maye just be the shock settings doing their job. 

 

Have you checked this? I'm quite sure that's your issue. 

That's what I was thinking about the "very little" part. And yes i did check that video, I made sure the jewels were in the correct spot and I did notice that there was a mark similar to that of the one in the video however I'm not sure how to make that mark more prominent as I've never done something like that before. Any ideas?

[clockboy]

Reading through this post I would say at some time in its life it has had its balance staff changed and it is a tad to long.  As quick fix if the new staff is to long what is added is a thin shim under the balance cock or some create a notch in the plate., Both of these methods work but are a bodge. The correct method is to hone it down to make the balance shorter using a lathe or Jacob tool. 

[enz0]

6 minutes ago, clockboy said:

Reading through this post I would say at some time in its life it has had its balance staff changed and it is a tad to long.  As quick fix if the new staff is to long what is added is a thin shim under the balance cock or some create a notch in the plate., Both of these methods work but are a bodge. The correct method is to hone it down to make the balance shorter using a lathe or Jacob tool. 

Thanks for the response its really appreciated. I'm not quite there on my journey to attempt a proper fix with a lathe just yet however if I was to attempt making a notch on the plate how would you recommend doing it?

[Knebo]

1 hour ago, enz0 said:

Thanks for the response its really appreciated. I'm not quite there on my journey to attempt a proper fix with a lathe just yet however if I was to attempt making a notch on the plate how would you recommend doing it?

I'd suggest your first try a shim. Just to be 100% that the issue is solved by the height of the balance cock. You can use kitchen aluminium foil (single layer or folded one for a double layer). 

If then everything is fine, you can try the semi-permanent solution by making a notch with a screwdriver or a smoothing/cutting broach (with pointy tip). It doesn't need much at all. When you poke a hole, it naturally shifts to metal to create a bump. Take any spare movement plate/bridge to practice. Also see the video about from Mark, it takes him 2sec to poke the bridge with his screwdriver. 

[Neverenoughwatches]

2 hours ago, enz0 said:

Thanks for the response its really appreciated. I'm not quite there on my journey to attempt a proper fix with a lathe just yet however if I was to attempt making a notch on the plate how would you recommend doing it?

A shim would be a better idea, and will have a more permanent effect as the gouging marks can compress over time. The shim wouldn't deface the plate either, therefore a paper or foil shim can work well.

9 minutes ago, Knebo said:

I'd suggest your first try a shim. Just to be 100% that the issue is solved by the height of the balance cock. You can use kitchen aluminium foil (single layer or folded one for a double layer). 

If then everything is fine, you can try the semi-permanent solution by making a notch with a screwdriver or a smoothing/cutting broach (with pointy tip). It doesn't need much at all. When you poke a hole, it naturally shifts to metal to create a bump. Take any spare movement plate/bridge to practice. Also see the video about from Mark, it takes him 2sec to poke the bridge with his screwdriver. 

2 hours ago, enz0 said:

if I was to attempt making a notch on the plate how would you recommend doing it?

Bending the balance cock is also an accepted method, it may actually be bent down slightly. 

already

[enz0]

53 minutes ago, Knebo said:

I'd suggest your first try a shim. Just to be 100% that the issue is solved by the height of the balance cock. You can use kitchen aluminium foil (single layer or folded one for a double layer). 

If then everything is fine, you can try the semi-permanent solution by making a notch with a screwdriver or a smoothing/cutting broach (with pointy tip). It doesn't need much at all. When you poke a hole, it naturally shifts to metal to create a bump. Take any spare movement plate/bridge to practice. Also see the video about from Mark, it takes him 2sec to poke the bridge with his screwdriver. 

Thank you so much for the advice, I'll be sure to try it and hopefully that'll fix the problem

[watchweasol]

I would side with the shim idea as it does not deface the watch in any way. If at all later date you decide to change the staff/balance all is origional

[Knebo]

7 hours ago, Neverenoughwatches said:

shim would be a better idea, and will have a more permanent effect as the gouging marks can compress over time. The shim wouldn't deface the plate either, therefore a paper or foil shim can work well.

 

22 minutes ago, watchweasol said:

would side with the shim idea as it does not deface the watch in any way. If at all later date you decide to change the staff/balance all is origional

Ok, makes sense

[nevenbekriev]

Guys, OP actually says there is little end shake. Further more, the watch has been running somehow.

I would point attention to the hairspring. May be it is pressed to the balance spokes and lifting the cock (together with the spring) releases the balance.

Enzo, we need photos of the hairspring - from aside and from above, may be with balance over the cock