What do those screws regulate on Rolex 3130 movements?

[BennyE]

I watched Marks videos many times, but I can‘t recall that those screws (picture below) were ever discussed. Looking at them, they would control how high the overall balance bridge sits and therefore would allow to fine-tune the end-shake, or am I missing something else?

Thanks,

Regards,

Benny

[oldhippy]

You are correct. 

[BennyE]

Thank you, so all those hours on the available videos were worth something.

Have a good remainder of the day and an amazing weekend!

Benny

[Nucejoe]

That,s what they are for and I guess its loyalty belongs to Rolex since havn,t seen em  like this on any other brand, only a similar idea , a scerw right on top of the cock jewel to directly  regulates its end shakes, mainly on old watches. 

[BennyE]

Simple idea with a big impact

[anilv]

Better than foil shims or (heaven forbid) gouges on the mainplate!

Anilv

[VWatchie]

51 minutes ago, anilv said:

Better than foil shims or (heaven forbid) gouges on the mainplate!

Anilv

We see a lot of foil shims on Vostok movements (cal. 24xx). It's an extra step when handling the balance cock, but besides that, what is it that makes you oppose them? I often wondered why they are needed. Of course, to regulate end-shake, but besides that. Perhaps lack of precision in manufacturing, no? Note that I'm not looking to dispute you, I'm simply curious and want to learn more. Thanks! 

[AndyHull]

1 hour ago, VWatchie said:

I often wondered why they are needed.

I often wonder about that too. Surely if the manufacturing process was well controlled, then there would be no need for them.

Perhaps their original intention was to allow for thinner and thinner shims at each service, as the pivot ends wear, but that is just speculation on my part.

What I do know is that they represent one more thing for me to ping into a parallel dimension, or simply forget to refit, risking damaging the jewels and pivots in the process, so perhaps they are simply intended as a trap for the uninitiated.

[Tmuir]

Or is it simply they use the balance cock on more than one caliber and the shim lets them do this?

Edited August 23, 2019 by Tmuir

[AndyHull]

That's good shout. I suspect they may have had multiple sources for the balance, and thus the shim was fitted in some cases, to allow them to compensate for the 0.1mm or so difference between shaft lengths.

The shim can be source of problems though as it can act as a pivot point if it is not fitted in entirely the right spot, and this could introduce errors in the balance alignment, and it does introduce the possibility of either forgetting to re-fit it, and screwing the balance down hard on to the jewels, thus damaging the pivot(s) and/or the jewel(s), or fitting it when not needed if a different "compatible" replacement balance is fitted which has a shorter shaft, and then getting in to head scratching mode when the thing rattles around like a pea in a biscuit barrel.

Edited August 23, 2019 by AndyHull

[jdm]

7 minutes ago, AndyHull said:

That's good shout. I suspect they may have had multiple sources for the balance, and thus the shim was fitted in some cases, to allow them to compensate for the 0.1mm or so difference between shaft lengths.

No need for having multiple sources to suffer parts size variations. Parts are made in batches afterwhich the same machine is reconfigured for another part or another step on the same batch. True in the old times of mechanical stops as well as in CNC of today. An error during reconfig, a larger tool wear there, temperature variations and you may be making parts significantly different. Very old watches were made practically by hand so to fit each part to another. Russians probably had decent machines but onerous production targets, impossible to impose strict tolerances so if the problem was correctable at assembly, so be it. 

[AndyHull]

That makes sense. The watchmaking equivalent of the bodge wire in electronics.

[DavidMasters]

5 hours ago, anilv said:

Better than foil shims or (heaven forbid) gouges on the mainplate!

Anilv

Gouges are a method that has always made me shudder when I see it.

Regards.

[anilv]

WRT shims.

VWatchie..I've always thought that shims were a band-aid solution and a manufacturer should have the capability to reduce the length to spec in-house. Probably as JDM mentioned it could be due to production variance. Better to have it slightly too long than too short?

One thought is that they could have done that (shims) to build some life into the movement.. ie you could re-finish the ends of the pivot sometime in the watches lifetime and at that point doing away with the shim (or use a thinner shim) leaving you with good endshake?

Ah well... unless someone who has worked in a Soviet watch factory shows up we'll probably never know.

Anilv