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WatchMaker

Balance staff help - OC 71 (OC 120; Rego 153?)

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Hi

I have a pin lever movement that needs fixing ... a common problem of a broken pivot on the balance staff. The movement has 'OC 71' on it but I have been unable to find any information about this particular movement. It does however looks similar to the OC 120 seen at http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&a&2uswk&OC_120 (which is a Rego 153).

Not being able to find any information on the OC route I sourced a balance complete for the Rego 153. This however is a dead end as the balance staff design is completely different. The picture below shows the issue.

2084077365_OC71.JPG.ff48420badcf8b7b0a55d077935963b7.JPG

The balance wheel on the left is the original where the balance roller can be separated. The balance staff from the Rego 153 balance complete is on the right; its design is completely different (and with the roller integrated into the balance wheel). Long story short there's no way it will work with the OC movement I have.

I am now stuck on what to do. With no information on the OC 71 how can I source an appropriate balance staff?  :blink:

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Hi
I have a pin lever movement that needs fixing ... a common problem of a broken pivot on the balance staff. The movement has 'OC 71' on it but I have been unable to find any information about this particular movement. It does however looks similar to the OC 120 seen at http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&a&2uswk&OC_120 (which is a Rego 153).
Not being able to find any information on the OC route I sourced a balance complete for the Rego 153. This however is a dead end as the balance staff design is completely different. The picture below shows the issue.
2084077365_OC71.JPG.ff48420badcf8b7b0a55d077935963b7.JPG
The balance wheel on the left is the original where the balance roller can be separated. The balance staff from the Rego 153 balance complete is on the right; its design is completely different (and with the roller integrated into the balance wheel). Long story short there's no way it will work with the OC movement I have.
I am now stuck on what to do. With no information on the OC 71 how can I source an appropriate balance staff?  :blink:

I could make one.


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Wow @Nucejoe and @jdrichard ... you are amazing!

This is a pretty basic pin lever movement and would normally go on the uneconomical-to-repair pile but I've gotten soft in my old age and would like to get it going. That's an incredibly generous offer @jdrichard but on such a basic movement it would be criminal to waste your talents; perhaps I keep this offer open for when I have something of greater horological value! <_<

@Nucejoe you've given me an idea that maybe I should get one of those job lot of staffs that come up on ebay and chance there is something to fit! On the off chance however that you can help identify a Ronda number with what I have then...

96966403_OC71balancestaff.JPG.5bac68d78183098ea20f97a2740ec696.JPG

A: current height is 3.90 however this is with the broken lower pivot. If I say around 0.20mm for a pivot length (reasonable?) then this would actually make the balance staff height around 4.10mm.

B: lower pivot to top of balance / collet seat is 2.10mm. Again allowing for 0.20mm for the missing pivot this would then actually be 2.30mm.

C: collet shoulder diameter is 0.7mm.

D: roller shoulder diameter is 0.6mm.

Dimensions are 'approximately accurate' i.e. taken as best I could with digital calipers!

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15 minutes ago, WatchMaker said:

Wow @Nucejoe and @jdrichard ... you are amazing!

This is a pretty basic pin lever movement and would normally go on the uneconomical-to-repair pile but I've gotten soft in my old age and would like to get it going. That's an incredibly generous offer @jdrichard but on such a basic movement it would be criminal to waste your talents; perhaps I keep this offer open for when I have something of greater horological value! <_<

@Nucejoe you've given me an idea that maybe I should get one of those job lot of staffs that come up on ebay and chance there is something to fit! On the off chance however that you can help identify a Ronda number with what I have then...

96966403_OC71balancestaff.JPG.5bac68d78183098ea20f97a2740ec696.JPG

A: current height is 3.90 however this is with the broken lower pivot. If I say around 0.20mm for a pivot length (reasonable?) then this would actually make the balance staff height around 4.10mm.

B: lower pivot to top of balance / collet seat is 2.10mm. Again allowing for 0.20mm for the missing pivot this would then actually be 2.30mm.

C: collet shoulder diameter is 0.7mm.

D: roller shoulder diameter is 0.6mm.

Dimensions are 'approximately accurate' i.e. taken as best I could with digital calipers!

According to balancestaffs.com, The closest would be rego 148, correct you are153, 154, 148, 1149 linge 13.5 .

I forwarded the pic you posted to this retired repairman  just by the looks he says he got the staff but not the impulse pin and added looks like you can use an impulse pin, looks damaged.

To get the exact right staff, we now need a friend with micrometer.   I,ll dig in my bag of tricks for possible complete balance, don,t even know if spare ones were marketed.

Next I,ll check your birthday date.

Regards

 

 

 

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Thanks @Nucejoe that's very useful and with that information I've looked at balancestaffs.com. The problem with the Rego 148 I see is that the staff design does not look quite right plus the shoulder widths are too large.

You are quite correct ... the original staff had a balance roller that slides onto the staff. I removed this (and it's shown in my original pic) and would be the part that slides onto the 0.6mm roller shoulder.

But your mention of balancestaffs.com gave me an idea for a reverse look up attempt. They measure to the 100th of a mm and because my staff height measurement is an approximation I played with look ups for heights from 4.05 (405) to 4.15 (415). From this I came across a possible fit for a balance staff with Ronda number 1912. Okay this is for a Waltham but dimensions for the crucial areas come up close to my measurements. Mmm ... could be worth a punt maybe.

 

Edited by WatchMaker

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1 hour ago, WatchMaker said:

Thanks @Nucejoe that's very useful and with that information I've looked at balancestaffs.com. The problem with the Rego 148 I see is that the staff design does not look quite right plus the shoulder widths are too large.

You are quite correct ... the original staff had a balance roller that slides onto the staff. I removed this (and it's shown in my original pic) and would be the part that slides onto the 0.6mm roller shoulder.

But your mention of balancestaffs.com gave me an idea for a reverse look up attempt. They measure to the 100th of a mm and because my staff height measurement is an approximation I played with look ups for heights from 4.05 (405) to 4.15 (415). From this I came across a possible fit for a balance staff with Ronda number 1912. Okay this is for a Waltham but dimensions for the crucial areas come up close to my measurements. Mmm ... could be worth a punt maybe.

 

Normally anyone who used to work on a certain caliber, should have bunch of scrap balances, from which a good impulse pin can be removed and reused. I don,t see that as anything unusual, The problem  is proper removal and installation which requires staking set and some skill, So as long as you got a good HS and the matching wheel , the rest is what used to be routinely done at repairshops. Another wheel is not a good option. Hardly any demand for parts to such old pieces so they are cheap.Once we know the right one, I think I should send two just to be on the safe side. I guess many diferent size staffs of similare shape we made for various calibers. 

I got a feeling this is one of those instances you see an old piece which gives a feeling of the golden days and you feel good bringing it back to life. I enjoy seeing you see the job through for that feeling and is truely worth it.  

I had no idea I could get this poetic.:lol:      regards

 

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:biggrin: As the saying goes:

You're a poet ... and you didn't know it!

It"s just the staff that is shot so I'll take a punt on the Waltham close match. I usually work on jewelled movements that are more commonplace so parts, even if pricey, can at least be obtained. Pure lack of information on OC calibres was the main enemy here but I have the tools and patience to at least give the Waltham close match staff a go! 

Perhaps recentlly reading the book Longitude has made me persevere on this pin lever. People struggled for many decades to get a device to measure time accurately and here we have the very essence of simplicity to do that in something very humble. The rose tinted specs come off with the lack of any shock protection though ... :rolleyes:

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