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Longines Balance staff pivots - are they too flat ?

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6 minutes ago, Klassiker said:

Aww! I thought I was going to get a game-changing super-secret hot tip. Couldn't you make something up just to stop me being so disappointed?

I have used pink rubber erasers to clean battery contacts, as they are slightly abrasive. I have even used them to touch up the grained finish on some movement parts that were marked or stained- but that's hit-or-miss.

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    • by the way this is very confusing to me? You have a 7s26a and you're comparing it to a 7s26b which is confusing to me because they're not the same? Watch companies are rather amusing when it comes the part numbers seemingly watches with similar  numbers as you're implying should be exactly identical but in this case they are very very dramatically different for instance the 7s26a balance part number is 0310 020 the 7s26b has a different part number 0310 197 as the part numbers are entirely different there must be a reason it noticed that I made two terms in the quote above in bold regulator pins are versus the etachron  system. In addition to changing the regulation part more than likely they change the hairspring. So this would typically main you wouldn't build a swap balance completes from one type to the other because they will be entirely different. this is where looking at the technical guide might yield some amusing information. you'll note in the 7s26b  service guide it explains what the difference is. It makes a reference to the balance staff which is totally inconsequential for this discussion. But the really big difference is the A  version has conventional regulator pins and the B  has is the Etachron  system. In @Jon excellent images up above he didn't explain something? if you look carefully at the images below you'll notice that the outer terminal curve is different  as a guest to accommodate the etachron  system it looks like the terminal curve is farther out. So yes exactly as the parts list indicates the balance completes will look different because they are different. Because they are different there are not interchangeable. so basically because the letter changes at the end in this particular case we end up with two separate balance completes as proven by the parts numbers. Balance completes that are entirely different to accommodate the regulation system conceivably with entirely different characteristics of timing as they are entirely different. So your observation of the balances are different shape is correct they are different.      
    • See, the problem with widening to a little bit wider diam is that the bit will 'grab' too much at a time and will get in too fast by itself, then it will stuck and break imediatey. If enlargening from 0.3 to 0.5 needed, complitelly different drill bit must be made - it must be similar to the ones they use for weapon cannons, with one cutting edge and with angle that will not cut fast. The other option is to enlarge the hole like they do on big lathes with cutter for internal turning, that will be small enough to get in the hole
    • Thanks for all the comments. I think I'll go back to restoring BMW motorcycles and making model steam engines.  Dave
    • Yep my thoughts the same,  i realised i slipped up with the smaller drill half way through. Out of curiosity if you had to widen a hole, could it be plugged and re- drilled ? 
    • I think that if this is a spring wire like piano string or similar, it will not break and  wili be srong enough. What You could do is to drill straight with 0.5 . Then it would be beter, but now it is good enough to do it with 0.3. See, the watchmaking is actually a piece of cake, just some practice and skills to develope needed and to believe in own strenghts
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