D'oh, fitted wrong balance hole jewel. Is there anywhere to look up balance staff pivot sizes ?

[mikepilk]

Having swapped the lower balance hole jewel on a Movado 150MN, I realise the hole is too small 

Not having a pivot gauge, I use a micrometer - I know it's dangerous! . So rather than close the jaws on the pivot, I set say 0.09mm, and gently lower the pivot to see if it fits.

I must have made a mistake, as I've re-measured at about 0.095mm*. Which seems an odd number.  Do I need a 0.10 mm or 0.11 mm hole?

There's plenty of sites showing balance staff sizes, but I haven't found any listing pivot size. Anyone know how I can determine it ?

* I wonder about the accuracy of my micrometer as the 0.09 mm hole jewels I bought will slide over the pivot, though they are a snug fit

Edited August 8, 2023 by mikepilk

[nickelsilver]

I don't know any source of info for pivot sizes, with the exception of some old info on American stuff. If the jewel fits, but doesn't want to tilt at all*, I would go to a 0.10mm hole. Manufacturers did indeed use half and even quarter sizes (0.095mm for example) for jewels, but in a case like this going up to 0.10mm with a 0.09mm fitting "snug" should be just right.

 

*With a proper balance jewel, the hole will be olive shape, and even if very close in size should allow a surprising amount of tilt.

[Neverenoughwatches]

3 hours ago, mikepilk said:

Having swapped the lower balance hole jewel on a Movado 150MN, I realise the hole is too small 

Not having a pivot gauge, I use a micrometer - I know it's dangerous! . So rather than close the jaws on the pivot, I set say 0.09mm, and gently lower the pivot to see if it fits.

I must have made a mistake, as I've re-measured at about 0.095mm*. Which seems an odd number.  Do I need a 0.10 mm or 0.11 mm hole?

There's plenty of sites showing balance staff sizes, but I haven't found any listing pivot size. Anyone know how I can determine it ?

* I wonder about the accuracy of my micrometer as the 0.09 mm hole jewels I bought will slide over the pivot, though they are a snug fit

Jacot time ? Is the reason pivot sizes aren't listed because they are easily adjusted ?

[mikepilk]

4 minutes ago, Neverenoughwatches said:

Jacot time ? Is the reason pivot sizes aren't listed because they are easily adjusted ?

I don't want to mess with the pivots - I just fitted a new balance staff ! 

I just messed up measuring the pivot sizes when I ordered the hole jewel. 
I've broken pivots before when measuring with a micrometer, so I was very cautious, and obviously got it wrong.
What I should have done: I have some spare 0.09mm Incabloc hole jewels. I could have sat one on the pivot to see how it fit.

It is odd though, that all the dimensions of balance staffs are shown apart from the pivot size.