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Enlarge pocket watch roller hole ?

Chopin

By Chopin
in Watch Repairs Help & Advice

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Chopin Super WRT Addict

Chopin

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I have a pocket watch that required a balance staff replacement. I've bought a NOS original one. The length fits, I even mounted it onto the balance and then onto the movement and everything checked out.

Upon trying to fit the roller I realized that it wouldn't fit. From research they made 2 versions of either balances or balance staffs or I don't know what exactly but the bottom line is that all parts are genuine, it's just that I have the roller or staff from one version and the rest from the other version (the hairspring collet also fits so only the roller hole is the issue).

You can't really find these parts and I don't want to invest anymore so I was wondering if it would be possible to simply enlarge the roller hole.

I don't have a lathe but I have ordered some mini-drills that come in all sorts of useful sizes. I would have to enlarge the hole by about 0.8mm.

It would have been helpful if I could find a really thin file to do this or maybe use some sort of a wire that behaves like a file but I doubt it.

Thoughts ? Suggestions ?

The pocket watch isn't an expensive or special one by the way so that's why I'd like to give it a go rather than invest a lot of money.

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wls1971 Distinguished Member

wls1971

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6 minutes ago, Chopin said:

Oh this is exactly what I'm looking for, I think.

Are these basically "needles" with a texture similar to that of a file ? I can't find a close-up shot.

No broaches are five sided each side is a cutting face you insert and twist and the faces cut as you do so, they must be used at a perfect 90 degree angle to cut a perfectly centred hole, similar broaches are used in jewelling tools to enlarge jewel holes, the German ones that Cousins sell are cheaper than Bergeon and are very good the Indian ones I would give a wide berth. 

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jdm Distinguished Member

jdm

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1 hour ago, oldhippy said:

Perhaps I should have said watch movement holder. 

Chopin was asking about a way to hold a balance roller. Can't use a mov.t holder for that. 

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Chopin Super WRT Addict

Chopin

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The roller is very small. These holders have too large gaps to actually hold the roller.

I could use a normal vise (I have a small one) but it's hard to keep a round disk in place with a vise especially since, if at some point the roller moves or jumps out of the vise jaws I might damage it or break the roller jewel itself.

I'll figure something out I guess. Was thinking of making a hole in a cork screw or maybe a piece of wood (this one might be a bit more complicated...) but it still wouldn't really hold the roller in place if I want to drill the hole.

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nickelsilver Distinguished Member

nickelsilver

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Opening a roller by 0.80mm is a lot, and it looks like a steel roller so going will be tough with a broach. Possible you don’t have the wall thickness to take that out even provided you have a good way to hold the roller and some buttkickin broaches. Best would be to turn down the staff.

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