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Buffo

Shaping a ruby pallet stone

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I suspect that you're going to need some kind of a diamond lap to do that. 

It's not something I've ever tried to do but I would imagine your going to need a jig of some kind to hold everything true, and then successive finer laps to first remove material and then polish the surface. 

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I'm not sure how the OP thinks he can do this, but if with the stone in the fork, assuming it would be even possible, then the stone will become too short and not have the right lock and draw.
Faulty stones should be replaced.

 

 

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Thanks for the responses.

I realize that diamond is probably the best option, but I have managed to shape and polish corundum in the past without resorting to diamond polishing compounds.

I would not attempt to do any shaping with the stone mounted in the fork. I was thinking more of dopping a stone (I've got a small selection to choose from) on to a stick (tooth pick) and gently working it to the proper length and angle.

The movement I'm having a go at is a 1923 Elgin 16s, 7 jewel 292 cal. The escape wheel is in good condition, but one of the pallet stones on the fork is "cactus." As a last resort I can splurge on a new complete pallet with stones from Cas-KerCoy, but $50 USD is a bit much for this Aussie. Besides I kind of like the idea of seeing if I can get this thing ticking again with what I have at hand.

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In theory you can work ruby with anything harder or as hard (diamond is worked with diamond), but it's so easy and cheap to get diamond lapping compounds and powders that it's really the way to go. I'd suggest a copper lap rotated in the lathe, but almost any material is ok- acrylic, iron, etc. For pallet faces I would use 1micron diamond, it will cut slowly but surely and leave an entirely satisfactory finish.

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jdm and nickelsilver, thanks for the URL and the excellent suggestions on laps and lapping compounds.

I have ordered a selection of stones that is suppose to contain pocket watch size specimens from another supplier. As it might be possible to find a suitable pallet stone in a random selection, I do believe that shaping and adjustment will still be necessary, hence  my question about lapping compounds.

I value the responses of all who replied and thank you for your excellent suggestions. I'll try to let you know if I have any success at this endeavour.

Buffo

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Just now, Buffo said:

jdm and nickelsilver, thanks for the URL and the excellent suggestions on laps and lapping compounds.

I have ordered a selection of stones that is suppose to contain pocket watch size specimens from another supplier. As it might be possible to find a suitable pallet stone in a random selection, I do believe that shaping and adjustment will still be necessary, hence  my question about lapping compounds.

I value the responses of all who replied and thank you for your excellent suggestions. I'll try to let you know if I have any success at this endeavour.

Buffo

Generally speaking you can replace a pallet stone with another of the same width, and that has been shaped for the appropriate side of the fork (entry or exit). Let's say for your average vintage watch, a replacement stone from Seitz or other assortment will probably be just fine. You do run into issues with certain escapements for higher end watches from back in the day or modern watches with higher beats and more teeth in the escape wheel; often older high end escapements might have significantly different face angles from "common", and modern escapements have very different angles for sure. Usually it's possible and normal to replace an entire fork for a modern watch. With vintage/antique it can be very advantageous to fine tune the angle on the impulse face.

One issue with replacement stones is that they are sometimes just too long overall, and need to be shortened. This is usually done on the end that fits in the fork as it just needs to be approximately squared off; I do it with a fine diamond grinding wheel (7 micron) holding the stone in a tiny vice. I suppose it could be done with a fine diamond file, but these will tend to chip the stone and while not affecting the function it is unsightly.

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