Shaping a ruby pallet stone

[Buffo]

G'Day,

Anybody know of a fine wet/dry paper or stone that one can use to shape the impulse face of a pocket watch (16s) pallet jewel?

Any help appreciated.

Buffo, FNQ,Au

[Marc]

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. 

[clockboy]

I doubt it the only material that might work is something like a diamond lap. There is a vid on the net showing someone grinding a jewel on a lathe with diamond paste. 

[jdm]

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.

 

 

[Buffo]

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.

[jdm]

What about this https://www.cousinsuk.com/product/pallet-stones

It says for wristwatch, but you never know. 

[nickelsilver]

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.

[Buffo]

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

[nickelsilver]

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.

[Buffo]

nickelsilver,

Thanks for that. This is just the sort of information and encouragement I need for this project.

Buffo

[VWatchie]

On 12/9/2019 at 2:51 PM, nickelsilver said:

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’m reading the chapter “Replacing a Pallet Jewel” in Henry B. Fried’s book “The Watch Repairer’s Manual, Second Edition”. On page 204, he suggests how to shorten a pallet jewel and I quote:

“Should a jewel be chosen with all dimensions correct except that it’s too long, it may be shortened to an acceptable length. This is done by drilling a fine hole into the end of a piece of pegwood and placing the jewel, lift surface (impulse face) inside, so that the excess length is the only part protruding from the pegwood. The jewel is shellacked into place, and the protruding end is held against a diamond-charged lap or wheel…”, etc.

So, this seems like a nifty but somewhat cumbersome method, especially when compared to your suggestion of using a "tiny vice". Furthermore, I can’t figure out is how to shellack the jewel into place in the piece of pegwood, and the chapter doesn’t explain or suggest how it can be done.

So, I'd rather use a tiny vice like the one you mention if one can be had. Can you perhaps tell me a bit more about the tiny vice you use (the shape/material of the jaws gripping the jewel), and perhaps suggest where one can be obtained?

I don't have a diamond grinding wheel or the machinery for such a wheel, but was hoping perhaps I could use my 3M lapping film. However, as you mention: "In theory you can work ruby with anything harder or as hard (diamond is worked with diamond)" so maybe it isn't such a great idea? Any alternative suggestion for the budget of an amateur repairer? I do have a 1200 grit diamond stone which I use to dress my screwdriver blades, but I'm thinking it's likely too coarse and would make the jewel look, as you put it, "unsightly", or what do you think?

Edited December 14, 2020 by VWatchie

[nickelsilver]

The little vice I use is made by Horia. It's not cheap but very excellent. Mine is 21 years old and gets used several times a day, every day. I have seen similar/copies in catalogs since I bought mine for about half the price, but can't remember where now. It's a typical tool young watchmakers might make in school (if they have free time) as it's a good exercise and very worth the effort- but you would need a milling machine to make one.

 

https://www.horia.ch/en/Products/Tools/Tools/Vice.html

 

For diamond abrasives on a budget Eternal Tools is hard to beat. I can't remember if you have a lathe or not, if so you can buy cheap diamond paste from numerous suppliers and use it on a lap as I wrote above. You will want a separate lap for each grit, the whole idea is it embeds into the lap- there's no cleaning it off. Eternal has diamond wheels and round laps down to D9 or 2000 grit, which would be fine for shortening a stone. You need finer, at least 3 micron to work the functional surfaces.

 

https://www.eternaltools.com/

Edited December 14, 2020 by nickelsilver