Broken Jewel

[adiorio110]

Hi

I have an Elgin 16s with a cracked jewel where the pallet fork rides. Is there a specific name, size for this. I am not sure what I should be searching for.

 

Thank You

Anthony 

[StuartBaker104]

It's a pallet staff jewel and it's unlikely you will be able to buy this by name, you will have to take it out and measure it then scour the globe for one. Good luck with that bit. Some say it is more sensible to take one from a scrap movement, but finding one of those can also be hard.

Search this forum for "rubbed in jewel" and you will get a few hits which will explain.

Szbolagh will no doubt be along shortly to show you how to grind down a more readily available pressed in jewel into the right shape!

[jguitron]

Hi

I have an Elgin 16s with a cracked jewel where the pallet fork rides. Is there a specific name, size for this. I am not sure what I should be searching for.

 

Thank You

Anthony 

You're right, it has to be replaced. It appears to be a friction jewel which means it's only held in place by the pressures of the walls around it. Typically 0.01mm bigger than the whole.

Before doing anything to it you should measure the depth it was from the level of the main plate. How deep or shallow determines the endshake and so it is helpful to know it before you push the jewel out. Once out you have to measure the size of the pivot hole unless you have a gauge that has like 80 sizes where you put your pallet fork or wheel until you find the right size. This is very important as it determines the sideshake.

Anyway, once the jewel is out you have to find its replacement based on your measurements. Jewels don't have specific positions, just sizes. There are Seitz sets with hundreds of vials that contain all sorts of options out of which you pick the best possible match.

Then the fun part is to use your jeweling tool to gently tap the jewel into position, i.e. Friction fit it. Using the depth measure you got before removing the old jewel you tap the new one in. Like i said, it's ideally 0.01mm bigger than the whole. Too big and it will crack as you try to force it in. Too small and it won't stay in place.

Once you get it where you think it's right you should test it by assembling the balance wheel and fork to check endshake and look at interaction with balance wheel. If it's good then move on to assembling the train so you can check interactions with escape wheel.

This is fascinating stuff that I wish I had more experience in but this looks like a great case to start for you if you have the tools and interest.

Good luck!


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[szbalogh]

31 minutes ago, jguitron said:

Then the fun part is to use your jeweling tool to gently tap the jewel into position, i.e. Friction fit it. Using the depth measure you got before removing the old jewel you tap the new one in. Like i said, it's ideally 0.01mm bigger than the whole. Too big and it will crack as you try to force it in. Too small and it won't stay in place.
Good luck!

 

 

It is a rubbed jewel setting. No need for a perfect outer diameter match.