Replacing a rub-in jewel hole

The balance on this vintage pocket watch movement has a rather large amount of side shake and low amount of amplitude and upon investigation I found that the jewel hole on the balance cock is damaged. This is a rub-in style of jewel and a new one will need to be fitted using specialist tools for the purpose.

I start by removing the balance assembly from the cock by unscrewing the stud screw. This loosens the stud from the balance cock and allows me to push the stud out.

With the balance assembly removed from the cock I now have access to the end-stone screws. After removing these screws the end-stone falls away alone with the regulator index.

Now I can properly inspect the jewel hole and indeed it is quite damaged.

First I will extract the old jewel, and I do this with a jeweling tool. This one is made by Favorite although Seitz is another popular brand. After choosing a pusher of diameter slightly smaller than the jewel and set the vernier gauge so that the pusher rests just above the jewel I press down on the tool handle whilst slowly turning the vernier adjustment which causes the pusher to press down on the jewel. Doing this slowly allows the jewel to be extracted whilst the metal holding the jewel in place opens but doesn’t split.

After removing the old jewel the metal surrounding the jewel is still fairly compressed so we need to use the spreading tool to open the diameter enough for the new jewel to be seated.

Now I need to use these kinds of jeweling tool specially made for rub-in jewels. In this set there are two tools of several sizes each. One is to spread the metal which holds the jewel in place so that the new jewel can be placed. And the other is to close the metal around the jewel once fitted thus securing it tightly in place.

I’m applying some oil to the tool jaws then after inserting the jaws into the jewel seating I adjust the screw so that the jaws speed outwards and arrest the metal. Then I turn the tool and continue to open the jaws until the gap is big enough for the jewel to fit.

Next I place the jewel into the cavity and using the jewel press I drive the jewel down into its seating, and this ensures that the jewel is flat to the bottom.

Now its time to rub the metal over the jewel so as to secure it.

First I apply some oil to the metal and after adjusting the concave rub over tool to the correct diameter I apply some downwards pressure whilst turning the tool slightly adjusting the diameter if needed. Inspecting the jewel and seating I can see that the metal is now holding the jewel in place with no gaps or wobbles. Its time to re-assemble the balance

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