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jdrichard

Transplanting a Pinion

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I am replacing the hour gear on an old Large Swiss Pocket Watch. The old pinion had 12 leaves and X teeth and the gear I found has 10 leaves and less teeth on the wheel. When I dropped in the gear and then the center hour gear, I turned the crown and everything seems to work and the gears are meshing properly and the minute and hour hands are coordinated (didn’t think that was possible. Now it still feels a little tight in places when I set the time, so I have decided to transplant the pinion to another gear that has the same size and teeth count as the original; plus the original pinion is thicker.16e9331da8e361df3d714f1ecfc9d1f4.jpg735a6a3077676f04028c77411015d183.jpg

So what I am looking for is advice on transplanting the old pinion to the new gear.c48fca3f341ff1c78f637f4795fd1e77.jpg

 

 

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I'm counting 12 on both pinions there. Maybe start by sleeving the bore of the new pinion, it looks much bigger than the old one. That will allow it either engage more deeply or shallowly depending which way you're turning it.

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The pinion I actually used is the one in the movement picture and not the one in the double pinion picture. However the one I used has the 10 leaves. It sort of works. The two pinions I the other pic are the transplant candidates. Just not completely sure how to transplant a pinion.

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First thing would be to remove the pinions. They are sometimes quite well rivetted, so this may involve turning away some of the rivet or being willing to sacrifice the wheel (it could easily be distorted beyond use in punching the pinion out). Then you need to compare the hole in the wheel you want to use to the diameter on the pinion that will be pressed and rivetted in. If too big it gets tricky, you'll need to sleeve/bush the hole very securely. I would open the hole further, then chamfer both sides, make the bush with an undersized hole, then fit it in. Swage the bush with a convex punch in the hole from both sides, then a flat punch that is larger than the bush. The idea is to deform metal into the two chamfers on the wheel. Finally flatten and clean up. Now open the hole to receive the pinion.

If the hole is too small it's easy, just open it up and press/rivett the pinion in.

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