Watch case engraving fixture/mandrel

In addition to engraving my interests include but are not limited to, vintage double barrel English shotguns and the repair, rebuilding and restoration of fine vintage mechanical watches. Therefore a couple of weeks back I decided that I would tackle watch case engraving, and that first I would design and build a fixture to hold watch cases in all the angles that are needed for engraving them, including the watch case back.

The watch case fixture/mandrel is designed on the basis of an expanding collet, versus the standard machinist collet which collapses when used. The expanding mandrel/collet is designed to use machined rings for the various size watch cases. For example the larger watch case in the photos has 28mm, 28.50mm and 29mm internal diameters and I made a ring to fit over the mandrel/collet to those measurements.

As you will determine the the mandrel collet is tightened via set screws holding the watch case securely from the inside--not outside.

I have posted enough photos of this fixture that should allow you to build one for yourself, or to have someone with a metal lathe to build one for you.

Steve

Fantastic idea! Also, one of necessity when doing the outside of the case. Better, I feel, than thermoloc, and, no risk of heat damage or crystal failure. Nothing wrong with some gadgets & helpers to keep from screwing up a guy's, or gal's, watch.

Very ingenious and versatile design. I can envision many uses in machining for an expanding collet like this when machining the exterior of a closed end cylinder. Thanks for posting and sharing it.
Cheers
Don

yeah, that's a way cool invention.