Not one to boast, but I finished a repair today, that was a challenge. A Ball Watch Co. grade 435C pocket watch (made by the Record Watch Co. of Switzerland) came to me recently, for repair. It was rough! Missing crystal and minute hand, broken escape wheel pivot (conical), rust, broken mainspring, etc. My first challenge was to deal with the broken escape wheel pivot. Many phone calls and emails resulted in no luck trying to locate a replacement wheel. So I would have to repair the broken pivot. The stump for the broken pivot is 0.40 mm in diameter, so drilling was out of the question. The solution was to fabricate a pivot cap. I drilled a ferrule to fit over the broken stump, and shortened the broken stump by about .80 mm. I made a steel “plug” for the outer end of the ferrule. Pivot size 0.07 mm, hub size 0.40, length 1.2 mm. Inserted the plug into the open end of the ferrule, and shellacked it all into place. Running beautifully with the completed repair. This will do until a replacement wheel shows up (unlikely). The watch is not worth the effort it took, but you can’t disappoint a friend.
I don’t have before pictures, and I am not about to dismantle it to take pictures of the repair. Sorry. But here is a sketch of the repaired pivot, and pictures of the watch, running. It is NOT a pristine example. It came to me badly rusted, and i’d Have loved to have the budget, and the parts source, to restore this old pelter.
Interesting method. Reminds me of those pivot caps you could buy that they made for balance staffs way back when... Did you consider just machining off the entire "stump" as you call it and just making a new one with the pivot already on it, that could be fitted into the pinion? That's probably the way I would have done this one, but if this works you can't complain I guess.
I’d contemplated this repair for weeks before I chose my method. To drill the pinion, I would have needed a 0.40mm drill, since that is the diameter of the arbor. Probably carbide, considering drilling the pinion. Break a carbide drill off in the pinion? I had already given up trying to replace the wheel, so I felt the method I used would (hopefully) result in a useable wheel. The “plugs” I made were very tiny. I lost two, and broke the 0.07mm pivot off of the third one. The 4th one worked a charm. Watch runs beautifully.
Well it worked, so you can't complain, and I understand the fear of a broken drill. What material was the ferrule made from?
I used brass for the ferrule. Might have tried steel, but I was looking for a short cut, since I undertook the repair of this sadly deteriorated watch for a friend, for not a lot of money. In retrospect, I probably should have turned him down! I was astonished at the tiny diameter of the escape wheel pivots.