I am trying to purchase a set of taps for pocket watch cases typically size 16 and size 18. I want to be able to chase out the threads in certain instances or possibly re-tap the pendant so it will fit the sleeves that I already have. Does anyone know where I can purchase the various taps that will allow me to tap out the pendants on antique pocket watch cases? I have a lot of size 16 and size 18 cases and the sleeve has been rusted in there and I destroy it getting it out. I need to be able to tap that hole. They are extremely fine threads and I would definitely need a bottoming tap to do it correctly. The picture I am including shows one with the stem and sleeve frozen in the pendant. I would really like a book that explains all of the different styles of sleeves and stems and crowns that are used in hunter cases and old size 18 cases and mainliner cases that have a cap on them. Please help I think I have found a niche in the market if I can learn to work on just antique pocket watch cases especially railroad grade. Again, please help
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Unfortunately, I know of no taps that are available for tapping a pendent that will match typical sleeves. In addition, retapping a pendent would require a larger full depth thread and in many cases you are unlikely to have enough wall thickness to support a larger thread. A better solution may be to rethread a very close sleeve with a die. More on that later.
Again the issue of finding Taps and dies. I measured a sample 18s and it was a .201" x 60 TPI that would be extremely unlikely to find even on your luckiest day. But even if you were to find one, it may not be what you are looking for just to chase and clean a thread, since it is likely to remove metal. For oddball threads that need to be cleaned and reformed slightly without removing metal, I make a special tap as follows.
(1) The tap is machined from Drill rod per the first attached photo.
(2) The nose (red arrow) is rounded allowing the thread to start. The body (white Arrow) will be threaded. The relieved area (green Arrow) will supply spring tension.
(3) A slot is machined to supply both a cutting/cleaning tooth edge and spring tension on the thread when hardened/tempered. the slot should be ever so slightly expanded on the end to provide thread tension after threading but before hardening/tempering.
(4) The second photo shows single point cutting whatever thread is desired or required. A drill bit shank was inserted in the slot to support the two half`s while threading. Threading should only be done after the slot is cut to provide sharp edges on the thread teeth.
A die can also be machined once you have machined a standard Tap.
I have covered machining, hardening and tempering micro taps and dies in detail, in a article published in the 2008 Jan.- Feb. of the " Home Shop machinist". For anyone interested, they will send a reprint of the article by phone call. 800-447-7367
Its more than is practical to cover here.
While a little time consuming in the beginning, you eventual accumulate what you need as well as a very useful skill.
Jerry Kieffer