The central 20 bore has a "normal" parallel thread - that is that the centreline of the thread form is square (at 90 degrees to) to the axis of the bore. This device will rely on the thread form following a curved and not tapered, path from the outer (40) diameter to the centre 20 bore. A taper thread simply progressively varies in diameter along a taper, remaining at a constant angle to the workpiece, this thread has to vary in diameter along a curved path with the thread-form remaining square to the arc of the radius ( tangentially) and be of constant pitch. Any form of tap would simply produce a series of circular cuts on the curved face. Responses so far indicate that this is a rare and not readily understood bit of machining, and I am not aware of anything else out there that would require such a thread, I also am growing more hopeful that my device is indeed "new" and possibly patentable, so forgive me for not explaining fully, exept that the female thread discussed does not have a mating male part that fits to it, that last bit will no doubt cause a few more questions! Cheers, Mark G.
- posted
17 years ago