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.
Re tricky thread
Nov 26, 2006
8 Replies
Mill and then cut yourself a tap??
So it's purely decorative then?
You do realise that as you tap away on your keyboard someone in China is at this precise moment drafting a worldwide patent on methods to produce such a thread so you'll never be able to make it without paying them a huge royalty payment on everything you make :)
I'd hazard a guess that it's something that's designed to engage with the end of a normal male thread from a wide angle, without the parts needing to be perfectly parallel. But it'll still cross thread.
Having looked at Peter's Quimby pump it sounds more like another pump!
Henry
I really want to know what this thing is for, apart from getting a finger stuck in :)
Sounds like you require a square-form thread, but would a round-bottomed thread do? One cut with a tool something like that below - a rounded cutting tip on a slender neck:
,--,_____ ( __ \ '--' \ \ | | | | : :
This would do away with the need for adjusting the tool angle to be tangential to the inner surface, so could be done on an ordinary cnc lathe.. hopefully.
cheers Guy
Mark, drop me an email off-list (my email address is real). I think you're going about this the wrong way.
Regards Kevin
If you free off the toolchanger to allow it to rotate and control th rotation with a cam pattern fixed to the bed or mounted from th tailstock, would you get enough stability?
Just a variation really on a taper turning attachment controlling too angle rather than the slid
-- rss
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