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Acme Tap

Alexander

Alexander

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Im working on my manual lathe and im wondering if anyone has a 7/8 or 3/4 acme tap. I just want to tap one hole in a piece of aluminum. Hoping soneone has a 7/8 - 6 acme tap right hand.
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thanks
 
I have a nut already and I could use it. The nut is not really designed for transmitting motion and would have a few drawbacks. The material is mild steel so it is not ideal and the length of the thread is somewhat short.I think I could probably cut the thread to half depth and make a stub acme thread on my CNC lathe. I talked to a manufacturing professional who thought trying to cut a full acme thread with a tiny boring bar sounded like a waste of time.The problem is the bar needs to fit in the .660 hole and make it to .105 straight depth. That will take some doing and rigidity of the cutting tool will be an issue. Those taps are the best deal i have seen so far and I somehow missed them when i was searching online. My preferred local source for tooling quoted me $258 for a tap that only cost 150 on that list. im still working on this. My main problem is how much the tooling will cost if i just buy the right tool for the job.
 
Can a tap be made at home? Seems similar to the gear teeth cutters some people make. Just musing out loud, cut a taper on lathe, cut discs into the taper on lathe, then mill slots transverse across discs to make teeth. Sharpen the teeth. Use O1 or something as the stock, maybe drill rod, and then heat and harden. lots of fussy work... but cheap? practical? Josh has a kiln with a temp read out for the heating.
 
I do have some acme nuts but as stated, they would be too soft to thread with unless it was soft material. for giggles I called a supplier and got quoted 7/8-6 RH acme HSS hand tap $175 shipped to me. not cheap...but cheaper than $250.
 
That's kind of where I thought you might be going with this. If someone happened to have that tap, you could thread your own stock. But the taps are spendy buggers, even used. I believe John purchased nut blank(s) from Roton similar to this. https://www.roton.com/family/acme-right-screws-and-nuts-7060204/

I thought I read somewhere guys were hand tapping their own lead screw nuts & if I recall it was ok if you were making your 2-part adjustable (anti-backlash) because you could tweak it a bit. But straight hand tapping single thread was not recommended & I'm not sure why. Thread tolerance on the tap maybe or related to brass/bronze material maybe? I would not have thought it would be a problem but I've never made one before & cant recall the link or reason off hand.
 
I cut an internal 7/16 acme once on a lathe . I was able to borrow the threading bar from work. It was cut in the end of a mild steel shaft. It took a lot of passes but wasn't that bad. I think it would be a piece of cake on a Cnc lathe.
 
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