Don Foreman wrote:

DoN Nichols wrote a little program that John Beidl made usable under
Windows. I've been using that for years.
http://www.metalworking.com/dropbox/...s/Threadsw.txt
The one I use is v5.0.0.0, 2 Mar 99. It's worked on every Windows
machine I've owned, currently running Win XP Pro.

A formula that seems to work for internal threads is:
ID = OD - .975/TPI

I made a spreadsheet with these values and printed a chart that is
taped to my lathe.

Thanks for the program tip.

It's a guide, not gospel. I've made parts to fit a mating part 1500
miles away (and they did) but with internal threads it's really best
to have a try gage at the lathe if at all possible. Perhaps not so
true with ultra-rigid CNC machinery, I don't know anything about that.

Oh heck, I'm not using CNC, I'm using my Clausing 6903 engine lathe.

I managed to cut a thread that feels okay but that was after I used the compound to go in
..700 deep to start a relief cut for my threading tool to run out into. Well that didn't
work out so well. I had a relief .350" from the end of my stock. Darn compound reads
half values. I can understand that on a cross feed, but it doesn't make a lot for since
on the compound. Oh well, I'm getting to know my lathe by trial and error.

Thanks Don(s)

Wes