Anyone able to do metric threading want a small project?

[frontrange]

First, forgive me if this is the wrong forum for this. I'm working on converting a Logan 12X36 lathe to CNC and I've got a small problem. I got a very sweet deal on a really nice ground ball screw for my z axis. I was able to get it properly sized on the floating end after spending a whole day going at it with a tool post grinder. Today I'm going to assemble it and discover my fixed end nut won't screw on past the first thread or two. Turns out they threaded the M20 end of the screw at a .8mm pitch instead of a standard 1mm.

So anyone able to turn me a new nut for a reasonable fee? Or if anyone has an idea where I might source one I really would appreciate it.

TIA/Steve

[juergenwt]

Frontrange - There is no M20 x 0.8
Most likely you have M20 x 0.75
Check again.
Check with "Maryland Metrics" for a Nut or a tap.

[frontrange]

Nope, it really is M20x.8. With surplus ball screws you get what you get.

[nusolar]

Have you tried to contact the company who made the ball screw ?
I could make a nut for you if you can't locate one,let me know

[frontrange]

Afraid there's no way to identify the source of the ball screw. All I know is it's hardened all the way through (good thing I have a toolpost grinder, carbide wouldn't touch it) and preloaded with a double nut. I'm sure someone paid a bunch to have it made.

If you could just turn an internal M20x.8 for about 1/2 inch or so on a piece of scrap I can do the rest. Metric threading is the biggest reason I'm doing CNC on this lathe. Everytime I run into a metric issue it is a showstopper for me.

Please let me know how much and if PayPal is ok. And thanks a bunch!

[RotarySMP]

Can your lathe do 32tpi?

0.8mm pitch is 0.0314". 1/32" is 0.03125".

If you turn a 20mm x 32tpi thread your theoretical lead error is only 0.00015" per thread. Sounds close enough for me.

I could turn a 0.8mm pitch thread, but have no reference gauge to determine when the thread is done. The chances of my thread being any more accurate than you turning a 32 tpi thread and trying it out on the screw it needs to fit is slim.

[frontrange]

I have about 12" of ball screw I cut off, including a sample thread. But your point is a good one, 32TPI may be close enough. I'll give it a try and see how it fits!

[nusolar]

turnning and threading is no problem for i have CNC's I would use, but as posted before gaging and or checking is a concern.does your manual lathe have metric gears ?

[frontrange]

No, Logan metric interposing gears are insanely expensive, money better spent on CNC conversion which is what lead me here in the first place. I did cut a sample 32TPI and checked it with a thread gage - looks close enough.