Tuning motors issue

Alrighty....I have a little issue with getting my motors tuned in Mach3. This is actually on my Clausing lathe conversion. Here is what happens:

I can get my motor set to move exactly short distances (.5, .625. and .750). But once I try a longer distance (6"), it moves .020" too far. If I get the steps set to get the longer dimension right on, then the shorter travels are off by .002 too short.

I am sure I am missing something simple here, but I cannot figure it out.

Oh...and just out of curiosity, I used the milling module and used the automated tuning feature....same thing happens.

Any ideas?

Mike

Sounds like you might have leadscrew issues and you may need to use the screw mapping feature of mach3.