Non-constant Pitch when Threading on Lathe

[markba633csi]

I had the same issue cutting 16 tpi, it seems easier to notice when spindle and leadscrew are in that 1:1 ratio-
In my case it was a binding tooth on the leadscrew gear
Mark

 

[pdentrem]

So I took make leadscrew to a larger lathe and made a skim pass on the thrusting surfaces to get them true to the axis, then made a proper bronze bushing for said surface to ride against, and I’m happy to say that all is well. At the end of the day, I think only one of the two steps above is really necessary to fix the problem if you’re in a pinch and can’t work on the leadscrew. Thanks to all again for all the help and suggestions!

At least now you know that both are right and problem fixed!