Lead Screw not turning consistently

[Jim F]

I believe the OP has a PM1440GS which has a selector knob for inch or metric threads and says it works fine in the metric position which would rule out the shear pin.

Not familiar with these new machines, my lathe was built in 1947.
Just the way the shaft was turning made me think shear pin, being a mechanic for 40+ yrs.

 

[LTRDavid]

Well the lead screw turns consistently as described in my last post, but not in time. I have it set to cut 16 TPI but I’m getting something greater.

 

[LTRDavid]

I was able to measure the threads at 28 TPI. Then I saw on the thread chart 28 TPI is the #8 position. So I took the front cover back off and repositioned the dial from #1 to #8. Put the front cover back on & turned the knob from #8 to #1. Reblued the tenon & did another scratch cut.

I’m back at 16TPI!

 

[LTRDavid]

Well, I still managed to get the tenon completed today. Next comes chambering.

 

[jbolt]

Well, I still managed to get the tenon completed today. Next comes chambering.

Glad to see you got it sorted out.