Im using Mach4 hobby on a Shopmaster lathe with a smoothstepper ESS.  The problem is when threading to match a standard nut the TPI is off. I was just threading a rod for a 1/2-13 nut. I had the pitch set for .796 as the specs say and the threads were a good bit to coarse. I set it down to .725 and its closer but still too coarse.
All the settings are right, the pulses per unit is correct (1" equals 1" travel) and using one pulse per spindle rotation with a clean scoped pulse.
Can someone please help me find out why this is happening?
Thanks