In order to set up the CNC software we need to know the pitch of the leadscrew being used. I found a Pitch Conversions Table to help with this. I have purchased a 6ft 1/4″-20 (20 threads per inch) threaded rod to use as a leadscrew. According to the table this is a pitch of 1.27mm.

With 200 steps per revolution that will give 6.35um per step. Using 1/16 microstepping that should give an average of 0.397um per microstep. However there will likely be a bit of play between the nut on the leadscrew and the leadscrew, eroding this accuracy somewhat. Also the threaded rod and the motor are made to specific tolerances and are not exact.