Do you have the steps per unit set correctly?
Are you skipping?
Is backlash set correctly?
Is the velocity and acceleration settings appropriate for YOUR machine?
Is the tool perpendicular to the table?
RICH
FWIW,
0.09" is lot to be out, heck, one can use an acme threaded rod with nuts to drive the axis and get closer. In fact that is what a friend had for his lathe
which had 1/8" backlash and he could cut darn good threads with it!