Thanks for your reply. I think that I am not using enough power for the stepper motors which in turn is leading to the lost of steps. I have ordered a new higher rated power supply. One one thing that puts me off Linuxcnc is going backwards with using a printer cable. I know that the 100khz is not the best breakout board however it’s one good point is it automatically sets the ports and pins. I remember years back pulling my hair out with ports and pins. As to what I am trying to calibrate, we’ll that would be the movement of the axis to match the distance given in mach3. So the motor moves the correct distance to what mach3 thinks it has moved. I will wait until the new power supply turns up and start playing again Thanks for your help.