Using MACH 3 Ver. R3.043.062, USB Smooth stepper, PMDX 126,134 & Gecko 203V drives.
The motors have been tuned the problem is all cuts are 4 thousands smaller than they should be. The code checks out fine. Is there a setting in MACH that could be causing this problem?

Thanks
Bill I

4 thou?

In both directions?? Could be cutter wear, not a 100% accurate tool diameter?

The cutter used is new and yes the cut is smaller in both X and Y .

Have you done axis calibration using accurate measuring tools over a reasonable distance?

Yes  axis calibration has been done.

What kind of machine, and what are you cutting? Climb or Conventional?

Custom built CNC  Cutting MDF and plywood I cut in both Climb and  Conventional.

This is a new controller I never had this problem with  the previous controller.

Tool diameter set correctly?  Is the tool not the size you think?

Using 1/4" cutter  1st thing I checked was tool diameter.

Just a query - 4 thou on MDF - thats 0.1mm !

I would not think accuracy on MDF is possible in that range TBH.

I would be inclined to change the tool diameter using the wear factor (if used) by 2thou and try again but I'm still unsure if it is really possible.