Oh, I get that much - how it works in Mach3, however, is a mystery. When you enter the correction points, do you enter the correction you want to apply, or the actual coordinate read on the external DRO? I try to enter correction points, but nothing happens. Perhaps this is a bug in that it only works in metric? It defaults the screw lengths to 1300, and the graph of corrections is in increments of 0.1. If this is a small bug, it would be a great help if it could be corrected, as I do everything in inches.