First, if your converting an old knee mill you will NOT get 0.0001" accuracy. Even if you add brand new fancy ball screws and such you'll see more error from cutter deflection, cutter wear, material changing size as it heats/cools, etc, etc.

Second, Mach will always send out enough pulses to go where you tell it to within the resolution of your steps/unit. If you only have 2,000 steps/unit then you will see some non-cumulative rounding issues at certain numbers (as everything is broken down into 1/2000" increments). Again, lets stop and consider what that 0.0001 means in the real world...unless you have a very hi precision machine, operating in a temperature controlled environment, that you have done screw mapping on, let warm up to two hours before cutting parts,etc, etc; you just won't see it.

Absolutely agree with everything you say Jeff regards *real world* accuracy. BUT why is Mach giving the results it is? His steps/per *must be* integral denominators of his units otherwise his 2nd, 3rd, etc moves would not be EXACTLY 100.0000 units apart in Mach.

Ian

It is probably just the way he is grabbing the position. No need for fancy macros here, as other have suggested just command a move in the MDI and then look at the DRO...