I measured the cutter @ 6.3mm.
I believe the problem is the motors are not big enough (NEMA 23 235 oz-in with a 2/1 gear reduction) to hold position while cutting. If I move the table using MDI, then plunge with the same end mill, measure between the holes, it is right on the money. Anyone have some suggestions for motor size? I was thinking 600 oz-in.