I too have the same Questions. I even went out and purchased Scott Beavers DCC CMM Programming book hoping that it would solve all my alignment problems. While informative, it really provided little in this area. I have a similar issue when setting up a Part alignment on a casting that has 3 datum points on the Primary Datum. They are set up in a triangular position with the datum A located in what would be the vertex of the triangle and the other points offset from Datum A by 17.2mm. I do not have a fixture so I am trying to ensure that my alignment is accurate as there is much room for measurement error if this plane and the related Perp. sec. and tert. axes are not correct!

Jesse Gentile
Quality Technician
AMAK Brake, LLC