Norman,

The datum structure you have described is a legitimate call out. Assuming -C- is primary and -A- is secondary the features may be applied as follows: Pick up Base Plane -C-, then measure the Origin -A-, then measure -B- and construct a line for Axis alignment -B- (Line between -A- & -B-). As long as you "clock" the part or stop the rotation of the 3 planes XY, YZ & ZX you should be good to go. But wouldn't it make more sense if -C- were -A-, -A- were -B- and -B- were -C-? Also, for the description of -B- you have center plane, are you taking -A- and -B- as cylinders or diameters? If diameters, take them as close to the surface -C- as possible. There are still other possibilities, this would be my first attempt. Knowing the engineers intent would help as well in order give priority to the datums ie., primary, secondary and tertiary. Hope this helps.

Regards,

Geoff
Sr. CMM Programmer
Lapeer Metal Stamping
LMS Metrology Lab
Lapeer, MI