Geoff;
I agree with you that the CMM is a great way to check parts, quick, accurate, for most things that "WE" inspect but I still find that for some of are larger parts (24.000" x 6.000"x 2.000" for a flatness of .015 tot./.001 inch per inch) it is quicker and easier, and more accurate to check flatness and/or parallelism using 3 jack stands, surface plate, height gauge, dial indicator, though I do use the CMMs flatness function to confirm some of are smaller areas of flatness (2.000" x 3.000" areas for a flatness of .001), but as I said at the start if the machine shop does a good job on the holes of a part (leaving them nice and clean with NO burrs/tool mark's so that there are no bad hits) you should get good result's, though if we find bad parts from the CMM we will find a 2nd. way to check the 1st. part off the CMM

John D. Ruys
CMM programer/Inspector
Teledyne MEC