J
I don't think you can "eyeball" the difference between, say .018 and .021 on a radius gauge, especially when the radius is only 5 or 10 degees of the arc. If I filled out on an inspection report, "method of inspection" as "eyeballing", they'd laugh me out of the corps! We had a vendor and a customer checking some samples with their CMMs, and got different readings. I guess .020 is too small for CMM... different placement of the probes makes a big difference.

