semi-spherical disc

[[Da...]]

This could fit into software - calypso thread, but anyway:
How to qualify semi-spherical disc, how to be shure one does touch the "max radius" points?
Haven't really digged into, I assume check with ring gage is a must, but even then, what happens to geometry? Would the X, Y (Z) really be where it should be if I do a radius correction?

disc1.PNG

[[No...]]

Like you already mentioned, checking with a ring gage (and correcting the radius) is a must. Apart from that you usually probe a number of points above and below the sphere equator. That should give you X and Y pretty accurately. If you have doubts about the Z value, take probe points with the flat faces on the reference sphere (or on a fixed probe tip if the disc is very small) in +Z and -Z, calculate the symmetry and correct Z accordingly. Lots of manual work.