We find problems on measuring the recess depth. As you may know since the end surface of the recess is not blind,(If so, it can be measured by a height gage, right?) while it is actually a conical end.

What approach of measurement should we try? as we know that it would be possible to measure it by CMM, or cut the section right away to be inverted in projector for dimensional measurement, am I right? Any other possble method ?

But if in situation that do not allow for the use of CMM or cutting parts approach, how can we measure it it a simpler and/or cheaper way? Would you please suggest me some ? Thanks alot!