This question was answered a year ½ ago right? I only ask since however unethical we all agree it is a legal callout. Also agreed when -A- is parallel to -B- you’re going to have problems. But then Rick never joined back in and while this topic has resurfaced it has brought to light another question. Can you easily construct a cylinder from the larger diameter Tim says is raised 1/8th inch? Well, Zeiss Usoft offers an option to measure a hole in sheet metal as a cylinder so my answer is unconditionally yes. This is how it works: I’m sure many of you have seen the perpendicular call out of a pierced hole in sheet metal back to -A-. In the case with Rick’s part using Usoft you would first measure a plane on the flat raised surface. Assuring that surface is perpendicular 90 degrees to -B- the cylinder axis will follow the same orientation of that plane. Then select (1) elements (6) cylinder (F7) input knowns (F4) direction (F4) plane (F4) search for the plane previously measured or enter the element number of that plane, hit enter to accept (F2) point data, enter the number of points you wish to take about the cylinder or hole and take your hits, minimum of 3 (F3) select tolerance/enter tolerance (F6) Remark (F5) input text, label your feature hit enter to accept (F1) printer store.

There is no need to measure two sections of the feature to construct the cylinder. As I said, you can do this on paper-thin sheet metal. The hits can all be on the same level and you will still get a line axis through the center of the hole or raised surface in this case relative to the aforementioned plane. To that line axis you apply your primary datum or 3D alignment - line.

Regards,

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