incomplete radius

[stimpy]

Hello all I have a feature that is a stud with a diameter. The stud has no flat diameter it is a radius up to a diameter. I have a crude drawing of it how can I measure this feature. I tried a .5mm probe and defined the top as a circle at 0 depth but that did not work. Thanks in advance I know one or two of you guru's will know. v3.7 mr3

[#2#]

If that is all you need on the part, an optical comparitor would probably be your best bet. If you absolutely must measure it on the cmm, can you take hits around the "top" of the part to form a plane? Then, level that plane and make it your z-orgin. Create a circle with a z location of 0. Then, the tip should hit with the equator of the tip exactly at the level of the plane (plus or minus of course your machine's movement accuracy). Maybe that is what you tried.