finding the apex of a cone on a small surface

finding the apex of a cone on a small surface

Hi All,
I have a 11.5 inch base diameter cone, 60 degree angle. The angle is appoxamently 1 inch thick. I need to find the apex of the cone. This is my datum A.

CMM manager is giving me a number that is about .015 to large, would this be accurate or is the beeping area to small to calculate.

Thanks Laura