I have a bore that is Datum B. It has a perpendicularity callout to Datum A, which is a flat surface. So, I have to measure it as a cylinder. I have another bore that has a circular runout callout to AB. So do I have to measure B again as a circle? Because I would have to assign that as another datum to build the feature control frame. But if I just use B as a cylinder, then wouldn't it be measuring total runout and give me a different result than circular runout?
Circular Runout of a plane to a datum cylinder is unusual but allowed. It's basically checking a bunch of concentric rings on the face, one ring at a time. Total runout checks the whole face at the same time within a tolerance zone of 2 parallel planes.
I think the idea is to have Circular Runout refine Total Runout.
The intent of the control is to limit "in and out" movement of the face as the part rotates. As a test, you could dimension perpendicularity of the plane to the cylinder and see how those results compare to your runout dimensions. I'm not certain of the math differences but it would be interesting to compare.
Circular Runout of a plane to a datum cylinder is unusual but allowed. It's basically checking a bunch of concentric rings on the face, one ring at a time. Total runout checks the whole face at the same time within a tolerance zone of 2 parallel planes.
I think the idea is to have Circular Runout refine Total Runout.
The intent of the control is to limit "in and out" movement of the face as the part rotates. As a test, you could dimension perpendicularity of the plane to the cylinder and see how those results compare to your runout dimensions. I'm not certain of the math differences but it would be interesting to compare.
