I have holes that I could only create as single point circles (they are 4-40 threaded holes) that have a true position call out. I created a position dimension and matched the feature control frame to the drawing (using 3 datums) but PC-DMIS reports failure that is far out of tolerance. When I looked at each of the basic dimensions I found that the y and z basic dimensions are close to nominal but the x dimension is far out of nominal. With the datum structure i put in and the CAD model, PC-DMIS designated the x axis going into/out of the part which is not relevant to the callout. How do I get PC-DMIS to calculate the position solely on the y and z planes?
What's your workplane? That is the axis you don't need. So if you're working in Xplus or Xminus, you don't need the X axis to be calculated into your TP measurements.
If you are using Xactmeasure, go to the advanced tab, at the bottom is a list of each hole, and check boxes for various parameters. Check/uncheck the parameters as required for each hole.
If I understand the OP correctly, he is measuring the hole as a point because it's so small, perhaps with a Romer or manual CMM. If that's the case, I don't know if perp to C/L will work.
generic circle, use the 'point' and the diameter from the single-point-circle, then dimension that, should be able to use all the standard position 'tricks' then (I would think, anyway)
