I've been having an issue measuring concentricity. Could someone explain best practices for checking concentricity between two holes/pins at opposite ends of a part? The parts very from 4" to 12". I can spin them on the datum on my V-Blocks and show them as basically perfect with an indicator (indicator/v-block has been certified), but when I run them on the CMM I show them as being out of tolerance by like.. 1mm~/0.040". I have no idea if I'm just setting up the feature wrong or what, any thoughts?
I've at least partially figured it out after playing around with it for a little while. It seems that the vector of the cylinder (DAT-A) heavily influences the concentricity? I don't know why. If I construct a cylinder around DAT-A and reverse the vector, the measurement becomes closer to what I would expect to see on this part.
Also to answer your questions:
-Yes, I'm measure the full length of the datum as a cylinder (approx. 25mm)
-3 levels with 6 points on each level for the datum
- 9 hits for the feature that's being held concentric to the datum
I've at least partially figured it out after playing around with it for a little while. It seems that the vector of the cylinder (DAT-A) heavily influences the concentricity? I don't know why. If I construct a cylinder around DAT-A and reverse the vector, the measurement becomes closer to what I would expect to see on this part.
Also to answer your questions:
-Yes, I'm measure the full length of the datum as a cylinder (approx. 25mm)
-3 levels with 6 points on each level for the datum
- 9 hits for the feature that's being held concentric to the datum
