True position reports zero for Z location on threaded holes

[[Th...]]

I’m measuring the true position of two threaded holes using the legacy true position with datum B primary and A secondary. The Y results vary, but the reported Z location is measuring zero. Nominal location being zero.

When I switch from a diametral Y/Z tolerance zone to a polar zone, Z variation appears but the drawing does not specify a projected tolerance so I don’t want that. I also changed a feature’s nominal Z from 0 to 0.100 as a test, and its actual Z then reported 0.1000.

Anyone know why this is happening? Given the datum structure, rotation is free so is Calypso forcing the feature to the perfect zero? If so, is this ok to leave like this?

Note: I’ve also tried using a bore pattern and freeing the rotation.  When I do there is variation in both Y and Z but of course TP results significantly increase since there is now another variable to include in the error. 

[[Ma...]]

Hi,

can you describe what feature you used for threads?
What are those datums B and A.
How your TP callout looks like?

Drawn sketch would help also.

[[Jo...]]

you openend two threads for the same topic?

[[Ma...]]

From what you are describing I'm picturing having a face as A and a diameter as B origin and threaded hole off center in Y, but 0 in Z..... Since you have no clocker Z will always report as 0...... One thing to watch out for is if you have multiple features on the part is that they still have to meet your angular tolerance even when relationship is not specified directly.... For instance, if your general angle tolerance allows ±1° and you have a slot on side of the part and a hole on the face, those two still have to be within 1° even when not specified.

 

If possible at all, I always add a clocker based on what they are doing on the CNC machine.... This helps them tweak the rotational relationship between features

[[Th...]]

Jochen, 😂 yes I did. Originally in the CMM/VMM but then I figured the general topic would yield more replies.

Marcel, you’re right the 2x threaded hole callout are off center in the Y. The datum’s is A as a diameter and B as a face.

But I suspected it has something to do with the rotation and a Calypso forces the feature to the perfect zero. I’ve opted to trust in the software and leave as is for now.