Caliper distance not matching additional result on true position?

[[Lu...]]

Hello, I was asked to give the Y and Z result for a hole in relation to another hole. The characteristics i am having issues with are 2 holes facing towards X-, and about an inch apart of each other in the Z direction. The Z distance was already reported since it was a dimension on the print, but there was no Y distance (it was not fitting on a gage, so they wanted to know where they were in relation to each other for adjustment) they are supposed to be in line with each other on the Y, so if I had used another caliper or cartesian distance it would only show how far away they are from Zero, not which direction.

So i decided to use a reference GD&T true position, with loose enabled so i can use a coordinate system as the datums. I made the coordinate system use the bottom hole as my zero, and a 3d line between the 2 holes as my planar rotation. I enabled additional result on the true position so it would report the Y and Z, and i also used the alignment i had made on the caliper distance I use to report the Z as well so they would have the same orientation when calculating the distance.

I have noticed that the additional result and the caliper distance report to be different about .0001-.001 each report (it is different between every part, but on average its about .0005 inches) this has caused people on the floor to ask me why and I have spent a lot of time trying to figure out why and I cant seem to get any better results than that. 

I threw together a quick drawing to help explain better, If you have any questions please let me know. Thank you very much for your help!

 

[[Lu...]]

Actually thinking about it again I have no idea how I am getting a Y result besides 0, since it is using the top hole as the orientation 😖 I have quadruple checked all my alignments and nominals and everything and it all seems to be correct... still very confused any advice is appreciated

[[Ke...]]

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Did you confirm that the Evaluation Settings (Outer Tangential, etc.) in your alt method are appropriate for the standard that you are using?

Edited 2 hours ago

[[Lu...]]

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Yes, they are all correct. i have also compared them to the caliper distance and they are the same. Though could it be that im using a GD&T true position instead of a normal one? I see in the evaluation parameters there is a box about "point separation" which im not sure what that means. I believe I had tried comparing the normal true position and the GD&T true position results and neither of them matched in the past, but I dont remember for sure... When I get a minute I will test that again just to make sure

[[Ra...]]

I'd take a look at what characteristics you are using. Caliper distance will use the measured points of a circle, while a constructed 3D line out of circles will be referencing the center point of said circles. I imagine there is a disconnect somewhere in there. Try a simple distance just for fun.

 

Edit: I forgot you can determine CAD entities or measuring points when using caliper distance. Which one are you using?

Edited 1 hour ago

[[Lu...]]

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Changing it to the normal true position didnt change the z at all, though it changed the y by .0001

 

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Looks like its on CAD entities, though that is the only option available in the dropdown. Honestly I'm not sure what that means, does it mean that the original feature was clicked on the cad model instead of picked up manually then edit the nominals afterward?