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Creating datum from rounded slot

Hello, in the beginning i want to emphasize that i'm a new use of pc-dmis software (4 months) and worked with the other software (ArcoCad) for 3 years.
Now I'm stuck with one thing in XactMeasure GD&T. I got part that has datums like in the drawing.The problem is that I'm not sure if I created datum C in the right way. I simply measured auto-feature round slot and then defined it as a datum C. Now, when I create a dimension with XactMeasure, PC-Dmis creates an FCF alignment that I see on CAD as yellow arrows. But when I think about it and talk with my colleagues, I started to think that it should look like the red arrows. And now, if I create a centerline from the slot to create datum C from it, I will not be able to use the MMC in this datum.

I checked the forum topics, but still have not find a solution:
https://www.pcdmisforum.com/forum/pc...und-slot/page2
https://www.pcdmisforum.com/forum/pc...h-length-bonus

PS. I am not the best in English because I do not use it very often, but I hope that my post is understandable, if not i will try to explain in further.

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  • I think I would agree with PC-DMIS, since this is more inline with how a mating part would align to the datums. Your results will be much more consistent because the line from centroid of B to the centroid of C is much longer than the centerline of C is. If you clock to C only, and the angle is just slightly off, this error will by projected out and will be worse the further away you get from the datums.
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  • I think I would agree with PC-DMIS, since this is more inline with how a mating part would align to the datums. Your results will be much more consistent because the line from centroid of B to the centroid of C is much longer than the centerline of C is. If you clock to C only, and the angle is just slightly off, this error will by projected out and will be worse the further away you get from the datums.
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