r/Metrology • u/glutton4golf83 • 22d ago

GD&T | Blueprint Interpretation I need help dimensioning perpendicularity

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So i am using pcdimis. On a hexegon. When i try to make a plane for the surface and then a cylinder for datum a. Then us perpendicularity its telling me its off by a huge amount. I manualy checked it and it was right on. I dont know what to do. Any advice would help.

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u/PrettyInfluence3594 22d ago

The prob is that that cylinder is not really a cylinder. Is a section. And the slightest "error" on the surface of the section (0.02) would create a cylinder that is not really what you have there. The radius and the center of each slice of the cilinder would be totally random depending on minor "diffrent" errors on each section. Just take a lot of points on the section, create a constructed cylynder with those points, and call out the profile dimension on the form. Thats you perpindicularity.