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Basic Dimensions and General Feature Control Frame

seppley
I have a quick question.

I have been told by corporate engineering to take the General Notes, Surface Profile Feature Contrl Frame on the drawing and apply it's tolerance to the basic dimensions. Is this the proper way to utilize basic dimensions? I thought that basic dims were "Theoretical Exact Dimensions" and had no tolerance. How do you guys report them? I have just been reporting them with a zero +/- tolerance.

Thanks

Sam
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  • The way I do things for our engineering group, and keep in mind, I'm inspecting my own company's parts...I don't report basic dimensions, per se. If a hole pattern is defined on the drawing using basic dimensions, and then "located" with a feature control frame, I use Exact Meaure, define the datum features, and set up the FCF in PC-DMIS, then use text only reporting, and accept the default (out-of-the-box) report template. Now, the ExactMeasure will show where each hole is along the axes, will show the size it measured, and then report any datum shift if there is a composite FCF. I do not go back and use the location dialog box to report the basic dimensions themselves. I let the FCF and Exact Meaure do all the heavy lifting. Simply because, if there is any modifier on the feature, (MMC, LMC) each hole has to be treated differently, and will have a different tolerance, based on those modifiers.
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  • The way I do things for our engineering group, and keep in mind, I'm inspecting my own company's parts...I don't report basic dimensions, per se. If a hole pattern is defined on the drawing using basic dimensions, and then "located" with a feature control frame, I use Exact Meaure, define the datum features, and set up the FCF in PC-DMIS, then use text only reporting, and accept the default (out-of-the-box) report template. Now, the ExactMeasure will show where each hole is along the axes, will show the size it measured, and then report any datum shift if there is a composite FCF. I do not go back and use the location dialog box to report the basic dimensions themselves. I let the FCF and Exact Meaure do all the heavy lifting. Simply because, if there is any modifier on the feature, (MMC, LMC) each hole has to be treated differently, and will have a different tolerance, based on those modifiers.
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