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GD&T Question

See attached image. Datums F and G are in line cylinders. The feature control frame says to check total runout of each F and G to an F-G alignment. This call out has always puzzled me. Doesn't total runout require that you check a feature to one other datum? For example, I could check F to G, or vice versa. How would you check the total runout of these datums to themselves?

Geometric Tolerancing in PCDMIS 2022 is relatively new to me, so I could be doing it wrong, but I've noticed that if I try to dimension a feature that is one of the datum's in the control frame, I get an error telling me I can't do it.

This feature is on a large part, so rotating it is not an option. Both the F and G cylinders are being scanned as circles at various depths. Cylinders are then constructed for both F and G.

So my questions are:

• Is this call out correct?
• If it is correct, how can I construct it to report correctly?
• If it's not correct, what's the best method to check this?

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  • you could program a Del-Tronic pin and report it the same to get the result. Basically you are treating the deltronic pin as a standard. This will let you know if its a machine error, probing error or software issue. I see this type of FCF a lot and if our shop makes the "F" and "G" datums on the same set up then turns the middle ID we see out of tolerance conditions, if they machine the middle ID then the Datums they are normally within .005 MM. definitely throw some form control on them for reference.
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  • you could program a Del-Tronic pin and report it the same to get the result. Basically you are treating the deltronic pin as a standard. This will let you know if its a machine error, probing error or software issue. I see this type of FCF a lot and if our shop makes the "F" and "G" datums on the same set up then turns the middle ID we see out of tolerance conditions, if they machine the middle ID then the Datums they are normally within .005 MM. definitely throw some form control on them for reference.
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