In this Question Line video, Jason answers the following question regarding reference dimensions on true position:  

If a diameter is reference () on the drawing, does that make the GD&T under the diameter callout reference as well?

Fig 1 Reference Dim wgdt controls 1

 

To answer this question, Jason walks through the above example assembly drawing to explain the scenario where a feature being controlled by position must have a reference size dimension rather than a tolerance on the size of the feature.  

 

 

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https://www.gdandtbasics.com/share-your-gdt-questions/ 

 

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