Does anyone know of an ISO standard where the dimension would be underlined? I have a drawing with underlined dimensions and I am not sure what the underline represents.
I have seen an underline used were a dimension is shown out of scale for clarity (back in the day of manual drafting). If the dimension is a shown dimension and the model is regenerated, this could of course not be true. If the dimension is a shown dimension, check if the dimension text has been overwriten. If this is the case your model may not represent the design intent completly.
I have worked with some blueprints made back in the 60's where they combined the casting print with the machining print. All underlined dimensions were casting dimensions. There was also a note on the drawing that opened these tolerances up to make the casting easier.
Values for dimensions out-of-scale ( except where break lines are used) shall be underlined with a straight thick line
Dimensions out-of-scale can result from a feature size modification where the modification does not warrant an extensive drawing revision to correct the feature scale.