Posts by jpbelanger

Common Dimensioning Symbol Errors

Posted by on Apr 23, 2014 in Uncategorized

No matter how good a dimensioning system is — GD&T, anyone? — there will still be errors encountered on drawings, simply because there will always be human beings who are behind the creation of a new drawing.  And of course we all make mistakes.  But I want to point out a few of the more common mistakes that I encounter in my travels. •   Failure to include a diameter symbol in a feature control frame when needed.  I’m thinking particularly of position and perpendicularity. When tagging these tolerances to a hole or pin, you usually need to include the diameter symbol before the number, so that the axis of the feature is contained in all directions. There are times when a hole’s position tolerance should not use a diameter symbol: if you really only want the tolerance to apply in two directions.  But that must be clearly indicated by proper using of dimension arrows.       •   The next common error I’d like to review is similar to the first — using a diameter symbol when it shouldn’t be there!  I see this in feature control frames for circularity, cylindricity, circular runout, and total runout.  It might be tempting, because each of these is applied to...

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