Posts by jpbelanger

The New ASME Y14.5-2018 Standard

Posted by on May 24, 2019 in 2018 ASME standard

Well, an updated version of the GD&T standard has been released! Although released in 2019, it carries the date of 2018 (big things move slowly, right?) For those of you who use GD&T regularly, it’s probably worth the money to buy the new standard from ASME (either hard copy or PDF — same price). I’m still absorbing some of the changes, but for now I’ll mention a couple of significant things… The most notable change is the deletion of concentricity and symmetry from the standard. You may already know that these two symbols have been confusing, because they were often misused or misinterpreted. (See our past blog post here for a glimpse into concentricity.) So now the main choice for location will be position, but profile or runout symbols can also be used to control coaxial features. …there are some other things in the new standard, but these are the main ones for now. Another change to the standard was the addition of a new modifier called “dynamic profile.” It’s a little triangle symbol that can be placed within a profile’s feature control frame (after the tolerance number), and it means that the profile zone controls form (which profile usually does) but not the size of the feature. For...

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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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