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Extent of Profile Tolerances
(In accordance with the ASME Y14.5-2009 standard)

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The ASME Y14.5-2009 standard is a little confusing with regards to specifying the extent of a profile tolerance. There is a drawing in the Standard that gives the impression that the extent of the profile tolerance includes both radii as shown.  Others will argue that the profile tolerance only applies to the one radius contacted by the arrow on the leader.

You can take that risk if you want, but it is an unnecessary risk.  The Standard provides us with the between symbol, shown on the second drawing. By using the between symbol you can remove all doubt regarding the extent of the profile of a surface tolerance.  This profile tolerance clearly defines the tolerance zone illustrated.

Some folks go overboard trying to help the people who haven’t bothered to learn how to read a drawing while others seem to try to see if they can trick the reader.  We need a nice balance that lies somewhere in between.

Anyone making a drawing should make every effort to make the drawing clear to those who know the Standard.  Anyone making or inspecting parts or approving drawings should make every effort to know how to read a drawing made in accordance with the standards.  What doesn’t make sense here?

Back to Tips Tip added Mar 2014