Interpretation of Limits (ASME)

Some might look at the limits of a tolerance zone as non-absolute, but is that correct? ASME standards tell a different story for Interpretation of Limits.

When reading tolerances on engineering drawings, one of the finer points that comes up during Quality inspection is how to interpret tolerance limits.  Some might look at the limits of a tolerance zone as non-absolute.

In other words, if a feature measures 14.004, but the upper limit specified on the drawing is 14.00, then one might be inclined to accept the part because 14.004 can be rounded to 14.00.  However, according to ASME Y14.5-2009 (and any earlier versions), this is false reasoning.

All limits are absolute.  Dimensional limits, regardless of the number of decimal places, are used as if they were continued with zeros.

The example given is similar to this: 12.2 means 12.20…0 (zero to infinity).

So, with that clear statement, interpretation of limits is always absolute.  A measurement of 14.004 is a nonconforming part if the upper limit is 14.00.  This is important, as it eliminates ambiguity and the opportunity to fudge with the numbers in a way that can affect quality and even product definition over time.