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Reporting Profile
(In accordance with the ASME Y14.5-2009 standard)

PDF of this Tip

People seem to understand when inspecting and reporting position they need to determine the deviation from the basic location and double it to compare the measured value to the allowable tolerance. However, for some reason, doubling the largest variation from the true profile to compare the measured value to the allowable profile of a surface tolerance doesn’t seem to be as obvious. Here is an illustration that I hope will clear up any confusion that might exist.

Let’s start by determining if this part will pass the profile tolerance.  Since the tolerance in the feature control frame is always a total value and is implied centered on the basic location, the indicator reading cannot be more than ± half of the profile tolerance of 0.3 which would be ±0.15.  Since the largest reading is -0.12, the surface is within the profile tolerance.

Now the question is, "How do I report the measurement?"  I recommend that the two extreme measurements be noted.  This will help production adjust their process.  However, often engineering or the customer want one number that they can compare to the tolerance on the drawing.  So, in addition to reporting the deviations, you should report the total width of the tolerance zone needed to accept the part. That tolerance width would be twice the largest deviation.  In this case, you would need an allowable tolerance of 0.24 (2 X 0.12).  This approach works unless the profile tolerance is unequal or unilateral.  Reporting those tolerances will be covered in a future Tip once the Y14.45 committee on Measurement Data Reporting has published their standard.

Back to Tips Tip added Feb 2012