In order to detect that the size is being controlled, two-point measurements must be made. The hole illustrated above would pass a NOGO pin but would fail a two-point check as shown below. In other words, this hole fails a proper inspection of size.
When size is really important, throw away your NOGO pin gages (#12)
(In accordance with the ASME Y14.5-2018 standard)
(In accordance with the ASME Y14.5-2009 standard)
(In accordance with Y14.5M-1994 standard)
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According to Rule #1 of the National Standard, the least material size (largest internal feature or smallest external feature) of a feature of size should be verified at each cross section. NOGO pin gages do not detect form errors. If a hole, for instance, is out of round (which they usually are) a NOGO pin will not detect that some cross sections of the hole are actually larger than the size will allow.
This Tip is in accordance with ASME Y14.5M-1994, ASME Y14.5-2009, and ASME Y14.5-2018. Tip was originally released in May 1998.
