It Is Referencing the Datum - Not Itself (#158)
(In accordance with Y14.5M-1994 standard)
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I often get the question, "How can a feature reference itself in a feature control frame?" The answer is, "It can’t." Datum features referenced in a feature control frame are establishing a datum reference framework which serves as the origin of measurement. The shaft shown has two total runout controls that appear to be referencing …
