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Keep Control of Datum Features Simple
(In accordance with Y14.5M-1994 standard)

PDF of this Tip

Frequently, designers use one or two features within a pattern as datum features. On the part shown, it is desirable to use two of the holes in the three-hole pattern as datum features. One approach would be to apply individual controls to each of the holes in the pattern as the first drawing illustrates. Another approach is to control the holes as a pattern using position relative to the primary datum, A. Then, label individual holes as datum features as shown in the second plan view. Depending on the tolerances and modifiers used, nearly the same control may be achieved with two less geometric controls, which simplifies the drawing and may simplify verification while meeting functional requirements.

Back to Tips Tip added Feb 2001