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Have Your Datum Reference Frame and Satisfy Others
(In accordance with Y14.5M-1994 standard)

PDF of this Tip

Often people are troubled when the planes of a datum reference frame do not appear as vertical or horizontal centerlines on the drawing. On this drawing the second and third datum planes of the datum reference frame established by A, B, C are not vertical and horizontal. The dimensioning and tolerancing is easier to read/understand if two additional mutually perpendicular planes are added to the drawing. The intersection of these planes is a line coincident with datum axis B. They are oriented 52 degrees BASIC from the actual datum planes of the datum reference frame. As long as all of the features on the part are tied together by basic dimensions, this approach to dimensioning may be used.

Note: For clarity, this drawing is intentionally incomplete.

Back to Tips Tip added Jan 2004