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For Coplanarity Use Profile
(In accordance with Y14.5M-1994 standard)

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Flatness is an individual control. When you want multiple surfaces to lie in the same plane the Y14.5 Standard says to use profile. Many designers and engineers think that if flatness is used in conjunction with an extension line, it means that the surfaces must be contained within two parallel planes with a maximum separation not greater than the specified flatness tolerance. As illustrated, however, this is not the correct interpretation.

he desired condition is called coplanarity. The correct method to control coplanarity of multiple features, is by using profile as illustrated below.

Back to Tips Tip added Jul 1998