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Keep Surfaces Coplanar with Profile
(In accordance with Y14.5M-1994 standard)

PDF of this Tip

It is often necessary to have two or more surfaces act as though they were one. That means that you want the surfaces to be located relative to one another regardless of referenced datums. There is only one geometric tolerance that locates surfaces-profile of a surface. The drawing illustrates two ways to control the location and orientation (parallelism) of two nominally coplanar surfaces. If the parallelism approach is used, the surfaces might be parallel to the datum plane but would not be controlled for coplanar to each other.

By using composite profile of a surface, coplanarity is controlled as well as parallelism. Therefore, the surfaces may float up and down within the 0.4mm tolerance zone which is centered on the 25mm BASIC location but they must float together while remaining parallel to the datum plane within 0.1mm.

Back to Tips Tip added Oct 2004