Noncircular Features

The fundamental principles of true position dimensioning and positional tolerancing for circular features, such as holes and bosses, apply also to noncir-cular features, such as open-end slots, tabs, and elongated holes. For such features of size, a positional tolerance is used to locate the center plane established by parallel surfaces of the feature. The tolerance value represents a distance between two parallel planes. The diameter symbol is omitted from the feature control frame. See Figs. 5-43 and 5-44.

^ Datum plane B

Datum plane A

0.04 wide tolerance zone

True position related to datum reference frame

70* datum D

0.2 wide tolerance zone

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