Geometric Tolerance Symbols

Geometric characteristic symbols, the tolerance value, and datum reference letters, where applicable, are combined in a feature control frame to express a geometric tolerance.

3.4.1 Feature Control Frame. A geometric tolerance for an individual feature is specified by means of a feature control frame divided into compartments containing the geometric characteristic symbol followed by the tolerance. See Fig. 3-19. Where applicable, the tolerance is preceded by the diameter symbol and followed by a material condition symbol.

3.4.2 Feature Control Frame Incorporating One Datum Reference. Where a geometric tolerance is related to a datum, this relationship is indicated by entering the datum reference letter in a compartment following the tolerance. Where applicable, the datum reference letter is followed by a material condition symbol. See Fig. 3-20. Where a datum is established by two datum features — for example,

Geometric characteristic symbol

Tolerance

Diameter symbol

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