Orientation Tolerances

Angularity, parallelism, perpendicularity, and in some instances, profile are orientation tolerances applicable to related features. These tolerances control the orientation of features to one another.

S.6.1 Specifying Orientation Tolerances in Relation to Datum Features. In specifying orientation tolerances to control angularity, parallelism, perpendicularity, and in some cases, profile, the considered feature is related to one or more datum features. See Fig. 4-24. Relation to more than one datum feature is specified to stabilize the tolerance zone in more than one direction. For a method of referencing datum features, see para. 3.4.2. Note that angularity.

perpendicularity, and parallelism, when applied to plane surfaces, control flatness if a flatness tolerance is not specified. Tolerance Zones. Tolerance zones are total in value requiring an axis, or all elements of the considered surface, to fall within this zone. Where it is a requirement to control only individual line elements of a surface, a qualifying notation, such as EACH ELEMENT or EACH RADIAL ELEMENT, is added to the drawing. See Figs. 6-44 and 6-45. This permits control of individual elements of the surface independently in relation to the datum and does not limit the total surface to an encompassing zone. Application of Zero Tolerance at MMC. Where no variations of orientation, such as perpendicularity, are permitted at the MMC size limit of a feature, the feature control frame contains a zero for the tolerance, modified by the symbol for MMC. If the feature is finished at its MMC limit of size, it must be perfect in orientation with respect 1o the datum. A tolerance can exist only as the feature departs from MMC. The allowable orientation toler-

Profile Tolerance Symbol

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