General

This Section establishes practices for expressing tolerances on linear and angular dimensions, applicability of material condition modifiers, and interpretations governing limits and tolerances.

CAUTION: If CAD/CAM database models are used and they do not icclude tolerances, then tolerances must be expressed outside of the database to reflect design requirements.

2.1.1 Application. Tolerances may be expressed as follows:

(a) as direct limits or as tolerance values applied directly to a dimension (see para. 2.2);

(b) as a geometric tolerance, as described in Sections 5 and 6;

(c) in a note referring to specific dimensions;

(d) as specified in other documents referenced on the drawing for specific features or processes;

(e) in a general tolerance block referring to all dimensions on a drawing for which tolerances are not otherwise specified; see ANSI Y14.1

2.1.1.1 Positional Tolerancing Method.

Preferably, tolerances on dimensions that locate features of size are specified by the positional tolerancing method described in Section 5. In certain cases, such as locating irregular-shaped features, the profile toletancing method described in Section 6 may be used.

2.1.1.2 Implied 90° Angle. By convention, where center lines and surfaces of features of a part are depicted on engineering drawings intersecting at right angles, a 90° angle is not specified. Implied 90° angles are understood to apply. The tolerance on these implied 90° angles is the same as for all other angular features shown on the field of the drawing governed by general angular tolerance notes or general tolerance block values. Where center lines and surfaces of a part are depicted on engineering drawings intersecting at right angles and basic dimensions or geometric controls have been specified, implied 90° basic angles are understood to apply. The tolerance on the feature associated with these implied 90° basic angles is provided by feature control frames

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