GEOMETRIC DIMENSIONING AND TOLERANCING (GD&T) • Purpose is to describe the engineering intent of parts and assemblies • Uses symbols to specify geometric characteristics and dimensional requirements • Current GD&T standard: ANSI/ASME Y14.5M-2009 • Symbols for: • Form and profile tolerances, orientation tolerances, location tolerances, runout tolerances
GEOMETRIC DIMENSIONING AND TOLERANCING (GD&T) • Feature control frame
GEOMETRIC DIMENSIONING AND TOLERANCING (GD&T) • Examples of Modifiers • MMC – Maximum Material Condition • LMC – Least Material Condition
GEOMETRIC DIMENSIONING AND TOLERANCING (GD&T) • ISO standard of preferred metric limits and fits: In the dimension 16h11, the tolerance zone is specified by a letter and a number, I.e. h11. An uppercase letter indicates that the tolerance applies to the hole; a lowercase letter indicates the tolerance applies to the shaft.
GD&T • Basic Dimension: Theoretically exact, untoleranced dimensions that specify the perfect location, size, shape, or angle of a feature. • Basic dimensions are identified by enclosing the dimension in a box. • Basic dimensions specify theoretically exact value from which variations are defined through feature control frames as well as toleranced features and notes. • General tolerances do not apply to basic dimensions.