Dimensioning and tolerancing must be fully specified so there is a complete understanding of every feature's requirements.
Unless otherwise specified, the limits of size of an individual feature of size control both the size and the form (shape) of that feature.
The standard relies on several fundamental rules that guide how dimensions and tolerances are applied: Dimensioning and Tolerancing ASME Y14.5M-1994
Modifiers like Maximum Material Condition (MMC) allow for "bonus tolerance" as the part’s actual size deviates from its limit, providing flexibility for manufacturing without sacrificing assembly. Y14.5M-1994 - Dimensioning and Tolerancing - ANSI Webstore
is a foundational standard for Geometric Dimensioning and Tolerancing (GD&T) used in mechanical engineering to ensure parts are designed and manufactured with precise functional requirements. It establishes a universal symbolic language to describe a part's geometry and allowable variations, reducing ambiguity in technical drawings. Core Principles and Fundamental Rules Dimensioning and tolerancing must be fully specified so
The standard organizes geometric controls into several functional categories to manage different aspects of part geometry: Typical Controls Straightness, Flatness, Circularity, Cylindricity
Controls the physical placement of features relative to each other or a datum. Profile of a Surface, Profile of a Line Controls the boundary of a feature's outline. Runout Circular Runout, Total Runout Controls variation in a surface when rotated about an axis. Building Blocks of the Language Profile of a Surface, Profile of a Line
Controls the shape of a feature regardless of its location or orientation. Parallelism, Perpendicularity, Angularity Controls the rotation of a feature relative to a datum. Location Position, Concentricity, Symmetry