Use the GD&T Symbols Reference & Feature Control

What is the GD&T Symbols Reference & Feature Control?

Geometric dimensioning and tolerancing (GD&T) is the symbolic language engineers use to control the form, orientation, location and runout of features on a drawing. This reference lists the 14 characteristic symbols — straightness, flatness, circularity, cylindricity, profile of a line, profile of a surface, perpendicularity, angularity, parallelism, position, concentricity, symmetry, circular runout and total runout — each drawn as a clean vector icon with its category, whether a datum is required, the shape of its tolerance zone, what it controls and a typical use, with search and category filters. The standards differ slightly: ASME Y14.5-2018 removed concentricity and symmetry, ISO 1101 keeps them, and the page says so.

The feature control frame builder lets you choose a characteristic, a cylindrical or spherical zone, a tolerance value, a material condition modifier (MMC or LMC) and up to three datums, shows the frame as you would draw it, explains it in plain English, flags mistakes such as a missing datum on a perpendicularity tolerance, and lets you copy it as text or download it as an SVG. A third tab explains modifiers and datum symbols: MMC, LMC, RFS, projected zone, free state, tangent plane, diameter, basic dimensions and datum targets.