What is Geometric Dimensioning and Tolerancing?

Geometric Dimensioning and Tolerancing (GD&T) is a symbolic language used in engineering and manufacturing to communicate and control the dimensions and tolerances of geometric features on a part or product. It ensures that the parts are manufactured and assembled with precision, leading to better interchangeability, functionality, and quality.

The GD&T system uses a set of symbols, rules, and definitions to specify the allowable variation in form, size, orientation, and location of features on a part. It provides a more comprehensive and precise way of expressing design requirements compared to traditional linear dimensioning.

The basic components of GD&T include:

Geometric Features: These are specific shapes or elements on a part, such as lines, circles, cylinders, and surfaces.

Tolerances: GD&T defines allowable variations or tolerances for each geometric feature. Tolerances can be expressed in various ways, such as ±0.1 mm, or using more specific symbols and modifiers.

Datum: A datum is a theoretically perfect feature used as a reference for establishing the location and orientation of other features.

Symbolic Language: GD&T uses specific symbols, letters, and numbers to represent geometric control information. Some common symbols include position, concentricity, flatness, parallelism, perpendicularity, etc.