Basic Concepts of Geometric Dimensioning and Tolerancing

Geometric Dimensioning and Tolerancing (GD&T) is an international and exact language that enables the designers to "say what they mean" on a drawing. It consists of a well-defined set of symbols, rules, definitions, and conventions that can be used to describe the size, form, and orientation and location tolerances of part features. It is a precise language & must be used precisely. Reference datums are critical & symbols must be used in precise order. Many errors can occur when inexperienced designers try out GD&T. This article Is intended to stress the need for gaining more knowledge in the area of GD&T. Many technical personnel and managers in particular are finding difficult to understand and use the drawing coming across their desks. Perhaps they need to know more about the various aspects of the GD&T representations used in the engineering drawings such as fundamental dimensioning rules, basic tolerancing concepts, geometric tolerancing symbols, definitions and representations, positional tolerancing, reference datum, definition and usage of material condition modifiers, etc.