Geometric Dimensioning

Geometric Dimensioning and Tolerancing by cademate

Geometric Dimensioning and Tolerancing (GD&T) is a system for defining and communicating engineering tolerances. It uses a symbolic language on engineering drawings and computer-generated three-dimensional solid models that explicitly describes nominal geometry and its allowable variation. It tells the manufacturing staff and machines what degree of accuracy and precision is needed on each controlled feature of the part. GD&T is used to define the nominal (theoretically perfect) geometry of parts and assemblies, to define the allowable variation in form and possible size of individual features, and to define the allowable variation between features.

• Dimensioning specifications define the nominal, as-modeled or as-intended geometry. One example is a basic dimension.
•  Tolerancing specifications define the allowable variation for the form and possibly the size of individual features, and the allowable variation in orientation and location between features. Two examples are linear dimensions and feature control frames using a datum reference (both shown above).

You will have to learn GD&T so as to precisely define nominal geometry of parts and assemblies. GD&T is widely used in automotive, aerospace, electronics, and commercial design and manufacturing industries. A mastery over the language of GD&T that consists of dimensions, tolerances, symbols, definitions, rules, and conventions has become an important skill for engineers, designers and other CAD users

GD&T training is included in almost all courses that are offered by CADEMATE for engineers. The GD&T module will impart you a thorough understanding of the following aspects: 

• Dimensioning specifications: To define the nominal, as-modeled or as-intended geometry of parts

• Tolerancing specifications: To define the allowable variation for the form and possibly the size of individual features and allowable variation in orientation and location between features.
  
• Geometric characteristics: Designers can use symbolic language on engineering drawings and computer generated 3D solid models to explicitly describe nominal geometry and its allowable variations.
• The geometric symbols include straightness, flatness, circularity, and cyclindricity, profile of a line, surface, perpendicularity, and angularity.