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GD&T GD&T ASME Y14.5-1994

GD&T is a symbolic language. It is used to specify the size, shape, form, orientation,and location of features on a part. Features toleranced with GD&T reflect the actual relationship between mating parts. Drawings with properly applied geometric tolerancing provide the best opportunity for uniform interpretation and cost-effective assembly. GD&T was created to insure the proper assembly of mating parts, to improve quality, and to reduce cost. GD&T is a design tool. Before designers can properly apply geometric tolerancing, they must carefully consider the fit and function of each feature of every part. GD&T, in effect, serves as a checklist to remind the designers to consider all aspects of each feature. Properly applied geometric tolerancing insures that every part will assemble every time. Geometric tolerancing allows the designers to specify the maximum available tolerance and, consequently, design the most economical parts.

GD&T communicates design intent. This tolerancing scheme identifies all applicable datums, which are reference surfaces, and the features being controlled to these datums. A properly toleranced drawing is not only a picture that communicates the size and shape of the part, but it also tells a story that explains the tolerance relationships between features.


  • Introduction to Geometric Dimensioning and Tolerancing
  • Basic Principles of GD&T
  • Dimensioning & Tolerancing Fundamentals
  • Symbols, Terms and Rules
  • Datum, Form and Orientation
  • Position, General
  • Position, Location
  • Position, Coaxiality
  • Concentricity and Symmetry
  • Runout
  • Profile
  • Graphic Analysis
  • A Strategy for Tolerancing Parts