GD & T

Geometric Dimensioning and Tolerancing (GD&T): is a language of symbols and standards designed and used by engineers and manufacturers to describe a product and facilitate communication between entities working together to manufacture product.

 Important GD&T basics and concepts:

  • CNC machining tolerances
  • The Datum Reference Frame (DRF)
  • Interpreting GD&T Symbols
  • Applying Geometric Symbols to Engineering Drawings
  • The Feature Control Frame
  • Communicating Basic Dimensions
  • Material Condition Modifiers

Tolerances in engineering are an allowable amount of variation of a physical dimension. It’s important to keep tolerances on engineering drawings in perspective.

GD&T is an entirely new way of describing the dimensions and tolerances compared to traditional plus/minus tolerancing. Fundamentally, the engineer designs a part with perfect geometry in CAD, but the produced part is never perfect. Proper use of GD&T can improve quality and reduce time and cost of delivery by providing a common language for expressing design intent.

The benefits of Geometric Dimensioning and Tolerancing (GD&T) are:

  • A standardized design language
  • A clear and precise way for the customers, suppliers, and production teams to communicate
  • A method for calculating the worst-case mating limits
  • Production and inspection processes are repeatable
  • Assembly is assured from qualified production parts