Geometric Dimensioning & Tolerancing (GD&T) overview

In order to develop a method of effective communication, standards have been put into place related to the practice of GD&T. In North America, ASME Y14.5-2009 (most updated version) is the most commonly used standard, while ISO 1101 is more prevalent in Europe. Regardless of the industry, it is common for users to outsource GD&T applications due to the ease of implementation and retrieval of accurate part data.

What is GD&T?

Geometric Dimensioning & Tolerancing (GD&T) is a language representative of engineering drawings to classify deviations and tolerance of part measurements and geometric analysis. It is an efficient way of communicating measurement conditions and specification of a part. Consisting of symbols, this language is used to define the allowable variations subject to theoretically ideal or perfect geometry.

What is the purpose of GD&T?

A language developed to assist with the understanding of dimensional requirements, GD&T can be utilized effectively in the following areas:

  • Detail the engineering specifications and requirements of a part
  • Assist in ensuring that the part is developed in the anticipated form
  • Able to improve quality and reduce costs of produced parts

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What are the benefits of GD&T?

Implementing GD&T within the manufacturing and inspection process has many benefits, including:

Replaces details described in drawings of complex geometry components with symbolic language, to precisely describe manufacturing design and inspection conditions

Is a standard utilized across the world that increases the ability to communicate design specifications

Flawlessly defines the engineering intent of parts

When is GD&T required?

GD&T should be implemented when the design specifications of a part are critical to its function or consists of complex geometry. GD&T is commonly implemented when a manufacturer is simply looking to ease the process of defining and evaluating part tolerances. When a common origin reference point is to be determined, a GD&T is useful in defining such requirements.


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