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Chapter 14
A. Geometric Dimensioning and
Tolerancing (GD&T)
Contributed by
Dr. Nabeel Yousef, University of Central Florida—Orlando
Part III.A.1
INTRODUCTION
Geometric dimensioning and tolerancing (GD&T) is defined as the language of
symbols used in mechanical drawing to efficiently and accurately communicate
geometry requirements for features on parts and assemblies (ASME 1994). GD&T
is used in a wide variety of manufacturing industries on the national and international
level. GD&T is used to ensure successful and accurate communication
between the design department and the production department. GD&T is the language
that enables design engineers to express what they mean on a drawing,
thus improving product designs and lowering cost. Process engineers and manufacturing
use the language to interpret the design intent and to determine the best
manufacturing approach. Quality control and inspection use the GD&T language
to determine proper setup and part verification (ASME 1994).
Understanding how to implement and translate GD&T drawings will aid in
improving product design and effectively communicate design requirements for
suppliers and manufacturing (Gunderson 1994).
1. BLUEPRINTS AND ENGINEERING DRAWINGS
Define and interpret various sections of
technical drawings, including title, tolerance,
and revision blocks, notes, scale, etc.
(Application)
Body of Knowledge III.A.1
An engineering drawing is a type of drawing that is technical in nature, used to
fully and clearly define requirements for engineered items. The purpose of engineering
drawings is to accurately and clearly capture all the geometric features of
a product or a component that will convey the required information for the production
team.
Engineering drawings are often referred to as blueprints, a name that reflects
the way those prints were originally made using chemical material to print blue
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