4 GD&T: Application and Interpretation
Copyright Goodheart-Willcox Co., Inc.
Color is used to separate explanation data
from the main portion of the fi gures. Color is also
used to highlight instructional information such
as tolerance placement requirements and tolerance
zone boundaries.
Interpretation fi gures are provided to show
the tolerance zones resulting from tolerance speci-
fi cations. Tolerance zones and part variations in
these fi gures are suffi ciently exaggerated to make
them visible.
Uppercase letters are used for notations that
are part of the drawing. Lowercase letters are
used for instructional notes and information. One
exception is that degrees of freedom notations,
within a drawing, are made with lowercase letters
as required by the ASME standards.
Dimensioning and tolerancing of a part
requires application of principles from the ASME
Y14.5 standard. When defi ning tolerances in digi-
tally defi ned products (using CAD), conformance
with ASME Y14.41 is desirable. GD&T: Application
and Interpretation shows how to apply the prin-
ciples in these standards to many situations and
offers suggestions regarding the extension of the
principles to situations not shown in the stan-
dards. Care must be taken in the extension of prin-
ciples. Otherwise, a violation of the standards or
unclear requirements could result. Compliance
with the standards is ultimately the responsibility
of the person applying or interpreting dimensions
and tolerances.
About the Author
Bruce A. Wilson, author and illustrator
of GD&T: Application and Interpretation, has an
international reputation as a leader in Dimen-
sional Management and Geometric Dimension-
ing and Tolerancing (GD&T). He is certifi ed by the
American Society of Mechanical Engineers (ASME)
as a Senior Level Geometric Dimensioning and
Tolerancing Professional. He has more than 25
years participation in ASME subcommittee Y14.5
standards development. He served as the leader
of the positional tolerances section of the standard
for more than 14 years and now is chairman of the
Y14.5 subcommittee.
Mr. Wilson has extensive training and con-
sulting experience. He has industrial and aca-
demic experiences that provide the expertise and
practical knowledge necessary to write a dimen-
sioning and tolerancing text that is technically
correct and applicable to today’s industrial needs.
Mr. Wilson has taught GD&T in Europe and
the United States. His experience includes cur-
riculum development, teaching, management of
training programs, and instructor development.
Areas of concentration include Dimensioning and
Tolerancing for engineering and manufacturing,
Computer-Aided Design, Dimensional Manage-
ment, and New Designer Training. Mr. Wilson led
training programs for thousands of design engi-
neers, manufacturing engineers, machinists, tool
designers, tool makers, quality engineers, inspec-
tors, supplier managers, and managers. He has
advised executives regarding the technical needs
and health of their organizations.
Mr. Wilson’s industrial experience includes
responsibilities ranging from design engineer
to program manager and industrial consultant.
He was recognized as a Technical Fellow in The
Boeing Company. His design engineering experi-
ence includes precision mechanisms, electrome-
chanical, optics packaging, electronics packaging,
pneumatics, and aircraft structures. His experi-
ence has taken place in companies ranging from 20
to 170,000 employees, producing everything from
bicycle wheels to spacecraft.
Mr. Wilson’s extensive design experience has
provided a thorough exposure to dimensioning
and tolerancing requirements as they apply to
various applications. He is an industrial leader in
the discipline of dimensional management. He led
teams to establish product system requirements,
complete 3D variation analysis, apply tolerances to
detail parts and assemblies, communicate require-
ments to production, defi ne locating methods for
major assemblies, and implement quality assur-
ance measures related to dimensional variation.
His variation analyses and assembly concepts
have resulted in product cost savings greater than
50% and elimination of assembly tooling costs for
major aircraft structure. The processes he explored
are now implemented widely. Mr. Wilson has mul-
tiple United States patents for calculation methods
used to assess variation effects.
Senior