Tolerancing Optimization Strategies
Gregory A. Hetland, Ph.D.
Hutchinson Technology Inc.
Dr. Hetland is the manager of corporate standards and measurement sciences at Hutchinson Technol-
ogy Inc. With more than 25 years of industrial experience, he is actively involved with national, interna-
tional, and industrial standards research and development efforts in the areas of global tolerancing of
mechanical parts and supporting metrology. Dr. Hetland’s research has focused on “tolerancing opti-
mization strategies and methods analysis in a sub-micrometer regime.”
This chapter will give a few examples to show the technical advantages of transitioning from linear
dimensioning and tolerancing methodologies to geometric dimensioning and tolerancing methodologies.
The key hypothesis is that geometric dimensioning and tolerancing strategies are far superior for clearly
and unambiguously representing design intent, as well as allow the greatest amount of tolerance.
Geometric definitions can have only one clear technical interpretation. If there is more than one
interpretation of a technical requirement, it causes problems not only at the design level, but also through
manufacturing and quality. This problem not only adds confusion within an organization, but also ad-
versely affects the supplier and customer base. This is not to say that utilization of geometric dimension-
ing and tolerancing will always make the drawing clear, because any language not used correctly can be
misunderstood and can reflect design intent poorly.
Tolerancing Progression (Example #1)
Figs. 3-1 to 3-3 show three different dimensioning and tolerancing strategies that are “intended” to reflect
designer’s intent, and the supporting figures are intended to show the degree of variation allowed by the
defined strategy. These three strategies reflect a progression of attempts to accomplish this goal.
3-2 Chapter Three
Fig. 3-3 depicts the optimum dimensioning and tolerancing stra