Major Rules of GD&T 311

Major Rules of GD&T provides an overview of the rules and concepts of geometric dimensioning and tolerancing, or GD&T. The major rules include Rule #1, or the Envelope Principle, which specifies how size controls form, Rule #2, or RFS and RMB defaults, and the 3-2-1 Rule, which defines the minimum number of points of contact in the datum reference frame. In addition to these major rules, other concepts described are bonus tolerances, virtual and resultant conditions, and the components of the datum reference frame. GD&T functions as a complex language used in blueprints to convey necessary information about a part. GD&T standards offer specific guidelines for part features, including projected tolerance zones, radii, controlled radii, tapers, threads, and gears. To accurately read a GD&T print, users must understand its many rules and principles. After taking this class, users should be able to explain key GD&T concepts and approaches for part inspection.