vii New to This Edition T he text has been extensively revised to cover changes in the ASME Y14.5-2018 stan- dard. The new edition also features new content and expanded coverage through- out the text. A new chapter, Geometric Dimensioning and Tolerancing Essentials, provides an introduction to GD&T and related applications in design and engineering. In many illustrations throughout the text, 3D model views have been added to clarify details and aid in visualization. The following is a summary of changes and new features in this edition. • Enhanced introduction to dimensioning and tolerancing and GD&T. • Overview of how dimensioning and tolerancing is applied to 2D engineering drawings and 3D models. • In-depth discussions explaining the benefits of GD&T. • Information about the history and evolution of engineering drawings, industry standards, and GD&T. • Clarification of directly toleranced coordinate dimensioning. • Comparison between locating a part using the rectangular coordinate system and using datums to establish a reference coordinate system. • Explanation of methods for defining the origin of dimensions, establishing tolerance zones, and using geometric tolerancing to overcome tolerance buildup. • Expanded coverage on applying GD&T with CADD and using model-based definition software. • Additional content explaining how GD&T applies to CAM. • Expanded illustrations containing orthographic views, 3D model views, and detailed explanations of the content. • Updated coverage related to the datum reference frame concept. • Expanded coverage on degrees of freedom and constraints. • Expanded coverage on datum target applications. • Additional content, examples, and calculations related to MMC, LMC, RFS, MMB, LMB, and RMB. • Additional content clarifying movable datum targets, datum target points, and spherical datum target areas. • Additional content comparing RFS, MMC, and LMC applications. • Additional material boundary calculation examples. • Revised content related to restrained condition and tolerance applicability in the free state. • Expanded coverage on virtual condition and resultant condition with calculations and examples. • New content explaining how to verify the position of a feature using location measurements. • Noted explanations that specifications of concentricity and symmetry tolerances are not defined in ASME Y14.5-2018. • Revised content related to applying a nonuniform profile tolerance. • New content related to applying a dynamic profile tolerance.