Copyright Goodheart-Willcox Co., Inc. 1 L E A R N I N G O B J E C T I V E S After studying this chapter, you will be able to: Explain how dimensioning and tolerancing applies to engineering drawings and models. Identify and explain the benefits of geometric dimensioning and tolerancing (GD&T). Describe the history and evolution of engineering drawings and GD&T. List common design and drawing standards and explain the importance of standards. Describe the differences between coordinate tolerancing and geometric tolerancing. Explain methods for defining coordinate systems, the origin of dimensions, and tolerance zones. Describe the purpose of computer-aided design and drafting (CADD). Explain how designers and drafters apply GD&T to engineering drawings and models. Explain how GD&T applies to computer-aided manufacturing (CAM). T E C H N I C A L T E R M S 2D drawing 3D annotation 3D model annotated model basic dimension bilateral tolerance Cartesian coordinate system chain dimensioning code computer-aided design and drafting (CADD) computer-aided design and drafting/computer- aided manufacturing (CADD/CAM) computer-aided manufacturing (CAM) computer numerical control (CNC) coordinate tolerancing datum datum feature datum feature simulator descriptive geometry digital product definition (DPD) dimension dimensioning directly toleranced dimension drafter engineering drafting feature control frame (FCF) first-angle projection geometric dimensioning and tolerancing (GD&T) geometric tolerancing interchangeability limited dimension drawing (LDD) maximum material condition (MMC) mechanical computer- aided design (MCAD) mechanical drafting model-based definition (MBD) multiview drawing orthographic projection parallelism positional tolerance product and manufacturing information (PMI) product definition data set rectangular coordinate system simulated datum solid model specified dimension standard surface model third-angle projection tolerance tolerance accumulation tolerance buildup tolerance stacking true geometric counterpart true position Geometric Dimensioning and Tolerancing Essentials C H A P T E R 1