iii Preface G eometric Dimensioning and Tolerancing provides complete fundamentals of geometric dimensioning and tolerancing (GD&T) concepts as published in the American Society of Mechanical Engineers (ASME) standard ASME Y14.5-2018 Dimensioning and Tolerancing. This textbook refers to the standard as ASME Y14.5 or ASME Y14.5-2018. ASME Y14.5 specifies engineering drawing and related docu- mentation practices. Drawings based on ASME Y14.5 should have a general note that states: DIMENSIONING AND TOLERANCING PER ASME Y14.5-2018. Exam- ples in this textbook display two-dimensional (2D) drawing views in third-angle projection and three-dimensional (3D) models. Other ASME Y14.5 documents include ASME Y14.5.1M Mathematical Definition of Dimensioning and Tolerancing Principles and ASME Y14.5.2 Certification of Geometric Dimensioning and Tolerancing Professionals. The ASME Y14.41 Digital Product Definition Data Practices standard establishes required documentation practices for digital prod- uct definition. The ASME Y14.1 Decimal Inch Drawing Sheet Size and Format standard defines requirements for general dimensional tolerances found in the title block and in gen- eral notes for inch applications. The ASME Y14.1M Metric Drawing Sheet Size and For- mat standard applies to metric applications. The ASME Y14.35 Revision of Engineering Drawings and Associated Documents standard establishes recommended practices for engineering change applications. Other standards that relate to drafting practices include ASME Y14.3 Multiview and Sectional View Drawings and ASME Y14.100 Engi- neering Drawing Practices. The ASME headquarters is at Two Park Avenue, New York, NY 10016-5990. ASME standards can be ordered directly from ASME.