ASME Y14.5-2018

The Y14.5 standard is considered the authoritative guideline for the design language of geometric dimensioning and tolerancing (GD&T.) It establishes symbols, rules, definitions, requirements, defaults, and recommended practices for stating and interpreting GD&T and related requirements for use on engineering drawings, models defined in digital data files, and in related documents.
GD&T is an essential tool for communicating design intent — that parts from technical drawings have the desired form, fit, function and interchangeability. By providing uniformity in drawing specifications and interpretation, GD&T reduces guesswork throughout the manufacturing process — improving quality, lowering costs, and shortening deliveries.
Now, a consensus committee of experts has revised Y14.5 for 21st-century applications. Because of the widespread use of computer-aided design (CAD) and the industry transition toward reduced use of
orthographic views for product definition, model views were added in many figures throughout the Standard. This revision also emphasizes the use of profile for location tolerances applied to surfaces.
Important changes include: concept of feature of size; datum references and degrees of freedom; composite position tolerances; surface boundaries and axis methods of interpretation; profile tolerances; and symbology and modifiers tools. Additionally, the subject matter has been restructured for better readability, with profile, orientation, and form now in separate sections, and material within sections reorganized.
ASME Y14.5-2018 is a replacement of ASME Y14.5-2009.