Geometric Dimensioning and Tolerancing or Geometrical Dimensioning and Tolerancing?

There are two systems, versions, or flavors of GD&T. The first version was released in North America and is called Geometric Dimensioning and Tolerancing (GD&T). This version of GD&T is developed and maintained by ASME, specifically their Y14.5 subcommittee. The ASME GD&T system is used throughout the world, but it is the primary GD&T standard in North America. Many multi-national corporations use ASME Y14.5 (ASME Y14.5M-1994 or ASME Y14.5-2009) as their GD&T standard worldwide for all of their international operations. The International Organization for Standardization (ISO) also has a version of GD&T, which they call Geometrical Dimensioning and Tolerancing (GD&T). The ISO GD&T standard is part of the Global Product Specification (GPS) series of standards produced by ISO technical committee TC213. Note that there are many standards that make up the ISO GPS system. Some ISO dimensioning standards are developed by a different ISO technical committee, ISO TC10. In the ASME system, there is essentially one dimensioning and tolerancing standard, ASME Y14.5-2009, accompanied by perhaps 8 other core standards needed for line types, lettering, modeling and related techniques. In the ISO system there are scores of standards for dimensioning and tolerancing, and scores more for modeling and related techniques. There are differences between the ASME and ISO systems; some differences are visually apparent, and other differences are much more subtle. We are experts and active in the development of both systems. Contact us for help with either system or to better understand the differences between the systems. These differences are becoming more critical as we move to an ever-more global supply chain.

Although GD&T is a science of the details, it must also be understood in the context of the big picture. We also explore the implications of Dimensioning and Tolerancing Schemes outside of design, on the rest of our clients’ companies and supply chain, helping them to understand the tradeoffs in cost and quality they make when selecting various Tolerancing Schemes. We bring dimensional management strategies into your company and help you manage variation between departments, divisions, between internal and external organizations, and across the supply chain.

Bryan R. Fischer, President of Advanced Dimensional Management LLC is an ASME Certified Senior Level GD&T Professional, a support group member of the ASME Y14.5 standards sub-committee responsible for GD&T and Dimensioning and Tolerancing in the United States, and works with several ISO committees working on dimensioning and tolerancing and GD&T. He is a member of ISO TC184/SC4 and actively involved in development and implementation of ISO data modeling and ISO GPS standards. He is actively involved with the development of the next generation of these important standards and recognized as one of the leading experts in this field. Bryan has written, published, and edited many books on GD&T, Tolerance Analysis and related subjects.

GD&T Certification and Testing Information

ASME offers technology and engineering professionals the opportunity to prove their knowledge of ASME Y14.5M-1994 by taking either a Technologist Level or Senior Level Exam. The Technologist Level Exam is designed to test your understanding of the content of the standard; the Senior Level Exam is designed to test your understanding of the content of the standard, and application of its principles.

Advanced Dimensional Management training and materials can help prepare your staff to take ASME’s GD&T Certification tests. Please contact us if you would like more information

For a link to information about ASME’s GD&T Professional Certification Examinations and related