Geometric Dimensioning and Tolerancing (GD&T)

ASME Geometric Dimensioning and Tolerancing Training
ASME Y14.5M-1994, ASME Y14.5.1M-1994, ASME Y14.5-2009, ASME Y14.8-2009, ASME Y14.41-2003, ASME Y14.41-2012
ASME GD&T Training

ISO Geometrical Dimensioning and Tolerancing Training
ISO 1101, ISO 286-1, ISO 286-2, ISO 1660, ISO 2692, ISO 2768-1, ISO 2768-2, ISO 5858, ISO 5459, ISO 8015, ISO 14405-1, ISO 14405-2, ISO 14660-1, ISO 14660-2, etc.
ISO GD&T Training

GD&T Training Slide 2015 - 150

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Geometric Dimensioning and Tolerancing (GD&T) [ASME] and Geometrical Dimensioning and Tolerancing (GD&T) [ISO] has been used since the 1940s.. The need to define ever more complex part geometry and the need to guarantee interchangeability of parts has contributed to its widespread use. Today, it can be found in nearly all manufacturing industries, from the very small geometry found in integrated circuits and electronic components to the very large geometry found on rockets, the now-retired space shuttle, and the international space station. The importance and value of GD&T is apparent in all manufactured products, regardless of the physical size of the product. If your goal is to clearly define the geometric requirements for a physical component or product, then you must use GD&T.

GD&T has found its greatest application in mass production, where interchangeability of blindly selected parts is essential. Without GD&T and tolerance analysis, there is no way to know that parts have been designed such that all manufactured parts will fit together at assembly. This is becoming more critical today due to ever more powerful design tools and more restrictive business practices.

Design engineers have become adept and power users of 3D solid modeling software; although they are incredibly powerful design tools, 3D solid modeling systems may provide a false sense of adequacy, perhaps even a bit seductive in how perfectly the design is depicted. The models on the screen are perfect; all parts fit together, and the perfect design can be analyzed carefully to verify performance. However, we will never see perfect parts like those shown in the CAD system. The assembler will assemble imperfect parts, and only through the proper application of GD&T and tolerance analysis can the design engineer know that the parts will be interchangeable. Just-in-time manufacturing increases the demand for parts that absolutely must fit at assembly, as it is much less likely today to have spare parts waiting in the warehouse. Parts simply must fit together at assembly. Advanced Dimensional Management’s GD&T and Tolerance Analysis training courses and reference materials are coordinated so you can achieve this higher level of understanding, so you can design interchangeable parts.

GD&T is equally beneficial in R&D and one-of-a-kind components and assemblies, as there is no other way to ensure that the allowable variation of part geometry is adequately defined. Indeed, that is the point – to define the relationship between geometric features on a part to ensure the part will work. Whether it is the form of the surface of a cam, the coaxial relationship between the head of a bolt and the thread, the location of a pattern of holes, or the location of a bracket in an assembly, GD&T is absolutely the best way to define the variation allowed between part features.

GD&T Training

In our GD&T training and GD&T courses we teach the concepts, rules and language of GD&T. We teach GD&T from a functional viewpoint, discussing the topics from the point-of-view of application to real world problems. Functional Dimensioning and Tolerancing is what we are all about.

We offer Level 1, Level 2, Level 3 and Custom GD&T training and GD&T courses. We also offer Functional Dimensioning and Tolerancing courses and GD&T Certification Preparation workshops and seminars. Our GD&T training may be based on ASME standards (ASME Y14.5M-1994, Y14.5-2009) or on ISO standards (ISO 1101, ISO 5459, etc.). All of our GD&T and Tolerance Analysis courses are coordinated, as our goal is for your staff to design such that geometric problems are not built into your products, your manufacturing and inspection staff clearly understands the geometric requirements, and your assembly and service personnel are provided parts that fit together and are interchangeable. The language of GD&T and tolerance analysis methods are needed to achieve these goals. We teach GD&T from a very legalistic point of view. In fact, all of our courses are taught from a legal point of view. Engineering drawings and annotated models are legal documents and form part of a contract between client and supplier. It is essential that the correct specifications are developed, and that all parties involved understand the requirements contained in those specifications. We take GD&T seriously. We take your time seriously. We take your success seriously.

Basic GD&T Training - Rigorous and Relevant

Level 1 GD&T courses the fine details of GD&T and system of GD&T as a coherent whole. We address on the meaning of the symbols and specifications, how to properly specify plus and minus and GD&T, explain the limitation of plus and minus and how GD&T eliminates these limitations, and how these details work together in a full system. We explain the exact meaning of all the Geometric Tolerances, Definitions, the Fundamental Rules, Feature Control Frames and Datum Reference Frames. Functional Dimensioning and Tolerancing concepts are introduced and woven through the curriculum. Dimensional management principles are introduced as well. Context is king in GD&T, and we make it very clear how all of the GD&T details work in context. GD&T – In Context™ - it’s another method pioneered by Advanced Dimensional Management LLC to guarantee you get theunderstanding you need.

Applications-Based and Advanced GD&T Training

Level 2 GD&T with Applications and Level 3 GD&T courses are taught with the requirements of the final product in mind, which includes the effect of the GD&T on Tolerance Stackups. Extended Dimensional Management concepts are introduced. We want our clients to understand the implications of the tolerances they specify, including the functional implications and the cost implications of the assembly, manufacturing and inspection processes. The many nuances of GD&T and the importance of syntax and context are discussed in detail. Functional Dimensioning and Tolerancing concepts are further developed and explained throughout the courses. Many exercises are included in these courses.

Customized GD&T Training

If desired, our GD&T training and GD&T courses may be customized around your products and problems. Custom courses can be anything you want. Our GD&T training has been successful in a variety of environments and contexts.

What’s in a Name? GD&T
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 Y14.5subcommittee. 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 Training Programs, please click here.

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