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What Is GD&T?


GD&T stands for Geometric Dimensioning and Tolerancing. It is a system of symbols, rules and definitions used to define the geometry of mechanical parts.

GD&T is one of the most powerful tools available that can improve quality, reduce cost and shorten delivery time. All of this is possible when the concurrent engineering team is involved with the creation of the drawing. The drawing is a common thread that ties these groups together. They all are involved with the engineering drawing. GD&T on the drawing must first and foremost capture design intent. However, the best design in the world is worthless if it cannot be produced. That is why it is necessary for production/vendors and quality to be involved with the requirements that are placed on the drawing. When they are not involved, the drawings often have overly tight tolerances and result in non-producible parts. At least not producible at the quality level, cost and timeliness expected by industry.

Nearly every company in the United States and many companies around the world use the ASME Y14.5 standard on GD&T. There is an ISO standard but it is in a state of flux. Because of this the Y14.5 standard is recognized and used around the world.

In short, GD&T is:

There is no other standardized way to control the geometry of parts. The old methods were never standardized. Many people thought they knew what the old method meant. The problem was that many people interpreted the drawing differently. GD&T is standardized and mathematized which means that anyone who knows the Standard, knows what the drawing means. GD&T is today's Print Reading. Anyone who creates, approves or uses the drawing should know how to read the drawing. In today's world, if you do not know GD&T, you do not know how to read!



  • "I've learned more in just a few hours with the Tec-Ease GD&T Hierarchy Coach than in 12 weeks taking a similar on-line program. I look forward to the time I get to spend viewing the presentations and taking the interactive quizzes. Here at FOX the Tec-Ease GD&T Hierarchy Coach is rated "best in class".
    - Marvin D.
  • "Thank you for all that you do. Your "Tips" are INVALUABLE -- I frequently refer to the archive for advice when I run across a sticky tolerancing puzzle."
    - Barbara P.
  • "I must say that I think you are the best GDT trainer/vendor of the many available. I have purchased your GDT charts, aids, and "The GDT Hierarchy" and found them to be clear and well illustrated."
    - Michael W.
  • "I absolutely love this course! (The GD&T Hierarchy Coach) I can go as slow as I want and go back and review slides if I need to. This is the way to go. I don't interrupt others learning, yet I get to fully understand before I move on."
    - Gwen M.
  • "Things are going well with our project. In less than a year we will be shipping a clinically significant, quality changing product to China from a US manufacturer. Cost competitive with great clinical outcome. I love the approach. I appreciate your help on this project. We have had a lot of feedback from our supply base saying great use of datum's and design for manufacturability."
    - Dave D.