MIL-STD-8 was published in 1949, and was revised in 1953 to include GD&T “Rule 1.” Then in 1957, the American Society of Mechanical Engineers (ASME) published their first standard incorporating GD&T, ASA Y14.5. The first standards for GD&T were developed by the US military in the 1940s. Parker published the first work on GD&T in 1940, titled, “Notes on Design and Inspection of Mass Production Engineering Work.” He published another title in 1956, “Drawings and Dimensions.” Parker developed the concept of “ True Position” and is credited with being the originator of GD&T. He went on to develop tolerancing practices to address the functional requirements of a part. Parker realized that there were parts that met functional requirements that were being rejected due to out of tolerance measurements. How did GD&T come about? Near the beginning of World War II, a man named Stanley Parker was working at the Royal Torpedo Factory in Alexandria, West Dunbartonshire, Scotland. Using GD&T results in a more accurate design, larger tolerances for less important design features, and cost savings for manufacturing. Geometric Dimensioning and Tolerancing is a set of rules and GD&T symbols used on a drawing to communicate the intent of a design, focusing on the function of the part. What is GD&T? If you are involved in design or manufacturing, you may be familiar with the term, “GD&T,” or “Geometric Dimensioning and Tolerancing”.
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