Intro to Geometric Dimensioning and Tolerancing

We are going to review Geometric Dimensioning and Tolerancing¬† (GD&T) and what it is, why it’s important, and how we use it today. GD&T really began after World War II when the US fabricated parts to specifications, but did not successfully assemble. This created major issues especially since it was during a very critical time. Prior to GD&T, there was conventional tolerating methods that were used, but were not very accurate or reliable. After WWII, a committee investigated many of the defective parts as to why they were not accurately made to assemble if the parts were made to their specifications. They found the parts varied in dimension which caused the parts to be out of spec for assembly. As a result, the committee developed GD&T which allowed for a certain degree of variation of a dimension (tolerance) in order for parts to remain within its specification, properly assemble to mating parts, improve quality, and to essentially reduce cost. This great finding reached other industries other than the government sector, and companies and institutions began adopting the use of tolerances. Since then, new industry standards have been created and are regularly used in today’s manufacturing. Continue reading