Introduction to Geometric Dimensioning and Tolerancing (GD&T)
Session 1: What do all those letters, numbers, and symbols mean? GD&T Basics
A basic introduction to GD&T for someone with no previous experience with GD&T. Why do we use GD&T at all? What are the various symbols? What does that rectangular box of symbols and numbers on a drawing really mean? How do we inspect these rectangular boxes? Why do drawings have A, B, and C that are called datum planes? Can’t we just measure dimensions any way we choose? What does that M with a circle around it mean and why do we use it? What is a functional gage and why do we really want to inspect our parts with it?
Session 2: Nothing is Perfectly Round & Nothing is Perfectly Flat! Form and Orientation Tolerances
An introduction to form and orientation tolerances such as flatness, roundness (circularity), cylindricity, perpendicularity and parallelism. Each of the form and orientation tolerances are described and discussed regarding the feature control frame, the tolerance zone, and inspection. In many cases, these tolerances can be applied instead of defining very tight ordinary tolerances that are difficult to satisfy. Specifying a generous coordinate tolerance with a flatness geometric tolerance is often preferable to specifying a very tight coordinate tolerance that accomplishes the same condition.
Session 3: Position, Runout, and Go/No-Go Gauges
An introduction to position tolerances, the design of functional gages, and circular and total runout. Position tolerances are among the most used GD&T options and maybe the most complicated to understand. When used with the Maximum Material Condition (MMC), position tolerances allow the use of a functional gage to make inspection much easier to accomplish. Circular and total runout are tolerances very close in application to circularity and cylindricity but with one major difference that makes their use on rotating equipment necessary.