Module 1

TRAINING DURATION: 2 days (16 h).
PREREQUISITE: Basic knowledge in blueprint reading.

« GD&T » is an acronym for “Geometric Dimensioning and Tolerancing.” It is defined in standard “ASME Y14.5” and maintained by the American Society of Mechanical Engineers.

Because dimensional tolerances apply independently one from another, with no reference system to control the variations between features, it is difficult or even impossible to evaluate with accuracy the final form of the parts, or the interaction between parts at assembly.

GD&T was initially developed to address this problem. It introduces the concept of 3D reference systems in the 2D drawing (the Datum Reference Frame), and symbols to control the position and orientation of geometric features in a 3D system.

However, GD&T applied by poorly trained personnel can create bigger problems than not using GD&T at all.

Poorly applied GD&T often result in:

  • Functional parts that are rejected at inspection.
  • Non-functional parts (do not fit at assembly) accepted at inspection.
  • Cost of parts that increase when using GD&T.
  • High non-quality costs.
  • Difficulty to find suppliers.
  • Etc.

The objective of Module 1 is to learn the GD&T tolerancing system as defined by applicable standards.

  • Introduction and historical overview of GD&T.
  • Basic principles of GD&T and GPS (Geometric Product Specification – ISO).
  • Review of basic symbols review (ex.: diameter, depth, counterbore, countersink, chamfer, …).
  • In-depth review of the main modifiers (MMC, LMC, P, F, ST, …).
  • The Datum Reference Frame.
  • The concept of Degrees Of Freedom (DOF), datum targets, etc.).
  • Interpretation and application of Geometric Tolerances of Form.
  • Interpretation and application Geometric Tolerances of Profile.
  • Interpretation and application Geometric Tolerances of Localisation.
  • Interpretation and application Geometric Tolerances of  Orientation.
  • Interpretation and application Geometric Tolerances of  Runout.
  • Exercises.

All personnel that, in the course of their work, have to read and interpret drawings with GD&T, like technicians, engineers, inspectors, buyers of mechanical parts, and others.