International Institute of
Geometric Dimensioning & Tolerancing
October 2009   Edition 2009.3

GD&T Seminar Series

GD&T Seminars
GD&T Seminar Series, click here for Seminar Home page

IIGDT has developed a multi-step Geometric Dimensioning and Tolerancing Seminar Series built upon years of proven experience in training new users in the fundamental to advanced topics of GD&T. Whether you are new, or an experienced user of GD&T, there is a Seminar level designed for you.

Click here to visit the GD&T Seminar home page 

The precision language of profile tolerancing is explicitly defined in the ASME Y14.5M-1994 Standard on Dimensioning and Tolerancing, and is mathematically complimented by the ASME Y14.5.1M-1994 Standard on Mathematical Definition of Dimensioning and Tolerancing Principles. Both of these Standards form the basis for precise definition of complex surface boundaries and should be the basis for 3D tolerance analysis for designers and also for 3D precision measurement analysis for physical metrologists.

3D Engineering Drawing Example
per ASME Y14.41-2003
GDT Example Drawing 
Complex Surface Analysis using
SmartProfileTM Software
GDT Example 
Criteria for Precision Measurement

Precision measurement requires high confidence that the measured results reflect differences between parts and not differences due to errors of measurement. IIGDT Seminars accomplish this, by demonstrating to the metrologist the following:

  1. Clear definition of the specification requirements per ASME Y14.5M-1994 or applicable standard.

    1. 3D surface geometries to be defined using profile tolerancing.
    2. 3D axes control to be defined using position tolerancing.
  2. Qualified metrologists perform the required tasks at a sufficient level utilizing the proper measurement instruments, sensors, procedures and software.
    1. This knowledge base must start with a clear understanding of the applicable standards and be solidified with high competency in precision measurement, including in-depth knowledge on the measurement instruments, sensors, procedures, analytical software and statistical analysis methods.
  3. Precise measurement instrument capable of measuring the feature.
    1. Placed in an environment conducive to the level of precision measurement required.
    2. 3D Parts require 3D measurement unless otherwise defined per engineering specifications. Anything less should be considered a rough check and does not have the ability to ensure full compliance to stated engineering requirements.
  4. Sound measurement procedure that will ensure true characterization of the feature.
    1. Holding fixture and devices as defined per the engineering specifications.
    2. Sufficient point densities to ensure positive characterization of the feature. Point densities are critical to characterizing the total manufacturing variation, and it is insufficient to take minimal points if the metrologist does not have previous knowledge of the part or process to justify a reduction in points taken on the surface.
  5. Robust measurement software capable of completing the analysis per the defined standards such as ASME Y14.5M-1994 and ASME Y14.5.1M-1994 or other applicable standards.
    1. Software such as SmartProfileTM developed by Kotem Technologies that defaults to the ASME Y14.5.1 Standard. This software has been extensively tested with mathematically defined datasets for Profile and Position Tolerancing with and without datums and fully invoking the rule of simultaneity.
    2. A word of caution: The majority of coordinate measuring machines (CMM) software used in all industries currently default to using least-squares fitting algorithms, which simply means they are averaging the measured results.
  6. Proper analytical methods for evaluating the uncertainty of the measured results. ASME B89.7.3.2 technical report provides Guidelines for the Evaluation of Dimensional Measurement Uncertainty and is a simplified guide for metrologists to evaluate all the contributing factors that influence the measured result.  
IIGDT Seminars
IIGDT offers 4 levels of training courses to suite your business requirements. These are:
Level 1 Blueprint Reading 
Level 2 Precision GD&T:
Introduction & Fundamental Principles  
Level 3  Precision GD&T:
Advanced Applications & Analysis  
Level 4  Applied Dimensional Metrology  
 A complete overview can be found here.
GD&T Chart:
Bring some of the classroom into your inspection room. The GD&T Chart provides guidance and examples to view everyday, click here:
GD&T Font Order Form

Upcoming Seminars:

October 12-13
Optical Gaging Products
Wilsonville, OR

October 15-16
Productivity Quality Inc.
Plymouth, MN

October 19-20
Optical Gaging Products
Santa Clara, CA

October 22-23
Optical Gaging Products
Ambler, PA

October 26-27
Optical Gaging Products
Salt Lake City, UT

October 29-30
Optical Gaging Products
St Louis, MO

November 2-6
University of Minnesota
St Paul, MN

To see our complete listing please visit the Seminar Schedule page, click here:
Seminar Schedule
Read about Dr. Hetland's contribution to BoneZone regarding GD&T and it's application focused on the medical component industry, click here.
BoneZone GDT Article 
 BONEZONE Archives
Contact Information:

Dr. Greg Hetland
Phone: (651) 275-8952
Fax: (612) 395-5405
IIGDT Logo Headquarters:

12159 Quail Ave. Lane N.
Stillwater, Minnesota 55082