Your Source for GD&T Training
Based on The GD&T Hierarchy

Tec-Ease, Inc. provides the most comprehensive GD&T training and coaching in the industry. Our GD&T courses are designed to keep the participant interested and engaged, while having fun.

Your Source for GD&T Software
and Computer Based Training

Tec-Ease, Inc. software packages are designed to help train and offer continued support to companies and employees in the industrial manufacturing field.

We offer On-Site Courses,
Public Seminars,
Webinars and Computer Based Training.

Don’t Confuse Dimensioning with Tolerancing (#254)

(In accordance with the ASME Y14.5-2009 standard)

PDF available for premium site members.

Section 1 of the ASME Y14.5 standard is entitled "Scope, Definitions, and General Dimensioning".  It doesn’t say tolerancing.  Fifty years ago in Y14.5 there was minimal support for applying ± tolerances to locating dimensions.  About 30 years ago this minimal support in Y14.5 was removed in favor of basic dimensions and geometric tolerancing -- especially for controlling the location of features.  Yet, some people insist that Section 1 somehow legitimizes locating features using ± toleranced dimensions.  It doesn’t!

There is a figure in the Standard that is very similar to this first drawing. If these dimensions were all ± toleranced the drawing would have many different meanings depending on who is doing the reading.  There is no support in the ASME Y14.5 standard for using ± tolerancing on locating dimensions such as these.

However, if there is a note stating that UNTOLERANCED DIMENSIONS ARE BASIC and geometric tolerancing is applied as shown on the second drawing, there is only one meaning, no matter who does the reading.  So, let’s all move up to today’s print reading in accordance with the ASME Y14.5 standard.

Before you email me that the drawing is incomplete, read my Tip on Simultaneous Requirements.    

The video on the Premium Site will show you how each one of these symbols may be addressed using the ASME Y14.5-2009 standard.

Please email us any suggestions or topics that you would like to see covered in our Tip-of-the-Month series.

Max the Tec-Ease mascot

Learn About Premium Today!

Back to Tips Tip added Mar 2011