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Teaching Applied Measuring Methods Using GD&T

Abstract

Products are generally specified using the American Society of Mechanical Engineers’ 1994 standard Y 14.5M on Geometric Dimensioning and Tolerancing, commonly known as GD&T. Engineering technology graduates who work in design, or manufacturing, or quality, need to have expertise in the principles of measurement science and practical interpretation of GD&T- based product specifications.

A new course on metrology has been recently introduced in an engineering technology curriculum where students apply the GD&T theory in to practice by inspecting parts using these GD&T tolerance specifications.

The paper describes the highlights of metrology course and some of the experiments that students do to measure using GD&T methods. The paper also discusses the lessons learned from the students’ performance in class and laboratory, and gives their feedback on the extent of achieving the proposed course outcomes.

Introduction

All manufactured products require an accurate and precise scale of measurement to check their conformance to specifications. Much of today’s industry and technology relies on accurate measurement. Manufactured products are measured by instruments to check their conformance to specifications based on GD&T standards. This need is all the more important in the present global economy as measurement error causes false fails and false passes both of which are expensive.

Understanding the practical principles of measurement science using GD&T should be an important part of engineering technology education which helps to impart the hands-on aspect of the subject area.

There is a basic metrology course at the freshman/sophomore level that teaches principles of hands-on measurements using common instruments such as vernier calipers, different types of vernier micrometers, gage blocks, dial indicators, and CMMs (Coordinate Measuring Machines). It was decided to develop the new higher-level metrology course at the junior/senior level that would supplement the material covered in the basic course. Also, students learn the GD&T theory in their freshman/sophomore level from the point of view of draftsperson and designer, and in this new metrology course they apply the theory in understanding and making correct GD&T measurements.

In this course, students learn the types and causes of measurement errors, perform measurement setups using most of the geometric tolerances such as, size tolerance, flatness, straightness, circularity, parallelism, angularity, circular and total runouts, concentricity, and position tolerancing. They also learn the concepts of functional gage design for both soft and hard gages.

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Narang, R. (2008, June), Teaching Applied Measuring Methods Using Gd&T Paper presented at 2008 Annual Conference & Exposition, Pittsburgh, Pennsylvania. 10.18260/1-2--3561