description
Basic Gear Geometry
AGMA 933-B03 (reaffirmed October 3, 2017)

SCOPE
A clear and accurate understanding of the elements involved is indispensable to all who deal with the design, dimensioning, cutting and measurement of gear teeth.  The information here presented has been collected and arranged with the idea of making the important geometrical relationships as easy to see as possible with the intention of providing a sound basis for a thoroughly logical and comprehensive system of gear geometry.

The accurate exchange of ideas requires the exact definition and use of terms.  Nowhere is this true to a greater degree than in the case of the present subject.  Therefore, we will begin with a definition.

FOREWORD
[The foreword, footnotes and annexes, if any, in this document are provided for informational purposes only and are not to be construed as a part of AGMA Information Sheet 933-B03, Basic Gear Geometry.]

A paper entitled Gear Geometry, by Allan H. Candee, Mechanical Engineer, Gleason Works, was presented at the Annual Meeting of the American Gear Manufacturers Association in May, 1929.  The paper was an extension of the author’s ideas presented in ten blueprinted pages of diagrams, terms, and definitions to members of the AGMA Nomenclature Committee in April, 1928, under the title Universal Gear Geometry.

The paper of 1929 was reproduced in AMERICAN MACHINIST, July 4 and 11, 1929.  Later, in April, 1936, it was adopted by AGMA as a Recommended Practice, and reprints were distributed to members.  At that time, the letter symbols for angles were revised to conform to the standardization then under way in the Nomenclature Committee.

The 1959 publication of AGMA 115.01, Basic Gear Geometry, was essentially a reissue of the 1929 paper by Allan H. Candee.  The original wording was found to conform without need of change to the terms and definitions in AGMA 112.03, Gear Nomenclature.  Only minor editorial improvements were made, and a new term was introduced, profile angle, which is explained in the definitions.

This information serves as an introduction to and explanation of the geometrical relationships in gear teeth, but it does not in any way modify or affect standard gear nomenclature which is the outcome of conscientious efforts by the AGMA Nomenclature Committee which began more than seventy years ago.

The contents were reaffirmed by the AGMA Nomenclature Committee in 1988.  It was then submitted to the American National Standards Institute (ANSI) as a proposed national standard.  ANSI approved AGMA 115.01 as a national standard on September 7, 1989.

In 2000, the Technical Division Executive Committee voted to withdraw ANSI/AGMA 115.01 as a national standard and to return its contents back as an AGMA information sheet, duplicating Candee’s original work.  In a few instances, words have been deleted, ...., and added (italic), in an effort to make the meaning clear to today’s reader.

The first draft of AGMA 933-B03 was made in May, 2000.  It was approved by the AGMA Technical Division Executive Committee on October 20, 2002. 

Suggestions for improvement of this document will be welcome.  They should be sent to the American Gear Manufacturers Association, 500 Montgomery Street, Suite 350, Alexandria, Virginia  22314.

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