Cylindrical Gears — ISO System of Flank Tolerance Classification — Part 2: Definitions and Allowable Values of Double Flank Radial Composite Deviations

ANSI/AGMA ISO 1328-2-A21

ANSI/AGMA ISO 1328-2-A21


This document establishes a gear tooth classification system relevant to double flank radial composite deviations of individual cylindrical involute gears and sector gears. It specifies the appropriate definitions of gear tooth deviations, the structure of the gear tooth flank classification system, and the allowable values of the gear tooth deviations. It provides formulae to calculate tolerances for individual product gears when mated in double flank contact with a master gear. Tolerance tables are not included.

This document is applicable to gears with three or more teeth that have reference diameters of up to 600 mm.

This document does not provide guidance on gear design nor does it recommend tolerances.


In 2016, the AGMA Gear Accuracy Committee, acting as the US TAG to ISO TC 60/WG 2, proposed ANSI/AGMA 2015-2-B15 as the basis for the revision of ISO 1328-2.

ISO 1328-2:2020 was published by ISO TC 60. The new revised standard replaces the first edition, ISO 1328-2:1997. 

The main changes compared to the previous edition are as follows:

  • the document title of this part has been revised to correspond to that of part 1 and better reflect the contents of this part;
  • the scope of applicability has been expanded to include sector gears;
  • revisions have been made to the formulae which define the double flank radial composite tolerances, and the range of classification numbers has been changed to clarify the independence of this classification system from that given in part 1;
  • the change in tolerance value between consecutive tolerance classes has been reduced, so two steps in the new system results in the same change as one step of the old system, but approximately the same global range of tolerance values is maintained with additional steps;
  • annexes have been added to describe complementary information and examples;
  • evaluation of runout, previously handled in this document, has been moved to ISO 1328-1:2013;
  • advice on appropriate inspection methods has been removed; the information can be found in ISO/TR 10064-2.

The AGMA Gear Accuracy Committee voted to adopt the new ISO 1328-2:2020 in October 2020. The first draft of ANSI/AGMA ISO 1328-2-A21 was made in January 2021. It was approved by the AGMA membership in May 2021. It was approved as an American National Standard on October 22, 2021.


The following documents are referred to in the text in such a way that some or all their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 701, International gear notation — Symbols for geometrical data

ISO 1122-1, Vocabulary of gear terms — Part 1: Definitions related to geometry

ISBN: 978-1-64353-115-1

Pages: 26

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