New ANSI/AGMA Accuracy Standards for Gears

Time for a Change For many years, the U.S. system of gear accuracy tolerances has been provided by AGMA 2000-A88, Gear Classification and Inspection Handbook. This document has been commonly used for gear accuracy specifications in contractual agreements for vendor-supplied gears. Also, it has often been used as the basis of internal company gear tolerance systems. The material within AGMA 2000-A88 has been carried forward without substantial change for nearly 40 years. It is widely considered to be outdated and in need of comprehensive revision, particularly with respect to the following issues: 1.) Lead tolerances in 2000-A88 are substantially larger than those found in other national gear accuracy standards. 2.) The standard lacks tolerances for cumulative pitch (a.k.a. index) deviations. 3.) The K-shaped tolerance band method provided in 2000-A88 for control of involute profile and helix (a.k.a. lead or tooth alignment) deviations is less desirable than line-fit tolerance methods found in other national gear accuracy standards. Recognizing that the standard was overdue for revision, the AGMA Inspection Handbook Committee developed a new suite of replacement documents. The first three of these new standards was published about a year ago. After the remaining documents are published in about a year, AGMA 2000-A88 will be withdrawn. Consequently, it is very important to understand the coming changes. The ISO Connection In recent years, AGMA technical standards development has increasingly focused upon achieving harmony with ISO gear standards. The AGMA Technical Division Executive Committee (TDEC) now requires technical committees to consider adoption of relevant ISO standards, wherever possible, instead of writing new AGMA documents. Also, it is required that all new standards produced by AGMA committees be in SI (metric) units of measure. These changes are seen by the AGMA as an important element in its increasing emphasis on assuring the competitiveness of the U.S. gear industry in the rapidly evolving world marketplace. With make/buy decisions becoming an increasingly prevalent issue for gear product users, selection of a genuinely international gear accuracy standard is increasingly attractive. Given the international makeup of ISO standards writing committees, their documents are viewed as inherently global in nature. The importance of ISO gear standards is expected to increase substantially in coming years. An example of the potential power of ISO standards can be seen in the widespread adoption of ISO 9000 standards. Accordingly, existing ISO gear accuracy standards and technical reports were used as starting templates, along with selected material from current AGMA standards, in the development of the new ANSI/AGMA standards. Also, AGMA hopes that much of the new material in its new accuracy standards will gain acceptance for inclusion in the next-generation ISO standards. Organization of Material AGMA 2000-A88 combined all of the materiNew ANSI/AGMA Accuracy Standards for Gears