FOREWORD This system for the design of spiral bevel gears is a revision of the original Gleason System adopted by the AGMA and revised in 1942. Changes and additions are as following: a) Adoption of 20 degrees as the basic pressure angle@ instead of the former 141/2 degrees; b) Angular gear design data; c) Revision of tooth thickness calculations to give approximately equal stress in gear and pinion; d) Replacement of the table for gear addendums by the formula for the same. The text describes the general basis of the system and shows the calculations used to obtain the tooth proportions and blank dimensions.