<div class="htmlview paragraph">Stating that the production of satisfactory gears is one of the most serious problems confronting the automobile builder, the authors give an outline of the practice of producing gears that is used by the company they represent and describe a new method for cutting the rear-axle drive-pinion by using two machines, each machine cutting one side of the teeth. Explanations are given of the various steps in the process and the reasons for stating that this method is not only cheaper but produces gears of higher quality. Numerous suggestions are made for improving gears and axles, and the claim is made that it is doubtful if the spiral-bevel gear has had a fair chance because axles usually have not been designed so that the main consideration was the requirements of the gears.</div> <div class="htmlview paragraph">The results of a number of experiments with transmission-gears seem to indicate that, to get the greatest degree of quietness, every effort should be made to increase the number of teeth in contact and to improve the profile and the tooth spacing. Various kinds of gear-steel are discussed, together with heat-treatments which have given good results. Research work, undertaken to explain variations in machining, in physical properties and in service that cannot be accounted for by chemical analysis or the microscope, has shown a variation in the steel itself which has been found by fracturing samples from the bars after heat-treatment and by a study of the grain size of the steel.</div>