INTRODUCTION

It is a real pleasure and privilege to appear before this fine group. In looking over the imposing list of speakers who have appeared here and the subjects on which they have addressed you, it is apparent at once that your programs have been of a very high order. And one who now appears with a subject as old as bevel gears must ask himself what he has to say that may be of interest and possibly of some value. We cannot answer that question without referring, perhaps rather frequently, to the Gleason Works of Rochester, New York. We make no apology for these references. After all, it is because the Gleason Works has been working on bevel gear machinery and bevel gears for seventy-five years that we have been invited to present this topic here today. We shall endeavor to show some of the progress that has been made in that time, and what is the state of the art today, and we shall be very happy if, in doing so, we can transmit to you some of the interest we have in this subject.

Bevel gears have long been known and used where it was necessary to make a power drive turn a corner. But the methods of making them were rough, and at best only approximate. In 1874 William Gleason, who had organized the Gleason Works in 1865, invented the first practical machine for correctly cutting the teeth of bevel gears. This machine used a single planing type tool, and copied a form to produce the profile shape of the tooth, cutting one side of a tooth at a time. It was far from being fully automatic, and was not very fast in operation according to present day standards, but it incorporated the important principle of a bevel gear cutting machine in that it automatically produced a correctly tapering tooth shape. This was a great advance over using cast tooth gears, or teeth shaped by hand, or gear teeth cut with a formed milling cutter. These latter could be correct at only one point on the face length of the tooth, and had to be laboriously hand filed to bring them to an approximate shape at all other points.

For some years following, this type of machine was developed and improved. At the same time, the field for the use of correctly cut bevel gears was constantly increasing. In the 1890's the use of bevel gears in the chainless bicycle gave a temporary spurt to operations in this field. With the advent of the automobile, however, the demand for correctly cut bevel gears of a high degree of accuracy for rear axle drives increased tremendously. The Gleason Works had given up the manufacture of a general line of machine tools by this time to concentrate on bevel gear machinery, and from the beginning of the century up to the present day there have followed a number of important inventions and developments that have brought the production of bevel and hypoid gears to a very highly developed art, featuring extreme accuracy, high quality finish and rapid production. Most important among these developments are the following:

1905 Development of the two-tool bevel gear generator for cutting straight tooth bevel gears. This machine found an immediate market in the infant automobile industry for cutting the rear axle drive gears and the equalizing gears of the differential.
1913 Invention of the process and tool and machine for cutting the teeth of spiral bevel gears. The inherent advantages of spiral bevel gears caused them to supplant straight bevel gears in the final drive of almost all motor cars, and in many other drives where high speed and quietness were required.
1925 Invention of a practical method for the manufacture of hypoid gears. This type of gear with the axis of one member of the pair offset from the axis of the other makes possible the use of designs in which the driving and driven shafts pass one another. In automobiles the use of hypoid gears improves car design by lowering the propeller shaft -- and consequently the floor -- and provides better performance.
1931-38 Development of machines and methods for grinding the teeth of spiral bevel and hypoid gears and pinions. This process has been made fast, and entirely practical. It has the advantage of removing all distortion due to heat treat, and of producing the last word in accuracy.
1937 Invention and development of the Revacycle machine, cutter and process, for the fast production of differential gears in mass quantities. This is the fastest known method of cutting straight tooth bevel gears, and consists of completely cutting a tooth from the solid in a single revolution of a disc type cutter.

Along with these outstanding developments has gone the design and manufacture of many other machines for the principal and auxiliary operations of bevel gear production -- rough cutting machines for both straight and spiral bevel and hypoid gears and pinions; testing machines for proving the quality of cut gears; lapping machines for a final smoothing operation; quenching presses and surface hardening machines for control of heat treatment; sharpening machines for all cutters and tools used in the cutting operations; and numerous other machines, devices and processes required in gear production. So that at the present time there is offered a complete and fully integrated line of equipment. A notable feature of all this equipment is that it is thoroughly practical to use. Policy has always been not to offer any equipment that could not be completely and easily handled in operation by the user. Coupled with this is a complete engineering service readily available for the study of gear problems, and to furnish the best information as to the design and installation of bevel and hypoid gears, with the result that the gear manufacturing equipment can be used to the best possible advantage.