The quality of the finished gear is influenced by the very first machining operations of the blank. Since the gear tooth geometry is generated on a continuously rotating blank in hobbing or shaping, it is important that the timed relationship between the cutter and workpiece is correct. If this relationship is disturbed by eccentricities of the blank to its operating centerline, the generated gear teeth will not be of the correct geometry. During the blanking operations, the gear's centerline and locating surfaces are established and must be maintained as the same through the following operations that generate the gear teeth.

The modern day requirement for precision finished hobbed gears, coupled with the high accuracy characteristics of modern CNC hobbing machines, demands high tool accuracy.

The last decade has been a period of far-reaching change for the metal working industry. The effect of higher lubricant costs, technical advances in machine design and increasing competition are making it essential that manufacturers of gears pay more attention to testing, selecting and controlling cutting fluid systems. Lubricant costs are not a large percentage of the process cost relative to items such as raw materials, equipment and labor, and this small relative cost has tended to reduce the economic incentive to evaluate and to change cutting fluids.

Rotary gear honing is a hard gear finishing process that was developed to improve the sound characteristics of hardened gears by: Removing nicks and burrs; improving surface finish; and making minor corrections in tooth irregularities caused by heat-treat distortion.

In the gearing industry, gears are lubricated and cooled by various methods. At low to moderate speeds and loads, gears may be partly submerged in the lubricant which provides lubrication and cooling by splash lubrication. With splash lubrication, power loss increases considerably with speed. This is partially because of churning losses. It is shown that gear scoring and surface pitting can occur when the gear teeth are not adequately lubricated and cooled.

The search for greater gear life involves improvement in cost, weight and increased power output. There are many events that affect gear life, and this paper addresses those relating to fatigue, gear tooth pitting, fatigue strength losses due to the heat treating processes and shot peening technique. The capability of shot peening to increase fatigue strength and surface fatigue life eliminate machine marks which cause stress risers, and to aid in lubrication when properly controlled, suggests increased use and acceptance of the process.

October 5-8, 1986 AGMA Fall technical Conference & Gearing Exhibit September 17-19, 1986 Ohio State University Gear Noise Seminar November 11-13, 1986 SME Gear Processing and Manufacturing Clinic November 19-21, 1986 Seminar: Gear System Design for Minimum Noise

Anyone involved in the design, manufacture and use of gears is concerned with three general characteristics relative to their application: noise, accuracy, and strength or surface durability. In the article, we will be dealing with probably the most aggravating of the group, gear noise.

The manufacturing process to produce a gear essentially consist of: material selection, blank preshaping, tooth shaping, heat treatment, and final shaping. Only by carefully integrating of the various operations into a complete manufacturing system can an optimum gear be obtained. The final application of the gear will determine what strength characteristics will be required which subsequently determine the material and heat treatments.

Gear surface fatigue endurance tests were conducted on two groups of 10 gears each of carburized and hardened AlSI 9310 spur gears manufactured from the same heat of material