Metal removal processes for gear manufacture can be grouped into two general categories: rough machining (or gear cutting) and finishing (or high-precision machining). This chapter discusses the processes involved in machining for bevel and other gears. The chapter describes the type of gear as the major variable and discusses the machining methods best suited to specific conditions. Next, the chapter provides information on gear cutter material and nominal speeds and feeds for gear hobbing. Further, it describes the cutting fluids recommended for gear cutting and presents a comparison of steels for gear cutting. The operating principles of computer numerical control and hobbing machines are also covered. This is followed by sections that discuss the processes involved in grinding, honing, and lapping of gears. Finally, the chapter provides information on the superfinishing of gears.

This chapter begins with a review of some of the terms used in the gear industry to describe the design of gears and gear geometries. It then discusses the types of gears that operate on parallel shafts, intersecting shafts, and nonparallel and nonintersecting shafts. Next, the processes involved in the selection of gear are discussed, followed by information on the basic stresses applied to a gear tooth, the strength of a gear tooth, and the most widely used gear materials. Further, the chapter briefly reviews gear manufacturing methods and the heat treating processing steps including prehardening processes, through hardening, and case hardening processes.

Gear manufacture depends on machinery available, design specifications or requirements, cost of production, and type of material from which the gear is to be made. This chapter discusses the processes involved in methods for manufacturing gears, namely casting, forming, and forging.

Several limitations in achieving optimal gear performance with conventional nitriding have led researchers to work on a variety of novel and improved nitriding processes. Of these, ion/plasma nitriding offers some promising results, which are reviewed in this chapter. The chapter concludes with a case history describing the application of ion nitriding to an internal ring gear of an epicyclic gearbox.

Drawing is a bulk deformation process that involves significant surface generation and high pressures. This chapter provides an overview of the mechanics and tribology of wire, bar, tube, and shape drawing. It presents important equations for calculating stresses, forces, friction, heat, strain, and distortion for different tooling configurations and geometries. It explains how to select and apply lubricants based on drawing speed, die design, and other factors and how to maintain sufficient film thickness for hydrodynamic, mixed, and solid-film lubrication conditions. It also discusses the use of vibrating dies, the influence of surface finish and defects, and lubrication practices for specific materials.

Powder metallurgy (P/M) is a flexible metalworking process for the production of gears. The P/M process is capable of producing close tolerance gears with strengths to 1240 MPa at economical prices in higher volume quantities. This chapter discusses the capabilities, limitations, process advantages, forms, tolerances, design, tooling, performance, quality control, and inspection of P/M gear manufacture. In addition, it presents examples that illustrate the versatility of the P/M process for gear manufacture.

This chapter opens with a discussion of the classification of rod and tube extrusion processes. The standard processes involve hot working (extrusion at temperatures above room temperature), but some specialized cold working processes are also used for rod and tube extrusion. The next section reviews principles, variations, thermal conditions, axial load calculation, material flow, and applications of direct extrusion and indirect extrusion, with examples provided for extrusion of aluminum and copper alloys. Next, the chapter focuses on the process principles, advantages, and applications of conventional hydrostatic extrusion and thick film processes. This is followed by sections providing information on the special extrusion processes, namely conform process and cable sheathing. The chapter ends with a discussion on direct and indirect tube extrusion.

The primary objective of carburizing and hardening gears is to secure a hard case and a relatively soft but tough core. For this process, low-carbon steels (up to a maximum of approximately 0.30% carbon), either with or without alloying elements (nickel, chromium, manganese, molybdenum), normally are used. The processes involved in hardening, tempering, recarburizing, and cold treatment of carburized and quenched gears are discussed. Next, the chapter reviews the selection of materials for carburized gears and considerations related to carbon content, core hardness, and microstructure. This is followed by sections discussing some problems that can be experienced in the carburizing process and how these can be addressed, including a section on shot peening to induce compressive residual stress at and below the surface. It then discusses the applications of carburized gears and finally presents a case history of distortion control of carburized and hardened gears.

The wear caused by contact stress fatigue is the result of a wide variety of mechanical forces and environments. This chapter discusses the characteristics of four types of contact stress fatigue on mating metal surfaces: surface, subsurface, subcase, and cavitation. Features and corrective actions for these contact stress fatigue are discussed. The chapter also lists some possible ways to reduce the cavitation fatigue problem.

Gears can fail in many different ways, and except for an increase in noise level and vibration, there is often no indication of difficulty until total failure occurs. This chapter begins with the classification of gear failure modes, followed by sections discussing the characteristics of various fatigue failures. Then, it provides information on the modes of impact fractures, wear, scuffing, and stress rupture. Next, the chapter describes the causes of gear failures and discusses the processes involved in conducting the failure analysis. Finally, the chapter presents examples of gear failure analysis.

The chapter covers various aspects of biotribology in the context of dental care, orthopedic implants, haptics, eyewear, and stents and fixation devices. It also addresses the issue of biocompatibility and the effects of friction and contact pressure on skin.

This appendix is a glossary of terms and definitions associated with sheet metal forming.

This chapter describes how aluminum sheet and foil alloys are processed to produce functional, economical packages that meet the various industry performance criteria. The focus is on the key customer requirements for three main application segments: foil, cans, and impact extrusions. A huge range of products in this industry segment is also illustrated. The need for sustainable production and recyclability is also discussed.

This chapter provides details on several specific binder formulations and a discussion of basic binder design concepts. The focus is on customization of the feedstock response to heating, pressurization, or solvent exposure for a specific shaping process. The discussion starts with the requirements of a binder system, the historical progression of binder formulations, and the use of binder alternatives to adapt to specific applications. The importance of binder handling strength to shape preservation is emphasized. The chapter provides information on the binders used for room-temperature shaping, namely slurry and tape casting systems.

This chapter describes the properties and attributes of various classes of metalworking lubricants, including mineral oils; natural oils, fats, derivatives, and soaps; synthetic fluids (olefins, esters, polyglycols, ionic liquids); compounded lubricants (oils, greases, fats); aqueous lubricants (emulsions, synthetics, solutions); and a wide range of coatings and carriers. It also discusses solid-film lubricants (oxide films, polymer films, layer-lattice compounds) and environmental and safety concerns.

This chapter discusses the causes and effects of wear along with prevention methods. It covers abrasive, erosive, erosion-corrosion, grinding, gouging, adhesive, and fretting wear. It also discusses various forms of contact-stress fatigue, including subsurface-origin fatigue, surface-origin fatigue, subcase-origin fatigue (spalling fatigue), and cavitation fatigue.