In contrast to most plastic deformation processes, the shape of a machined component is not uniquely defined by the tooling. Instead, it is affected by complex interactions between tool geometry, material properties, and frictional stresses and is further complicated by tool wear. This chapter covers the mechanics and tribology of metal cutting processes. It discusses the factors that influence chip formation, including tool and process geometry, cutting forces and speeds, temperature, and stress distribution. It reviews the causes and effects of tool wear and explains how to predict and extend the life of cutting tools based on the material of construction, the use of cutting fluids, and the means of lubrication. It presents various methods for evaluating workpiece materials, chip formation, wear, and surface finish in cutting processes such as turning, milling, and drilling. It also discusses the mechanics and tribology of surface grinding and other forms of abrasive machining.

There is a fairly wide variety of different tool steels for different applications. The American Iron and Steel Institute (AISI) classification of tool steels includes seven major categories: water-hardening tool steels, shock-resisting tool steels, cold work tool steels, hot work tool steels, low-alloy special-purpose tool steels, mold tool steels, high-speed tool steels, and powder metallurgy tool steels. This chapter provides discusses the manufacturing process, composition, properties, types, and applications of these tool steels and other cutting tool materials, such as cemented carbides. It also describes the methods of applying coatings to cutting tools to improve tool life.

High-speed tool steels have in common the ability to maintain high hardness at elevated temperatures. High speed steels are primarily used for cutting tools that generate heat during high-speed machining. They are designated as group M or group T steels in the AISI classification system, depending on whether the major alloying approach is based on molybdenum or tungsten. This chapter describes the effects of each of the alloying elements and carbon content on the processing, microstructures, and properties of high-speed steels. It discusses the processes involved in the solidification, hot work, annealing, austenitizing for hardening, and tempering of high-speed steels. It also discusses the processes involved in controlling grain size during austenitizing and reviews the characteristics of cooling transformations and other property changes in tempered high-speed steels. Information on multipoint cutting tools is provided. The chapter discusses the applications of high-speed tool steel and factors in selecting high-speed tool steels.

The qualities that make superalloys excellent engineering materials also make them difficult to machine. This chapter discusses the challenges involved in machining superalloys and the factors that determine machinability. It addresses material removal rates, cutting tool materials, tool life, and practical issues such as set up time, tool changes, and production scheduling. It describes several machining processes, including turning, boring, planing, trepanning, shaping, broaching, drilling, tapping, thread milling, and grinding. It also provides information on toolholders, fixturing, cutting and grinding fluids, and tooling modifications.

This chapter discusses the factors that influence the cost and complexity of machining titanium alloys. It explains how titanium compares to other metals in terms of cutting force and power requirements and how these forces, along with cutting speeds and the use of cutting fluids, affect tool life, surface finish, and part tolerances. The chapter also includes a brief review of nontraditional machining methods.

This chapter covers the practical aspects of machining, particularly for turning, milling, drilling, and grinding operations. It begins with a discussion on machinability and its impact on quality and cost. It then describes the dimensional and surface finish tolerances that can be achieved through conventional machining methods, the mechanics of chip formation, the factors that affect tool wear, the selection and use of cutting fluids, and the determination of machining parameters based on force and power requirements. It also includes information on nontraditional machining processes such as electrical discharge, abrasive jet, and hydrodynamic machining, laser and electron beam machining, ultrasonic impact grinding, and electrical discharge wire cutting.