Geometry of Single-point Turning Tools and Drills

To design a cutting tool and thus to assign its proper geometry, select the proper tool material and machining regime, one needs to know the physical essence of a metal cutting process starting with its definition and finishing with the easiest way to accomplish the objective of this process. This chapter provides guidelines to distinguish the metal cutting process commonly referred to as metal cutting among other closely related manufacturing processes and operations. It presents the known results and compares them with those used in other forming processes/operations. It argues that, if the usual notions are used, the metal cutting process does not have any distinguishing features. Analyzing what went wrong with the existing notions in metal cutting, this chapter provides a physically-based definition of the metal cutting process. Using the introduced definition, this chapter for the first time describes explicitly the role of cutting tool geometry in the metal cutting process that sets the stage for better understanding of other chapters in this book. Because in the development and implementation of any cutting tool experiment remains essential, the complete hierarchical system of tool testing is also discussed and the most useful similarity numbers used in testing are introduced and explained.

This chapter presents the basic terms and their definitions related to he cutting tool geometry according to ISO and AISI standards. It considers the tool geometry and inter-correlation of geometry parameters in three basic systems: tool-in-hand, tool-in-machine, and tool-in-use. It also reveals and resolves the common issues in the selection of geometry parameters including those related to indexable inserts and tool holders. The chapter introduces the concept and basics of advanced representation of cutting tool geometry using vector analysis. A step-by-step approach with self-sufficient coverage of terms, definitions, and rules makes this complicated subject simple as considerations begin with the simplest geometry of a single-point cutting tool and finish with summation of several motions. Extensive exemplification using practical cases enhances understanding of the covered material.

This chapter presents a general methodology for the selection of the optimal tool geometry based upon minimization of the work of plastic deformation in metal cutting. It argues that the chip compression ratio is the most objective yet simple ‘gage’ that should be used for the assessment of this work and thus to optimize the tool geometry. Individual and system influences of the major parameters of cutting tool geometry are discussed. The tool cutting edge, rake, flank and inclination angles, as well as edge preparation are included in considerations because these parameters have multi-faced influence on practically all aspects of the metal cutting process and greatly affect the outcome of a machining operation. The chapter offers explanations and rationales for many common perceptions and experimental knowledge concerning the listed parameters.

This chapter discusses classification, geometry, and design of straight flute and twist drills. It argues that the design, manufacturing, and implementation practices of drills are lagging behind the achievements in the tool materials, powerful high-speed-spindles rigid machines, and high-pressure MWF (coolant) supply. Although the wide availability CAD design tool and CNC precision grinding machines make it possible to reproduce any drill geometry, have not many new drill designs become available recently. The chapter points out that the prime objective of the drilling system is an increase in the drill penetration rate, i.e., in drilling productivity as the prime source for potential cost savings. As the major problem is in understanding particularities of drill geometry and its components, this chapter walks the reader from simple concepts starting from the basic terminology in drill design and geometry to the most complicated concepts in the field, keeping the context to the simplest possible fashion and providing practical examples. It provides an overview of important results concerning drill geometry and synthesizes the most relevant findings in the field with the practice of tool design.

This chapter discusses classification, geometry, and design of deep-hole drills. The concept of self-piloting is explained. The system approach to deep-hole machining is introduced and common system issues are discussed with examples. The major emphasis is placed on gundrills. A number of simple design rules are proposed and explained with examples. The conditions of free penetration of the drill into the hole being drilled are explained. The geometry consideration is systemically related to MWF flow and thus the concept of the optimum MWF flow rate is explained. A number of novel design concepts are revealed. This chapter also discusses system consideration in experimental study of gundrill parameters. It is demonstrated that tool life is a complex function not only of geometry parameters and machining regime alone but also of their combination. Tool geometry optimization using the Hooke and Jeeves method is also discussed.