CHAPTER 8 Material-Removal Processes: Cutting

Cutting Processes FIGURE 8.1 Examples of cutting processes.

Orthogonal Cutting FIGURE 8.2 Schematic illustration of a two-dimensional cutting process (also called orthogonal cutting).

Chip Formation FIGURE 8.3 (a) Schematic illustration of the basic mechanism of chip formation in cutting. (b) Velocity diagram in the cutting zone.

Chips Produced in Metal Cutting FIGURE 8.4 Basic types of chips produced in metal cutting and their micrographs: (a) continuous chip with narrow, straight primary shear zone; (b) secondary shear zone at the tool-chip interface; (c) continuous chip with built-up edge; (d) continuous chip with large primary shear zone; (e) segmented or nonhomogeneous chip; and (f) discontinuous chip. Source: After M. C. Shaw, P. K. Wright, and S. Kalpakjian.

Continuous Chip Formation FIGURE 8.5 Shiny (burnished) surface on the tool side of a continuous chip produced in turning.

Forces on a Cutting Tool FIGURE 8.11 Forces acting on a cutting tool in two-dimensional cutting.

Thrust Force/Rake Angle FIGURE 8.12 Thrust force as a function of rake angle and feed in orthogonal cutting of AISI 1112 cold-rolled steel. Note that at high rake angles, the thrust force is negative. A negative thrust force has important implications in the design of machine tools and in controlling the stability of the cutting processes. Source: After S. Kobayashi and E. G. Thomsen.

Orthogonal Cutting Data TABLE 8.1 Data on orthogonal cutting of 4130 steel. TABLE 8.2 Data on orthogonal cutting of 9445 steel.

Specific-Energy in Cutting TABLE 8.3 Approximate specific-energy requirements in cutting operations.

Temperature Distribution in the Cutting Zone FIGURE 8.16 Typical temperature distribution in the cutting zone. Note that the maximum temperature is about halfway up the face of the tool and that there is a steep temperature gradient across the thickness of the chip. Some chips may become red hot, causing safety hazards to the operator and thus necessitating the use of safety guards. Source: After G. Vieregge.

Terminology in Lathe Turning FIGURE 8.19 Terminology used in a turning operation on a lathe, where f is the feed (in./rev or mm/rev) and d is the depth of cut. Note that feed in turning is equivalent to the depth of cut in orthogonal cutting (Fig. 8.2), and the depth of cut in turning is equivalent to the turning is equivalent to the width of cut in orthogonal cutting. See also Fig. 8.42.

Machining Processes TABLE 8.7 General characteristics of machining processes.

Lathe Operations FIGURE 8.40 Various cutting operations that can be performed on a lathe.

Turning Operation FIGURE 8.42 (a) Schematic illustration of a turning operation showing depth of cut, d, and feed, f. cutting speed is the surface speed of the workpiece at the tool tip. (b) Forces acting on a cutting tool in turning. Fc is the cutting force; Ft is the thrust or feed force (in the direction of feed); and Fr is the radial force that tends to push the tool away from the workpiece being machined. Compare this figure with Fig. 8.11 for a two-dimensional cutting operation.

Cutting Speeds in Turning TABLE 8.8 Approximate range of recommended cutting speeds for turning operations.

Components of a Lathe FIGURE 8.44 Schematic illustration of the components of a lathe. Source: Courtesy of Heidenreich & Harbeck.

Computer-Numerical-Control Lathe FIGURE 8.45 A computer-numerical-control lathe. Note the two turrets on this machine. Source: Jones & Lamson.

Milling Operations FIGURE 8.53 (a) Schematic illustration of conventional milling and climb milling. (b) Slab-milling operation, showing depth of cut, d; feed per tooth, f; chip depth of cut, tc; and workpiece speed, v. (c) Schematic illustration of cutter travel distance to reach full depth of cut.

Face-Milling Operation FIGURE 8.54 Face-milling operation showing (a) action of an insert in face milling; (b) climb milling; (c) conventional milling; (d) dimensions in face milling. The width of cut, w, is not necessarily the same as the cutter radius. Source: Courtesy of The Ingersoll Cutting Tool Company.

Face-Milling Cutter FIGURE 8.55 Terminology for a face-milling cutter.

Cutters for Straddle and Form Milling FIGURE 8.58 Cutters for (a) straddle milling and (b) form milling.

Cutting Speeds in Milling TABLE 8.11 Approximate range of recommended cutting speeds for milling operations.

Horizontal-Spindle Milling Machine FIGURE 8.59 (a) Schematic illustration of a horizontal-spindle column-and-knee-type milling machine. (b) Schematic illustration of a vertical-spindle column-and-knee-type milling machine. Source: G. Boothroyd, Fundamentals of Machining and Machine Tools.