CHAPTER 8 Material-Removal Processes: Cutting

1
CHAPTER 8Material-Removal Processes Cutting
2
Cutting Processes

• FIGURE 8.1 Examples of cutting processes.

3
Orthogonal Cutting

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

4
Chip Formation

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

5
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.

6
Continuous Chip Formation

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

7
Chips Produced In Turning

• FIGURE 8.8 Various chips produced in turning
  (a) tightly curled chip (b) chip hits workpiece
  and breaks (c) continuous chip moving away from
  workpiece and (d) chip hits tool shank and
  breaks off. Source G. Boothroyd, Fundamentals of
  Metal Machining and Machine Tools.

8
Oblique Cutting

• FIGURE 8.9 (a) Schematic illustration of
  cutting with an oblique tool. (b) Top view,
  showing the inclination angle i. (c) Types of
  chips produced with different inclination angles.

9
Right-Hand Cutting Tool

• FIGURE 8.10 (a) Schematic illustration of a
  right-hand cutting tool. Although these tools
  have traditionally been produced from solid
  tool-steel bars, they have been largely replaced
  by carbide or other inserts of various shapes and
  sizes, as shown in (b).

10
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.

11
Types of Cutting Tool Wear

• FIGURE 8.20 (a) Types of wear observed in
  cutting tools. The thermal cracks shown are
  usually observed in interrupted cutting
  operations, such as in milling. (b) Catastrophic
  failure of tools. (c) Features of tool wear in a
  turning operation. The VB indicates average flank
  wear. Source (a) and (b) After V. C. Venkatesh.
  (c) International Organization for
  Standardization (ISO).

12
Crater and Flank Wear on a Tool

• FIGURE 8.21 (a) Crater wear and (b) flank wear
  on a carbide tool. Source J. C, Keefe, Lehigh
  University.

13
Range of Surface Rough-nesses

• FIGURE 8.27 Range of surface roughnesses
  obtained in various machining processes. Note the
  wide range within each group. (See also Fig.
  9.27).

14
Carbide Inserts

• FIGURE 8.32 (a) Typical carbide inserts with
  various shapes and chip-breaker features. Round
  inserts are also available. The holes in the
  inserts are standardized for interchangeability.
  Source Courtesy of Kyocera Engineered Ceramics,
  Inc., and Manufacturing Engineering, Society of
  Manufacturing Engineers. (b) Methods of attaching
  inserts to a tool shank by clamping, (c) with
  wing lockpins, and (d) with a brazed insert on a
  shank.

15
Relative Edge Strength

• FIGURE 8.33 Relative edge strength and tendency
  for chipping and breaking of inserts with various
  shapes. Strength refers to that of the cutting
  edge shown by the included angles. Source
  Kennametal, Inc.

FIGURE 8.34 Edge preparation of inserts to
improve edge strength. Source Kennametal, Inc.
16
Properties of Tool Materials

• FIGURE 8.38 Ranges of properties for various
  groups of tool materials. (See also various
  tables in this chapter.)

17
Construction of Insert

• FIGURE 8.39 Construction of polycrystalline
  cubic-boron-nitride or diamond layer on a
  tungsten-carbide insert.

18
Machining Processes

• TABLE 8.7 General characteristics of machining
  processes.

19
Lathe Operations

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

20
Designations for a Right-Handed Cutting Tool

• FIGURE 8.41 (a) Designations and symbols for a
  right-hand cutting tool solid high-speed-steel
  tools have a similar designation. The designation
  right hand means that the tool travels from
  right to left, as shown in Fig. 8.19 (b) Square
  insert in a right-hand toolholder for a turning
  operation. A wide variety of toolholder is
  available for holding inserts at various angles.
  Thus, the angles shown in (a) can be achieved
  easily by selecting an appropriate insert and
  toolholder. Source Kennametal, Inc.

21
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.

22
Range of Cutting Speeds

• FIGURE 8.43 The range of applicable cutting
  speeds and fees for a variety of tool materials.
  Source Valenite, Inc.

23
Cutting Speeds in Turning

• TABLE 8.8 Approximate range of recommended
  cutting speeds for turning operations.

24
Components of a Lathe

• FIGURE 8.44 Schematic illustration of the
  components of a lathe. Source Courtesy of
  Heidenreich Harbeck.

25
Machine Tool Parts Example

• FIGURE 8.46 Typical parts made on
  computer-numerical-control machine tools.

26
Chisel and Crankshaft-Point Drills

• FIGURE 8.48 (a) Standard chisel-point drill,
  with various features indicated. (b)
  Crankshaft-point drill.

27
Drills and Drilling Operations

• FIGURE 8.49 Various types of drills and
  drilling operations.

28
Speeds and Feeds in Drilling

• TABLE 8.10 General recommendations for speeds
  and feeds in drilling.

29
Reamer and Tap Terminology

• FIGURE 8.50 Terminology for a helical reamer.

FIGURE 8.51 Terminology for a tap.
30
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.