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Walsh, Ronald A.
McGraw-Hill machining and metalworking handbook / Ronald A. Walsh.
and Denis R. Cormier—3rd ed.
p. cm.
ISBN 0-07-145787-9
1. Machining—Handbooks, manuals, etc. 2. Metal-work—Handbooks,
manuals, etc. I. Cormier, Denis R. II. Title.
TJ1185.W35 2005
2005051055
Copyright © 2006, 1999, 1994 by The McGraw-Hill Companies, Inc.
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Walsh CH01 8/30/05 8:39 PM Page 1
Source: McGraw-Hill Machining and Metalworking Handbook
Chapter
1
Modern Metalworking
Machinery, Tools,
and Measuring Devices
Metalworking machinery, tools, and measuring instruments have
advanced considerably over the past 50 years. This chapter will show
some of the new machines, tools, and instruments used throughout
industry today that allow us to produce parts faster and more accu-
rately than was possible in the past. The widespread use and imple-
mentation of microprocessors to control the actions of metalworking
machinery is evident in many of the photographs of modern equipment
shown in this chapter. Photographs of other modern metalworking
machinery appear throughout this Handbook.
1.1 Metalworking Process Overview
When a metal part is fabricated, the part blank either can come from
a near-net-shape manufacturing process or it can come in the form of
bars, rods, plates, etc. Metal casting processes such as die casting,
sand casting, and investment casting are the most common methods
of producing a part blank that is close to its final shape (i.e., near net
shape). Recent years also have seen a flood of new solid freeform fab-
rication (SFF) processes that are capable of directly producing near-
net-shape functional metal parts without the need for molds, dies,
etc. (see Chap. 10). In the case of near-net-shape processes, rough
1
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2 Chapter One
machining of large amounts of stock is not necessary. Instead, it is
only necessary to finish machine those features that are critical to
the function of a part.
1.1.1 Primary processes
Die casting. Small or medium-sized parts in nonferrous alloys such
as magnesium, aluminum, and zinc are injected under pressure
into a steel die. A machining allowance of 0.25 to 0.5 mm (0.010 to
0.020 in) for critical features is typical.
Sand casting. Molten metal is cast into a packed-sand mold. Parts
weighing from just a few ounces to several tons can be sand cast. The
most commonly sand-cast metals include irons, stainless steels,
aluminum, and nickel alloys. Since the surface of the cast part is
textured, a machining allowance typically is provided for critical fea-
tures. Recommended machining allowances for a variety of metals
are provided in Table 1.1.
Investment casting. Both ferrous and nonferrous metals may be
investment cast into a single-use refractory ceramic mold. High-
temperature-reactive metals such as titanium typically are vacuum
investment cast.
Forging. Metals such as nonferrous alloys (e.g., aluminum, magne-
sium, and brass), steels, and nickel alloys are relatively easy to forge.
The slugs are essentially hammered by a die such that the metal
deforms to the shape of the die. Recommended machining allowances
for a variety of metals are provided in Table 1.2.
Powder metallurgy. Metal powder is compacted by a die and then
sintered to hold its shape. The resulting parts are porous and option-
ally are infiltrated to 100 percent density.
Extrusion. A heated billet is forced through a die opening such that
the length of the billet takes on the cross-sectional shape of the die
opening.
1.1.2 Metal-cutting processes
CNC machining. The two most versatile machines in the modern
machining industry are the computer numerical control (CNC)
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Modern Metalworking Machinery, Tools, and Measuring Devices 3
TABLE1.1 Sand Casting Allowances for Each Side
Allowance, mm (in)
Casting size, mm (in)* Drag and sides Cope surface
Gray iron Up to 150 (up to 6) 2.3 (3⁄32) 3 (1⁄8)
150–300 (6–12) 3 (1⁄8) 4 (5⁄32)
300–600 (12–24) 5 (3⁄16) 6 (1⁄4)
600–900 (24–36) 6 (1⁄4) 8 (5⁄16)
900–1500 (36–60) 8 (5⁄16) 10 (3⁄8)
1500–2100 (60–84) 10 (3⁄8) 13 (1⁄2)
2100–3000 (84–120) 11 (7⁄16) 16 (5⁄8)
Cast steel Up to 150 (up to 6) 3 (1⁄8) 6 (1⁄4)
150–300 (6–12) 5 (3⁄16) 6 (1⁄4)
300–600 (12–24) 6 (1⁄4) 8 (5⁄16)
600–900 (24–36) 8 (5⁄16) 10 (3⁄8)
900–1500 (36–60) 10 (3⁄8) 13 (1⁄2)
1500–2100 (60–84) 11 (7⁄16) 14 (9⁄16)
2100–3000 (84–120) 13 (1⁄2) 19 (3⁄4)
Malleable Up to 75 (up to 3) 1.5 (1⁄16) 2.3 (3⁄32)
iron 75–300 (3–12) 2.3 (3⁄32) 3 (1⁄8)
300–450 (12–18) 3 (1⁄8) 4 (5⁄32)
450–600 (18–24) 4 (5⁄32) 5 (3⁄16)
Ductile Up to 150 (up to 6) 2.3 (3⁄32) 6 (1⁄4)
iron 150–300 (6–12) 3 (1⁄8) 10 (3⁄8)
300–600 (12–24) 5 (3⁄16) 19 (3⁄4)
600–900 (24–36) 6 (1⁄4) 19 (3⁄4)
900–1500 (36–60) 8 (5⁄16) 25 (1)
1500–2100 (60–84) 10 (3⁄8) 28 (11⁄8)
2100–3000 (84–120) 11 (7⁄16) 32 (11⁄4)
Nonferrous Up to 150 (up to 6) 1.6 (1⁄16) 2.3 (3⁄32)
metals 150–300 (6–12) 2.3 (3⁄32) 3 (1⁄8)
300–600 (12–24) 3 (1⁄8) 4 (5⁄32)
600–900 (24–36) 4 (5⁄32) 5 (3⁄16)
*Casting sizerefers to the overall length of the casting and not to the length
of a particular measurement.
SOURCE:Bralla, J., Design for Manufacturability Handbook.New York: McGraw-
Hill, 1999.
millingmachine (Fig. 1.1) and the CNC lathe (Fig. 1.2). A key to the
versatility of these machines is the automatic tool changer. Vertical
machining centers (VMCs) such as the one shown in Fig. 1.1 include
a carousel that holds many different cutting tools such as milling
cutters, drills, reamers, and taps. The automatic tool changer
changes cutting tools between machining operations without any
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4 Chapter One
TABLE1.2 Typical Machining Allowances for Forgings
Forging size: Projected area at parting line, mm (in)
Alloy To 640 cm2 To 2600 cm2 Over 2600 cm2
family (100 in2) (400 in2) (400 in2)
Aluminum 0.5–1.5 1.0–2.0 1.5–3.0
(0.020–0.060) (0.040–0.080) (0.060–0.120)
Magnesium 0.5–1.5 1.0–2.0 1.5–3.0
(0.020–0.060) (0.040–0.080) (0.060–0.120)
Brass 0.5–1.5 1.0–2.0 1.5–3.0
(0.020–0.060) (0.040–0.080) (0.060–0.120)
Steel 0.5–1.5 1.5–3.0 3.0–6.0
(0.020–0.060) (0.060–0.120) (0.120–0.240)
Stainless 0.5–1.5 1.5–2.5 1.5–5.0
steel (0.020–0.060) (0.060–0.100) (0.060–0.200)
Titanium 0.8–1.5 — 2.0–6.0
(0.030–0.060) (0.080–0.240)
Niobium 0.8–2.5 — —
(0.030–0.100)
Tantalum 0.8–2.5 — —
(0.030–0.100)
Molybdenum 0.8–2.0 2.0–3.0 —
(0.030–0.080) (0.080–0.120)
SOURCE:Bralla, J., Design for Manufacturability Handbook.New York: McGraw-
Hill, 1999.
user intervention, thus allowing several machining operations to
be executed in a single workpiece setup. Likewise, the CNC lathe
in Fig. 1.2 incorporates an automatic tool changer that can switch
between tools that perform facing, knurling, grooving, boring, and
many other turning operations.
Electric discharge machining (EDM). EDM comes in two forms—sinker
EDM and wire EDM. Sinker EDM uses spark erosion to machine a
workpiece with a graphite or copper electrode whose shape is the
negative of the cavity being machined. Wire EDM uses spark ero-
sion with a wire to cut two-dimensional (2D) profiles.
Laser machining. A powerful laser beam coupled with a CNC motion-
control system is used to cut 2D profiles in sheet or plate material.
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Modern Metalworking Machinery, Tools, and Measuring Devices 5
Figure 1.1 Vertical machining center.
Figure 1.2 CNC lathe.
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6 Chapter One
Complex, thin parts whose quantity does not warrant a hard die
are produced using this method.
Chemical milling. Large masses of metal may be removed effectively
in producing a part using the etching action of chemicals. Very thin
and delicate parts also may be produced with chemical milling or
etching. A tough photoresistive substance covers the parts of the
metal that are not to be removed. Printed circuit board production
is actually a chemical milling operation.
Waterjet machining. A very high pressure jet of water, loaded with
microfine abrasives, is used to cut the sheet or plate material of
metal, plastic, glass, or other composition. As is the case with laser
machining, waterjet machining is useful when the production vol-
umes do not warrant a hard die. The absence of a heat-affected
zone is advantageous as well. Figure 1.3 shows a nested pattern of
sheet metal parts being waterjet machined. Figure 1.4 shows a
complex geometric shape cut from plate.
Figure 1.3 Waterjet machining operation. (Image courtesy of OMAX Corpo-
ration, www.omax.com.)
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Modern Metalworking Machinery, Tools, and Measuring Devices 7
Figure 1.4 Complex waterjet-machined plate. (Image courtesy of OMAX
Corporation, www.omax.com.)
1.1.3 Sheet metal parts fabrication methods
Hard dies. A die set is used to stamp out the part in flat pattern. Pro-
gressive dies also bend the part into the required shape after it is
stamped in flat pattern. This is the most common, economical method
devised to mass produce large quantities of parts to great accuracy.
Punch press. Large sheet metal parts may be made to accurate
standards using modern computer-controlled automatic multistation
punch presses. Programmers write the direct numerical control
(DNC) programs for these machines, which are then loaded into
the machine’s computer or controller. The machine operator starts
the program and stands back to watch the machine go through the
sequence of operations required to produce the finished part in flat
pattern.
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8 Chapter One
Roll forming. Flat strips of sheet metal are fed into the roll-form-
ing machine, where they progress through a set of sequenced rollers
to produce a long sheet metal part of constant cross-sectional
shape.
Hydropressing. A sheet metal flat-pattern part is placed on a set of
forming dies, being located correctly with locator pins, and is then
pressed into shape by the action of the hydropress. Many aircraft
sheet metal parts are produced in this manner. Lightening holes
and shrink flutes are produced simultaneously with the part to
control the metal along curved surfaces.
Hydraulic brakes. In this machine, a flat-pattern sheet metal part
is given flanges or webs to produce the finished part. The modern
brakes have automatic back gauges and material-handling devices
to assist the operator in making the various bends and flanges
required on the part.
Hydraulic shears. The standard hydraulic shear cuts sheet metal
according to the back gauge set by the machine operator and his or
her accuracy in placing the sheet into the machine.
1.2 Measurement and Gauging
The preceding section provided an overview of many types of metal-
working and machining processes. In a production environment,
parts typically are fabricated according to specifications on the
computer-aided design (CAD) drawing using one or more of the
aforementioned processes. At certain points during the fabrication
process, parts are inspected to verify that they satisfy the required
geometric and dimensional tolerances. In some cases, 100 percent
of the parts are inspected. In many instances, however, it is suffi-
cient to inspect a subset of parts using a statistical sampling scheme.
This section describes some of the instruments used to perform
component inspection.
1.2.1 Coordinate measuring machines (CMMs)
CMMs are highly versatile inspection machines. Although CMMs are
available in numerous configurations, the typical CMM consists of
a probe that is positioned beneath a gantry. Depending on the type
