Machining*

MACHINABILITY of copper and copper type and geometry of tool used, the cutting oper- standard test method described in ASTM E 618,
alloys can be related to the type of chips (turn- ation, the machine tool, metallurgical structure of “Standard Method for Evaluating Machining
ings) they produce during high-speed machining the tool and workpiece, the cutting/cooling fluid, Performance Using an Automatic Screw/Bar
operations, including machining in automatic and the machinist’s skill and experience. Machine.” The method calls for manufacture of
screw machines. As described in this article, the For an automatic screw machine operator, a large quantities of the standard test piece shown
machinability of copper and copper alloys is gen- definition based on some combination of produc- in Fig. 2. The test piece simulates typical screw
erally considered quite good in comparison with tion rate (the bottom-line criterion), tool wear, machine products in size, scrap ratio (the amount
other structural materials, particularly steels. and surface finish has the most practical signifi- of chips removed relative to the weight of starting
cance. Such a definition can be provided using the material), and machining operations.
Defining Machinability
Machinability can be defined in terms of
power consumption, tool wear rates, surface fin-
ish, chip morphology, or combinations of these
criteria (Ref 1). In fact, the meaning of “machin-
ability” depends on the particular needs of the
individual observer (or product).
Another difficulty in defining machinability is
that it depends on the combined influences of a
large number of factors, many of which are quite
complex. For example, machinability is certainly
closely linked to the physical and mechanical
properties of the workpiece: hard, brittle metals
being generally more difficult to machine than
soft, ductile ones (Fig. 1). But very ductile metals,
such as pure copper, stainless steels, and some
aluminum alloys tend to form long stringy chips,
which makes them troublesome to machine.
Machinability is also strongly dependent on the
1.50

1.00
Carbon and
Power required for turning, hp/in.3/min

0.80 alloy steels

0.60

Copper-base
0.40 alloys Free-cutting
steels
Cast irons

0.20
Aluminum
alloys

0.10
Magnesium alloys
0.08
30 40 60 80 100 200 400
Hardness, HB Fig. 2 Details of the ASTM E 618 machinability test specimen and the relative position of the form tools. As shown
in this figure, the standard automatic screw machine part is designed to be made from 25 mm (1 in.) diam bar
stock. The part used in the machinability tests for brasses, steels, and aluminum alloys was downsized to permit use of
Fig. 1 Influence of workpiece hardness on machinability 19 mm (0.75 in.) diam rod; this is permitted under ASTM E 618, if done for all materials.

*Portions of this article are adapted from Copper Rod Alloys for Machined Products, Copper Development Association Inc., New York, 1996. Used with permission.
 Machining / 265

The ASTM test evaluates the machinability very hard tempers, these are not conditions to Type I (Free-Cutting) Alloys
of a material by determining the effect of pro- be expected in high-speed production. For
duction rate (spindle speed and cutting tool feed mass-produced screw machine parts made
rate) on tool wear. Tool wear is measured indi- from free-cutting brass or one of the other Strictly speaking, lead-bearing copper alloys
rectly by monitoring the dimensions of the test leaded copper alloys, high-speed steel is the are composite structures rather than true alloys.
piece and surface finish, just as in commercial standard tool material. This is because lead is insoluble in copper and
machine shop practice, where tools are resharp- It is not possible to present a full series of appears as a dispersion of microscopic globules,
ened when parts go out of tolerance. The ASTM ASTM E 618-based machinability indexes in as shown in Fig. 5. The stress-raising effect of
test method makes it possible to interpolate the this article because data of the type plotted in these lead particles causes chips to break up into
production rate that provides an “optimal” Fig. 3 are not yet available for the hundreds of tiny flakes as the metal passes over the tool face.
eight-hour tool life, and that production rate is copper alloys. The conventional index ratings (This is what is meant by the term “free-cutting.”)
taken as the machinability rating of the test listed in Tables 1 and 2 for wrought and cast Careful observations have shown that chips
material (Fig. 3a). alloys, respectively, are based on allowable from leaded alloys remain in contact with the
The most important advantage of the ASTM machining speed, tool wear, finish, accuracy, tool face for only a very short time before the
E 618 method is that it permits a fair compari- and power requirements, plus a degree of sub- energy of fracture actually propels them away
son of completely different materials. Such a jective judgment. They provide a reasonable, from the cutting tool. The short contact time
comparison, particularly between free-cutting approximate guide to machinability. reduces friction, which in turn minimizes tool
brass (63Cu-3.1Pb-34.5Zn) and leaded Effect of Chip Appearance on wear and energy consumption. It has been sug-
American Iron and Steel Institute/Society of Machinability. Chip appearance is a good indi- gested that lead also acts as an “internal lubri-
Automotive Engineers (AISI/SAE) 12L14 steel, cator of the machinability of copper and copper cant” as it smears over the tool face.
has always been difficult, and the several alloys. It also relates to the microstructure of the The beneficial effect of lead on free-cutting
machinability indexes currently in use only con- material and permits categorization of copper behavior increases with lead content, but the rate
fuse the issue. When rated according to ASTM alloys in terms of reasonably similar machining of improvement decreases as lead content rises.
E 618, brass is nearly five times as machinable characteristics. Copper alloys produce three dis- Significantly improved machinability can be
as the leaded steel, meaning that if C36000 tinct types of chips: measured in leaded alloys containing less than
were assigned an index rating of 100, AISI/SAE 0.5% Pb, although optimal free-cutting behavior
12L14 would have a rating of 21. ASTM E 618- • Type I (free-cutting) alloys yield small, frag- occurs at concentrations between 0.5% and
based machinability ratings of a few common mented chips, making them well suited for 3.25% (Fig. 6). The specified nominal lead con-
screw machine feedstock metals are shown in high-speed machining. They contain lead or tent in C36000 is 3.1%.
Fig. 3(b). alternative free-cutting additives. Effects of Lead on Properties. Lead does not
• Type II (short-chip) materials, which are gen- have a significant effect on strength; however,
erally multiphase alloys, produce curled but leaded alloys can be difficult to cold work exten-
Machinability of Copper Alloys brittle turnings. sively. The effect becomes more pronounced as
lead content rises; therefore alloys such as
All copper alloys are machinable in the • Type III (long-chip) materials, which are usu-
C34500 and C35300, which have lower lead
ally single-phase alloys, produce long and
sense that they can be cut with standard contents than C36000, may be better choices for
continuous chips that are often tightly curled.
machine tooling. High-speed steel suffices for products that require both high-speed machining
all but the hardest alloys. Carbide tooling can Examples of the three types of chips are shown and extensive cold deformation.
be used but is rarely necessary, and while in Fig. 4. How these chip characteristics influ- Other detrimental effects of lead include an
grinding may be required for a few alloys in ence machinability is addressed subsequently. impairment in welding and brazing properties.

120

C36000
6000 100

4000 C36000/M2
80
Production rate, pieces/h

C46400/M2 C34000/M2
Machinability index

C34000
2000 C36000/A2 60
C46400 2011-T3
C34000/A2
40
1000
800 1213/M2
12L14/M2 12L14
600 20

400 1213\A2 12L14\A2

0
1 2 4 8 10 20
Workpiece materials
Form tool life, h
LIVE GRAPH
(a) Click here to view (b)

Fig. 3 Results of a universal machinability index test for various alloys. (a) Tool life data plotted to determine the maximum theoretical production rate for an 8 h tool life. This value
of production rate is taken as the machinability rating of the material under test. (b) Universal machinability ratings (maximum theoretical production rates for 8 h M2 tool
life) of common automatic screw machine materials using ASTM E 618. Data are normalized to alloy C36000 (free-cutting brass 100). Source: Ref 2
266 / Fabrication and Finishing

Lead may cause related problems in products duce free-cutting behavior in copper alloys. These ing components have traditionally been made
such as welding electrodes and cutting torch elements can be more effective than lead in terms from leaded red or semi-red brasses that not
tips, which operate at high temperatures. of the amounts needed to produce optimal longer meet the lead content restrictions estab-
Lead causes no significant changes in the cor- improvements, but they are not without short- lished by the Environmental Protection Agency or
rosion behavior of an alloy, but trace quantities comings. Bismuth and tellurium can cause seri- the National Sanitation Foundation. This has led
can be dissolved from machined surfaces by suf- ous embrittlement and/or directionally sensitive to the development of low-lead red brass casting
ficiently aggressive media, including some ductility when present in uncontrolled concentra- alloys containing bismuth and selenium.
potable waters. If lead exposure is a problem, tions, while sulfur cannot be used in many alloy Examples include C89510 and C89520, which
wetted surfaces can be protected with electro- systems because of its reactivity. Generally, contain between 0.5 and 2.2% Bi and 0.35 to
plated or organic coatings. Surface lead can also unleaded free-cutting alloys are considerably 1.1% Se (Bi:Se ratio ≥2:1). These alloys have
be removed by a relatively simple etching more expensive than leaded versions and there- machinability ratings between 75 and 85 (C36000
process that leaves nothing but “pure” brass fore should be considered only when lead must be 100). Selenium enhances the effect of bismuth
exposed to the environment. avoided entirely. Such is the case with plumbing in red brasses; therefore, it reduces the amount of
Alternative Free-Cutting Additives. Addi- fixtures, which have strict regulations regarding bismuth needed to improve machinability and
tions of tellurium, sulfur, and bismuth also pro- lead contents. Sand-cast faucets and other plumb- lessens the chances of embrittlement.

Table 1 Machinability ratings of wrought copper alloys

Machinability Machinability
UNS No. Alloy name index rating UNS No. Alloy name index rating
Type I: free-cutting copper alloys for screw machine production (suitable for automatic Type III: long-chip copper alloys. (Usually single phase alloys. Stringy or tangled chips,
machining at the highest available cutting speeds) somewhat “gummy” behavior. Not for screw machine work.)
C36000 Free-cutting brass 100 C63200 Nickel-aluminum bronze, 9% 40
C35600 Extra-high-leaded brass 100 C22600 Jewelry bronze, 871/2% 30
C32000 Leaded red brass 90 C23000 Red brass, 85% 30
C34200 High-leaded brass, 641/2% 90 C24000 Low brass, 80% 30
C35300 High-leaded brass, 62% 90 C26000 Cartridge brass, 70% 30
C35330 Arsenical free-cutting brass 90 C26130 Arsenical cartridge brass, 70% 30
C38500 Architectural bronze 90 C26800 Yellow brass, 66% 30
C14500 Tellurium-bearing copper 85 C27000 Yellow brass, 65% 30
C14520 Phosphorus deoxidized, 85 C61000, C61300, Aluminum bronzes, 7% 30
tellurium-bearing copper C61400
C14700 Sulfur-bearing copper 85 C65100 Low silicon bronze B 30
C18700 Leaded copper 85 C65500 High silicon bronze A 30
C31400 Leaded commercial bronze 80 C65600 Silicon bronze 30
C31600 Leaded commercial bronze 80 C67000 Manganese bronze B 30
(nickel-bearing) C10100 Oxygen-free electronic copper 20
C34500 Leaded brass 80 C10200 Oxygen-free copper 20
C37700 Forging brass 80 C10300 Oxygen-free extra low phosphorus copper 20
C54400 Phosphor bronze, B-2 80 C10400, C10500, Oxygen-free coppers with silver 20
C19100 Nickel copper with tellurium 75 C10700
C19150 Leaded nickel copper 75 C10800 Oxygen-free low phosphorus copper 20
C34000 Medium-leaded brass, 64 /2%
1 70 C11000 Electrolytic tough pitch copper 20
C35000 Medium-leaded brass, 62% 70 C11300, C11400, Tough pitch coppers with silver 20
C37000 Free-cutting Muntz metal 70 C11500, C11600
C48500 Naval brass, high-leaded 70 C12000 Phosphorus-deoxidized, low-residual 20
C67300 Leaded silicon-manganese bronze 70 phosphorus copper
C69710 Leaded arsenical silicon red brass 70 C12100 Phosphorus-deoxidized, low-residual 20
C17300 Leaded beryllium copper 60 phosphorus copper
C33500 Low-leaded brass 60 C12200 Phosphorus-deoxidized, high-residual 20
C67600 Leaded manganese bronze 60 phosphorus copper
C48200 Naval brass, medium-leaded 50 C12900 Fire-refined tough pitch copper with silver 20
C66100 Leaded silicon bronze 50 C15000 Zirconium copper 20
C79200 Leaded nickel silver, 12% 50 C16200 Cadmium copper 20
C16500 Cadmium-tin copper 20
Type II: short-chip copper alloys. (Usually multiphase alloys. Short, curled or serrated
C18000 Nickel-chromium-silicon copper 20
chips. Screw machine production depends on type of cutting operation.)
C18100 Chromium-zirconium-magnesium copper 20
C64200 Arsenical silicon-aluminum bronze 60 C18135 Chromium-cadmium copper 20
C62300 Aluminum bronze, 9% 50 C18150 Chromium-zirconium copper 20
C62400 Aluminum bronze, 101/2% 50 C18200, C18400 Chromium coppers 20
C17410, C17500, Beryllium coppers 40 C21000 Gilding, 95% 20
C17510 C22000 Commercial bronze, 90% 20
C28000 Muntz metal, 60% 40 C50700 Tin (signal) bronze 20
C61800 Aluminum bronze, 10% 40 C51000 Phosphor bronze, 5% A 20
C63000 Nickel-aluminum bronze, 10% 40 C52100 Phosphor bronze, 8% B-2 20
C63020 Nickel-aluminum bronze, 11% 40 C61000 Aluminum bronze, 7% 20
C63200 Nickel-aluminum bronze 40 C64700 Silicon-bronze 20
C46200 Naval brass, 631/2% 30 C70600 Copper-nickel, 10% 20
C46400 Naval brass, uninhibited 30 C71500 Copper-nickel, 30% 20
C67400 Silicon-manganese-aluminum brass 30 C74500 Nickel silver, 65-10 20
C67500 Manganese bronze A 30 C75200 Nickel silver, 65-18 20
C69400 Silicon red brass 30 C75400 Nickel silver, 65-15 20
C69430 Arsenical silicon red brass 30 C75700 Nickel silver, 65-12 20
C15715, C15725, Aluminum oxide dispersion-strengthened 20
C15760 coppers
C17000 Beryllium copper 20
C17200 Beryllium copper 20
C62500 Aluminum bronze, 13% 20

Source: Ref 1
 Machining / 267

Table 2 Machinability ratings of copper

casting alloys
UNS No. Alloy name Machinability

Type I free-cutting alloys

C83600 Leaded red brass 90
C83800 Leaded red brass 90
C84400 Leaded semi-red brass 90
C84800 Leaded semi-red brass 90
C94320 High-leaded tin bronze 90
C93700 High-leaded tin bronze 80
C93720 High-leaded tin bronze 80
C85200 Leaded yellow brass 80
C85310 Leaded yellow brass 80
C93400 High-leaded tin bronze 70
C93200 High-leaded tin bronze 70
C97300 Leaded nickel brass 70
Type II short-chip alloys (moderately machinable)
C83500 Leaded tin bronze 60
C83520 Leaded tin bronze 60 Fig. 4 Broken chips typical of free-cutting brass, type I (center), flanked by type II, short-chip turnings (right), and type
III, long-chip turnings (left)
C86500 Leaded high-strength 60
manganese bronze
C63380 Silicon-aluminum bronze 50
C64200 Silicon-aluminum bronze 50
C90500 Tin bronze 50
C90300 Tin bronze 50
C95300 Aluminum bronze 35
C61800 High-strength manganese 30
bronze
C67000 High-strength manganese 30
bronze
… Beryllium bronze 20–40
Fig. 6 Effect of lead content on the machinability of
Type III long-chip alloys (less easy to machine) yellow brass
C86100 High-strength manganese bronze20
C95200 Aluminum bronze 20 modate up to 9% Al and remain homogeneous.
C95400 Aluminum bronze 20 The equilibrium room temperature solubility
C95500 Aluminum bronze 20
limit for tin in copper is quite low, near 1% by
Note: Additional machinability ratings for copper casting alloys can be weight, but wrought copper-tin alloys (tin
found in the article “Cast Copper and Copper Alloys” in this Handbook. bronzes), which are heated during processing,
Source: Ref 3
remain structurally homogeneous up to almost
15% Sn because the transformation that pro-
Type II (Short-Chip) Alloys duces the second phase is rather sluggish.
Copper-nickel alloys have homogeneous alpha
Two or more phases may appear in the structures no matter how much nickel is present.
microstructure when alloy concentration is suffi- Type III copper alloys are soft and ductile in
ciently high (for example, high-zinc brasses con- the annealed state. Their mechanical properties
taining both alpha and beta phases). Beta makes are governed by alloying and the degree of cold
cold work more difficult, but it improves the work. Pure copper can be strengthened only by
capacity for hot deformation considerably. cold working; whereas, the strength of single-
Heterogeneous (two or more phases) type II Fig. 5 Microstructure of alloy C36000 (free-cutting phase brasses, bronzes, aluminum bronzes, and
brass) showing globules of lead (dark) and alpha
alloys tend to be stronger than single-phase mate- grains (light). 270 copper-nickels derives from the combined
rials, but ductility is correspondingly reduced. effects of cold work and alloying.
Figure 4 (right side) shows turnings from a important than tool wear or chip management, Even highly alloyed single-phase alloys retain
multiphase type II alloy. As the metal passes both of which are less favorable in type III a considerable degree of ductility, as can be seen
over the cutting tool, it tends to shear laterally in alloys. Type II alloys are often processed on in their turnings. Figure 4 (left side) shows the
a series of closely spaced steps, producing automatic screw machines, although production long, stringy chips typical of type III alloys. The
ridges on the short, helical chips. This intermit- rates are considerably lower than those attain- smooth and uniform chip surface reflects the
tent shear process raises the potential for tool able with free-cutting alloys. uninterrupted passage of the cutting tool. The
chatter and poor surface quality, but these prob- chip is thicker than the feed rate because the
lems can be avoided by adjusting machining Type III (Long-Chip) Alloys copper is upset as it passes over the face of the
parameters appropriately. Chip breakers can be tool. The accompanying cold work makes the
used to reduce the length of the coiled turnings. The simplest copper alloys are those with chip hard and springy, but it also consumes ener-
The machinability of type II alloys depends on essentially uniform microstructures. In pure gy that, converted to heat in the chip and cutting
the complex relationships between alloy copper, the structure contains only one phase, or tool, increases tool wear.
microstructure and mechanical properties. Power crystal form, commonly designated alpha. This The machinability of type III alloys therefore
consumption varies with mechanical properties single-phase structure is retained within fairly can be related to the following factors:
and work hardening rate, while the shape of the broad limits when alloying elements are added,
turnings depends on the ductility of the metal. but the alloy content at which additional phases • Initial hardness, either from prior cold work
In part because of their relatively manageable begin to appear differs with the individual alloy- or alloy content. Soft materials generally con-
chips, multiphase alloys are considered to have ing element and with processing conditions. sume less energy than harder alloys, and other
better machinabilities than ductile type III met- For example, up to approximately 39% Zn factors aside, produce less tool wear. On the
als. The higher power consumption for the hard- can be added to copper to form a single-phase other hand, softer materials tend to deflect
er type II alloys is generally taken as being less alpha brass. The alpha structure can also accom- under the pressure of the cutting tool, reduc-
268 / Fabrication and Finishing

ing dimensional accuracy. Improperly ground tortion effects caused by the slight (0.5%) volume in such cases is free-cutting brass. Other free-
tools have a tendency to dig into such metals, change that occurs during heat treatment. cutting alloys are specified when the electrical,
leading to chatter and poor surface finish. chemical, or mechanical property requirements
• Work hardening rate, as a function of defor- of the product exclude brass.
mation. A high work hardening rate results Selecting Copper Screw machine parts that require severe cold
in high energy consumption, hard chips, Alloys for Machinability deformation, as in deep knurling or coarse-
and high tool wear. Severely work-hardened rolled threads, may require an alloy with a
chips can tear away from the underlying It is difficult to assign machinability ratings reduced lead content. Candidates include
soft matrix, causing smearing and poor sur- unambiguously since machinability itself can C34000 (medium-leaded brass, 6412%), C34500
face finish. have several meanings. All ranking systems (high-leaded brass) and C35300 (high-leaded
• Chip appearance. Although the type III met- therefore have strengths and weaknesses brass, 62%), all of which contain 2% Pb.
als are machinable, their tendency to form depending on the individual observer’s needs. Type II alloys can be used with automatic
long, stringy chips makes them less than Tables 1 and 2 group the copper alloys in three tooling, although production rates will be signif-
ideal candidates for high-speed production on broad categories. Note that the groups are relat- icantly lower than with free-cutting alloys. The
automatic screw machines, where clearing ed to the manner of chip formation described curly-chip alloys have a tendency to produce
chip tangles may cause difficulty. earlier. Note also that there is a considerable dif- chatter, with resulting degradation in surface fin-
ference in machinability between the free-cut- ish, unless the tool and workpiece are rigidly
There is a considerable range in machining
ting compositions, type I alloys, and metals that supported. If proper care is exercised, the alloys
performance among alloys in this group. Soft
exhibit types II and III behavior. are readily machinable.
coppers and brasses machine quite readily, while
Differences among metals within the groups, Although the type III alloys can be cut rela-
high-strength alloys may require carbide tool-
especially the latter two, are relatively small. tively easily, they are considered less machin-
ing, grinding, and in a few cases, heat treatment
This is another way of saying that when materi- able than other alloy types because of the more
for optimal manufacture.
als selection is based on factors other than free- rapid tool wear they generate and because of
cutting behavior, machinability assumes less their tendency to form long, stringy chips.
critical importance. Attaining fine surface finishes also requires
Additional Factors Products manufactured on automatic screw greater attention to cutting conditions than it
Affecting Machinability machines and other high-speed machine tools does with other alloys. Since the metals are used
are usually specified in free-cutting grades to for reasons other than high-speed machining
Grain Size. Finer grain sizes are generally maximize cutting speeds and avoid chip clear- characteristics, these factors do not have an
beneficial to mechanical properties, finer- ance problems. The most common choice by far overriding effect on alloy selection.
grained metals being stronger and more ductile
than those with coarse structures. These benefits
extend to machinability. The effect is more pro- End cutting-edge End cutting-edge
nounced in leaded multiphase alloys, although angle: see note angle: see note
some improvement in machinability can be
observed in fine-grained type III alloys as well. 10 to 15° 10 to 15°
Texture. The grain structure in wrought, side cutting angle side cutting angle
rolled, or extruded metals will reflect the direc-
tion of deformation. That is, the grains of the 0° back rake 5 to 10° back rake
metals, grain boundaries, and second phases, if
any, tend to become elongated in the direction of
hot or cold work, leading to the familiar fibrous 0 to 3° 5 to 10°
texture of heavily wrought metals. side rake side rake
Since any nonuniformity in the structure of a
0 to 5°
metal can influence chip behavior, and therefore side clearance
6° end clearance 5 to 10° 6 to 15°
machining properties, it is understandable that side clearance end clearance
machinability is somewhat enhanced in cutting
directions that cross the direction of deformation. Type I free-cutting alloys Type II short-chip alloys
For example, rods and bars machine better cir-
cumferentially than longitudinally; plates machine
better in the transverse or through-thickness direc- End cutting-edge
tion than parallel to the rolling direction. angle: see note
Temper. Mechanical properties affect cutting
power requirements. Generally, the harder the 15° lead angle Note: A 19 to 5° cutting edge angle should prove
metal the higher the power needed. In most satisfactory for most rough and finish turning operations.
When the end cutting edge of a finishing tool is ground
cases, however, the economic effect of temper
parallel with the axis, considerably heavier feeds may
on attainable cutting speed and surface finish is 10 to 20° back rake be employed on light finishing cuts. Tools should be
more important than power consumption. It has ground and set so that the tool point is on center with
already been pointed out that soft, annealed tem- the effective rake angles in correct relation to the center
pers can cause galling and smearing. This is line of the work.
especially true of type III alloys and is one rea- 20 to 30°
side rake
son such metals are often machined in a slightly 10° to 15°
10 to 20°
cold-worked condition. side clearance front clearance
Heat Treatment. Beryllium coppers are rough-
machined best in the solution annealed state, then
heat treated to full hardness before finish machin- Type III long-chip alloys
ing, or if necessary, grinding. Not only does this
produce better results, it also avoids potential dis- Fig. 7 Carbon and high-speed steel turning tools used for copper and copper alloys. Source: Ref 1
 Machining / 269

Recommended Machining Practices Form tools should be ground with a front clear- tooling is used in place of the more common
ance angle between 7 and 12° (Fig. 10). high-speed steel. Recommended conditions are
Corresponding angles for carbide tools are given listed in Table 3.
The conditions recommended in this section
in Fig. 8 and 10. Cutting Fluids. Because of the “sticky” nature
for type I, II, and III alloys should only be used
Excessive clearance angles reduce tool support of the alloys, it is important to use cutting fluids
as starting points from which to optimize a
and, when combined with large rake angles, pro- that provide both good lubrication and efficient
machining operation. The machining conditions
duce a fragile, chisel-like cutting edge. It is there- cooling. Mineral oils augmented with 10 to 20%
used with a given copper or copper alloy—
fore best to begin with intermediate clearance lard oil are generally satisfactory. Sulfurized cut-
speed, feed, tool geometry, and lubricant—will
angles, adjusting them up or down, as necessary. ting fluids help prevent sticking in soft copper
be determined by the needs of the individual job,
The type III long-chip alloys require some- and copper-nickels, but they may stain freshly
the condition of the machine, and the skill of the
what lower cutting speeds and feed rates than machined surfaces if not removed quickly.
machinist/operator.
type I and II copper-base materials, although Type II (Short-Chip) Alloys. The materials
speeds can be increased significantly if carbide within this group display a wide range of
Single-Point and Form Turning
End cutting-edge End cutting-edge
angle: 8 to 15° angle: 8 to 15°
Type III (Long-Chip) Alloys. The long, con-
tinuous turnings generated from unleaded, sin- 10 to 15° 10 to 15°
gle-phase alloys deform and work harden as they lead angle lead angle
(or to suit)
pass over the cutting tool. The deformation gen- (or to suit)
erates heat and increases tool wear. Both of these
effects can be minimized by providing generous
0° back rake 0 to 5° back rake
rake angles to ease the chip off the tool face.
Single-point tools should be ground with a back 2 to 6°
rake of 10 to 20° and a side rake of as much as side rake
4 to 6°
20 to 30° (see Fig. 7 and 8 for a description of side rake
the machining terminology used in this article).
Steep rake angles should be used with cau- 4 to 6° 4 to 6° 4 to 8° 4 to 8°
tion, however, because they tend to force the tool side clearance front clearance side clearance front clearance
into the work, and the tearing action this pro-
Type I free-cutting alloys Type II short-chip alloys
duces leads to poor surface finishes. The effect is
particularly noticeable with nonrigid setups and
on machines with worn spindles or slides, that
End cutting-edge
is, conditions that encourage chatter. angle 8 to 15°
Rake angles can be reduced somewhat with
single-point carbide tools and with either dove- 10 to 15°
Note: Rake angles are based on the
tail or circular form tools (Fig. 9 and 10). In all lead angle
tool shank being set parallel with the
cases, finely polished or burnished cutting sur- (or to suit)
center line of the work and with the
faces will reduce friction and heat buildup. tool point on center. Placing the tool
Coppers and copper-nickels tend to build up 4 to 8° back rake
point above or below center will
(weld) on the cutting tool. Built-up particles can change the effective rake angles
appreciably, particularly on work of
break away and jam between the tool and work-
small diameter. On a setup where
piece, damaging the surface finish. Burnishing the tool holder is not parallel with the
the cutting tool face to a smooth finish helps 15 to 25° center line, the rake angles should be
reduce sticking, as does the application of low- side rake ground so that when the tool is
friction coatings such as titanium nitride. 7 to 10° 7 to 10° mounted, they are in correct relation.
For single-point high-speed steel tools, a front side clearance front clearance
clearance of from 10 to 15° and a side clearance
of 10 to 20° is sufficient to permit loose particles Type III long-chip alloys
to escape (Fig. 7). Smaller clearances can be tol-
erated in single-phase brasses and bronzes. Fig. 8 Carbide turning tools for copper and copper alloys

Fig. 9 Design of straight-blade and circular cutoff tools for turning copper and copper alloys. Source: Ref 1
270 / Fabrication and Finishing

Fig. 10 Design of circular and dovetail form tools for turning copper and copper alloys. Source: Ref 1

Table 3 Turning data applicable to single-point and form tools for copper alloys
For single-point tools only
Side relief Front relief Back rake Side rake Surface speed Roughing feed Finishing feed
Tool material angle, degrees angle, degrees angle, degrees angle, degrees m/min sfm m/rev mil/rev m/rev mil/rev

Free-cutting type I alloys

HSS(a) 0–5 6 0–5 0–3 92–305 300–1000 51–381 2–15 51–76 2–3
Carbide 4–6 4–6 0 2–6 152–488 500–1600 51–381 2–15 51–76 2–3
Short-chip type II alloys
HSS(a) 5–10 6–15 5–10 5–10 46–92 150–300 51–203 2–8 51–76 2–3
Carbide 4–8 4–8 0–5 4–8 122–183 400–600 51–203 2–8 51–76 2–3
Long-chip type III alloys
HSS(a) 10–20 10–15 10–20 20–30 23–46 75–150 51–203 2–8 51–76 2–3
Carbide 7–10 7–10 4–8 15–25 92–152 300–500 51–203 2–8 51–76 2–3

(a) HSS, M2 high-speed steel. Source: Ref 1

strength and ductility, and cutting conditions Cutting fluids should match the workpiece brass. Recommended cutting speeds for leaded
must be adjusted accordingly. At one end of material. Alloys with machinability ratings sim- copper metals other than free-cutting brass range
the spectrum are the ductile, high-zinc brasses, ilar to high-strength long-chip alloys require a from 91 to 305 m/min (300–1000 sfm).
which can be cut using conditions approaching cutting fluid that provides effective lubrication Cutting Fluids. Straight light mineral oils are
those used with high-strength long-chip as well as effective cooling. For these, a mineral generally preferred as cutting fluids for the free-
alloys, that is, rake angles up to 10° and rea- oil fortified with between 5 and 15% lard oil or cutting alloys. Soluble oils also give good results.
sonably generous clearance. The less ductile a sulfurized fatty-oil base thinned with a light
grades of phosphor and aluminum bronze mineral oil will give good lubrication. The alloys
should be cut using little or no rake, because in this group that have relatively high machin- Milling
the duplex structure of these metals makes ability ratings can be cut satisfactorily using sol-
them prone to chatter. uble oils. Type III (Long-Chip) Alloys. The chip clear-
Cutting speeds between 46 and 92 m/min Type I (Free-Cutting) Alloys. These materi- ance problems these ductile metals present dur-
(150 and 300 sfm) are recommended for single- als require little or no rake since chips tend to ing milling are similar to those encountered dur-
point or form cutting with high-speed steel; break up almost immediately after they form. ing turning. Milling cutters with tooth spacings
speeds can be increased to between 122 and 183 Modest clearance angles up to 5° can be used but no finer than four to eight teeth per inch will
m/min (400 and 600 sfm) with carbide tooling. are not necessary unless the tool tends to drag. facilitate chip removal. Combined cutters can
Optimal feed rates should be determined by Free-cutting brass, C36000, can be cut at the also be used, but teeth should be interlocked to
beginning with a fairly light cut, approximately maximum attainable speed. In fact, in the range of prevent chips from collecting between cutter
0.05 mm/rev (0.002 in./rev), increasing this diameters normally encountered in screw machine elements. Spiral cutters are useful for wide cuts;
gradually until surface finish and/or tool wear products, there are no commercially available helix angles as large as 53° have been found to
rates deteriorate. machine tools that exceed the speed capacity of be satisfactory for cutting copper.
 Machining / 271

moderate milling conditions. Recommended tool

geometries are listed in Table 4.

Drilling
Most copper alloys can be drilled with stan-
dard twist drills, although high-production con-
ditions usually call for special drill configura-
tions. Some authorities claim that ductile alloys
perform better with fast-twist drills, while others
hold that moderate or slow twists are better able
to clear long, stringy chips. There is general
agreement that small-diameter holes in copper
are best cut with fast-twist drills. Free-cutting
grades, including C36000, can be drilled very
rapidly with straight-fluted brass drills, which
permit easy escape for the tiny fragmented chips
of the alloys.
Fig. 11 Milling cutter used for copper and copper alloys. Source: Ref 1
Full rake angles are normally retained in drills
used on long-chip copper alloys. Drill-tip angles
should be between 100 and 110°, and lip clear-
Table 4 Milling data for copper alloys ance angles may have to be as steep as 20° (Fig.
Land Surface speed 12). Notching the cutting edge helps break up
Rake angle, Clearance angle,
Workpiece material degrees degrees mm in. m/min sfm long, stringy turnings. Drills for short-chip and
Free-cutting type I alloys 0–10 10–15 0.38–0.76 0.015–0.030 61–152 200–500
free-cutting alloys should be flat-ground to a 0°
Short-chip type II alloys 0–10 5–15 0.38–0.76 0.015–0.030 46–61 150–200 rake. Standard 118° tip angles should be used;
Long-chip type III alloys 0–15 5–15 0.38–0.76 0.015–0.030 15–46 50–150 lip clearance can range from 12 to 15° (Fig. 12).
Recommended speeds are similar to those
Source: Ref 1
used for turning operations, meaning that small-
diameter holes can usually be drilled at the max-
imum possible spindle speed. Feed rates should
Generous rake angles and adequate clearance alloys, but optimal conditions must be selected
range between 0.05 and 0.76 mm/rev (0.002 and
should be provided on face-, side-, and end- for each alloy. Small-diameter cutters should be
0.030 in./rev), depending on alloy type. Readily
milling cutters to prevent burnishing of the ground with radial teeth (0° rake) for hard alu-
machinable brasses and free-cutting alloys drill
workpiece. Up to 15° clearance can be incorpo- minum bronzes.
best with high feeds, while ductile coppers and
rated on tooth sides in side and face cutters and Recommended milling speeds for these alloys
long-chip alloys fare better with lighter feeds.
on tooth ends in end cutters (Fig. 11). A radial can be as high as 61 m/min (200 sfm).
Cutting fluids are beneficial but not absolute-
undercut will prevent tooth edges from dragging Recommended feeds range from 0.4 to 0.56
ly necessary when drilling highly machinable
along the workpiece. Cutting edges should be mm/rev (0.016–0.022 in./rev) per tooth for spiral
free-cutting alloys; they are, however, required
finely polished and/or coated to reduce loading. cutters and from 0.25 to 0.56 mm/rev
for other compositions.
Recommended milling speeds range from 15 (0.010–0.022 in./rev) per tooth for end mills.
to 45 m/min (50–150 sfm), although consider- Soluble-oil coolants are satisfactory for these
ably higher speeds can be used. Feed rates alloys. Mineral oils containing about 5% lard oil Boring
range from 0.18 to 0.76 mm/rev (0.007–0.030 can also be used.
in./rev) depending on the type of cutter. Type I (Free-Cutting) Alloys. These alloys can Tool geometry is most important in boring in
Recommended milling conditions are listed in be milled at speeds up to 152 m/min (500 sfm). As order to achieve the required smooth finished
Table 4. with turning operations, carbide tooling permits surface and to direct chip flow away from the cut
Type II (Short-Chip) Alloys. As with turning the highest cutting speeds. Cutting fluids are gen- surface. Tools for boring copper alloys are
operations, rake angles should generally be erally necessary at high speeds and feeds, primari- shown in Fig. 13; relevant machining data are
reduced from those used with ductile long-chip ly for heat removal, but are often not used under presented in Table 5.

Reaming
Fluted reamers used with copper alloys are
similar to those used with steel, except that

Table 5 Boring data for copper alloys

using carbide tooling
Back rake Side rake
Speed
angle, angle,
Workpiece material degrees degrees m/min sfm

Free-cutting 0 5 152–305 500–1000

type I alloys
Short-chip 0–5 5–10 122–183 400–600
type II alloys
Long-chip 5–10 15–20 61–152 200–500
type III alloys

Source: Ref 1
Fig. 12 Drill point and clearance angles for twist drills. Source: Ref 1
272 / Fabrication and Finishing

clearances should be increased to 8 to 10°. All recommended feeds and depths of cut for holes tions permit, threading should be performed
types of reamers can be used; however, fluted up to 25 mm (1 in.) in diameter. with alloys in the softest available temper.
reamers are less prone to chatter, an important Thread die cutting generally follows the rec-
consideration with tough short-chip alloys. A ommendations for turning operations: soft, duc-
rake angle (hook) of 5° is used on all copper Threading and Tapping tile long-chip alloys require large rake angles
alloys except free-cutting leaded compositions, (17–25°, and up to 30° for pure copper); hard
which are generally reamed with zero or nega- Free-cutting brass accepts fine- to medium- multiphase alloys such as tin bronzes and high-
tive rake (Fig. 14). It is important that cutting pitch rolled threads quite well; however, coarse strength yellow brasses require intermediate
tools be lapped to a fine surface finish. or deep threads may call for alloys such as medi- rake angles (generally 12–17°, but up to 25° for
Copper and long-chip metals should be um-leaded brass, C34000, or the high-leaded high-strength aluminum bronzes). Free-cutting
reamed at a speed of 12 to 27 m/min (40–90 brasses C34500 and C35300, which have some- brass and highly leaded tin bronzes require zero
sfm); short-chip alloys at 23 to 46 m/min what lower lead contents than C36000 and are rake. Tools for threading and tapping are shown
(75–150 sfm); and free-cutting leaded alloys at therefore more ductile. The ductile unleaded in Fig. 15 and 16.
30 to 61 m/min (100–200 sfm). Table 6 gives copper alloys can also be roll threaded. If condi- Table 7 lists recommended rake angles and
chamfers for taps used with the copper metals.
No back rake No side rake Refer to Fig. 16 for descriptions of the terms
used. Threading and tapping speeds are listed in
Side Table 8, while tool geometries for tap and die
Feed Back cutting chasers and circular chasers are given in Tables
Bore relief angle Cutting angle cutting angle 9 and 10, respectively.
(end clearance angle) angle
Nose
Additional bore Lip angle (end
angle
Clearance angle Positive
cutting Sawing (Ref 3)
angle)
Work diameter side rake Rotation
Selection of the proper width of saw, number
of teeth, pressure, feed, and speed is as important
as the condition of the machine involved. Width
True rake angle of the hacksaw or bandsaw blade is usually gov-
Positive back rake
Feed erned by type of equipment. It is advisable that
C
L the blade be wide enough to withstand normal
Positive feeding pressures. Correct tension is vital. A
side rake Lead
Lead angle clearance loose blade will cause crooked cuts, buckling,
to work Nose angle and twisting as well as stripped teeth. Too great a
(side relief) tension will also cause snapping and throw too
great a load on guides and the machine itself.
Positive back rake Feeding pressure should be determined by size
and machinability of the alloy. On gravity- or
Fig. 13 Design of boring tools used for copper alloys. Source: Ref 1
hand-fed bandsaw machines, moderate feed is
desirable on small sections or readily machined
alloys. Increased pressure is recommended on
heavy sections or alloys with low machinability
ratings to reduce saw wear. Modern power hack-
saw machines employ either mechanical or
hydraulic feeds, permitting increased feed setting
on small sections of soft alloys. Large sections
and hard alloys require reduced feed settings.
Correct tooth specification is important to per-
mit adequate chip clearance. Coarse teeth are
desirable on soft or thick material and finer teeth
are indicated on thin sections or hard alloys. Care
must be taken to ensure correct set. If the set is
worn to any great extent, crooked cuts and exces-
sive heat with subsequent saw failure will result.
Solid and inserted tooth shapes for circular saws
are shown in Fig. 17; relevant circular sawing data
are given in Table 11. For band sawing of copper
alloys, blades of 13 or 19 mm (0.5 or 0.75 in.)
Fig. 14 Reamer angles and clearances. Source: Ref 1
width are most commonly used, and only for short
radius cutting should narrow blades be used. The
Table 6 Reaming data for copper alloys using high-speed steel tooling
Feed Table 7 Tapping data for copper alloys
Hole diameter Copper Brass and bronze Depth of cut Tap rake Die chamfer,
mm in. mm/rev in./rev mm/rev in./rev mm in. Workpiece material angle, degrees degrees

3.2 1/8 0.15 0.006 0.25 0.010 0.08–0.10 0.003–0.004 Free-cutting type I alloys 2–4 10–30(a)
3.2–9.5 1/8 3/8 0.15–0.25 0.006–0.010 0.25–0.41 0.010–0.016 0.08–0.18 0.004–0.007 Short-chip type II alloys 5–8 10–15(a)
9.5 3/8 0.23–0.61 0.009–0.024 0.41–0.91 0.016–0.036 0.18–0.38 0.007–0.015 Long-chip type III alloys 8–10 10–15(a)

Source: Ref 1 (a) Two or three threads. Source: Ref 1

 Machining / 273

Table 8 Threading and tapping Table 9 Tool geometry for tap Table 10 Tool geometry for
speeds for copper alloys using and die chasers circular chasers
high-speed steel tooling Tap Die Rake Face Throat
Lineal threading angle, angle, angle, Clearance,
Rake Throat Rake Throat
Workpiece material degrees degrees degrees degrees
or tapping speed(a) angle, angle, angle, angle,
Workpiece material m/min sfm Workpiece material degrees degrees degrees degrees Free-cutting –5 to 5 0 25 12
Free-cutting –5 to 5 15 –10 to 0 15 type I alloys
Free-cutting type I alloys 30–61 100–200 Short-chip 10–20 1–2 25 12
Short-chip type II alloys 15–27 50–90 type I alloys
Short-chip 5–12 20 1–10 20 type II alloys
Long-chip type III alloys 12–15 40–50 Long-chip 15–35 2–3 25 12
type II alloys
Long-chip 15–25 30 12–30 30 type III alloys
(a) Recommended cutting speeds are for moderate-pitch threads. Use
speeds in the lower ranges for coarse threads. Source: Ref 1 type III alloys
Source: Ref 1
Source: Ref 1

Fig. 15 Threading tap design used for copper and copper alloys. Source: Ref 1 Fig. 16 Chasers for die heads and collapsible taps. Source: Ref 1

Table 11 Circular sawing data for copper alloys

Chromium
Hook plated to Hollow ground
Machin- Tooth Diameter Thickness Number angle, Rim speed Feed Coolant, Hardness 0.05 mm taper
ability(a) type(b) mm in. mm in. of teeth degrees m/min sfm mm/min in./min lubricant HRC (0.002 in.) per mm per in.
Rod, 38 mm ( 11/2 in.)
I SST(c) 305 12 2.4 3/32 150–200 10–15 1220–2440 4000–8000 1524 60 Grease stick 52–56 Yes 0.09 0.0035
II TST(c) 305 12 2.4 3/32 100–125 10–15 1219–1524 4000–5000 762 30 Grease stick 52–56 Yes 0.09 0.0035
III Ins. SST 305 12 3.2 1/8 75–100 5–10 610–914 2000–3000 508–762 20–30 Grease stick 60–62 No 0.025 0.0010
Rod, 38–102 mm (11/2–4 in.)
I Ins. Alt. SST 406 16 4.8 3/16 60–64 10–15 305 1000 762–1016 30–40 Compound(d) 64–66 No 0.09 0.0035
& BST
II Ins. Alt. SST 406 16 4.8 3/16 60–64 10–15 305 1000 508–762 20–30 Compound(d) 62–64 No 0.025 0.0010
& BST
III Ins. Alt. SST 406 16 6.3 1/4 60–64 5–10 229 750 254–508 10–20 Compound(d) 62–64 No 0.025 0.0010
& BST
Rod, 102–204 mm (4–8 in.)
I Ins. Alt. SST 711 28 6.3 1/4 60–80 10–15 183–229 600–750 508–762 20–30 Compound(d) 62–64 No 0.025 0.0010
& BST
II Ins. Alt. SST 711 28 6.3 1/4 60–80 10–15 183–229 600–750 381–635 15–25 Compound(d) 62–64 No 0.025 0.0010
& BST
III Ins. Alt. SST 711 28 6.3 1/4 60–80 5–10 152–198 500–650 254–381 10–15 Compound(d) 62–64 No 0.025 0.0010
& BST

(a) Machinability: I, free-cutting; II, short-chip; III, long-chip. (b) SST, standard square tooth; TST, topped square tooth; BST, bevel standard tooth; Ins., inserted; Alt., alternating. (c) Using semihigh-speed steel, all others are
high-speed steel. (d) Compound, soluble oil 10% and 1 lb heavy soap per 20 gal. Source: Ref 1
274 / Fabrication and Finishing

Table 12 Band saw teeth and speeds

Stock diameter of thickness, mm (in.)
1.6–6.4 (1/16 1/4) 6.4–25 (1/4 1) 25 (1)
Teeth Velocity Teeth Velocity Teeth Velocity
Machinability
rating of alloys per cm per in. m/s ft/min per cm per in. m/s ft/min per cm per in. m/s ft/min

70–100 7 18 2.5–5.1 500–1000 4 10 1.8–2.3 350–450 1.5 4 1.3–1.8 250–350

30–60 7 18 1.3–1.8 250–350 4 10 1.2–1.3 230–250 1.5 4 1.0–1.2 200–230
20 (except copper) 7 18 1.3–1.5 250–350 4 10 1.0–1.3 200–250 1.5 4 0.8–1.0 150–200
Copper 7 18 4.1–7.6 800–1500 4 10 3.0–5.1 600–1000 1.5 4 1.5–3.0 300–600

Source: Ref 3

data in Table 12 will aid considerably in selecting mended for all types of grinding except for can be found in Machining, Volume 16 of
a good combination of saw tooth and linear speed. surface grinding softer alloys. For these con- ASM Handbook.
For power hacksaws, a good rule in select- ditions, silicon carbide wheels are preferred. Electrical Discharge Machining. In the
ing saw tooth pitch is to use fewer teeth for In all cases, vitrified bond wheels of medium EDM process, metal is removed by rapid spark
thick sections to provide for better chip clear- grade (J to N) are recommended. Emulsions discharges between an electrode and a conduc-
ance, and more teeth for thinner sections. Data of soluble oil and water are satisfactory grind- tive workpiece separated by a 0.013 to 0.9 mm
for power hacksawing are listed in Table 13. ing fluids. (0.0005–0.035 in.) gap filled with a dielectric
fluid. The workpiece is melted, vaporized in
Grinding (Ref 4) part, and expelled from the gap. Figure 18 shows
Nontraditional Machining Methods a typical EDM setup.
The grinding of copper alloys is not com-
Electrical discharge machining is often used to
mon, but in some applications grinding is the Nontraditional machining methods com-
produce beryllium-copper mold components for
best means of obtaining accuracy and finish. monly carried out on copper and copper
injection molding of plastics. The effectiveness of
Sometimes, when finish grinding must supple- alloys include electrical discharge machining
EDM is not dependent on the strength or hardness
ment machining, one grinding operation can (EDM), electrochemical machining (ECM),
of the workpiece, and the beryllium copper can be
be used to replace both operations. and photochemical machining (PCM). Each
machined in the age-hardened condition without
Speeds, feeds, and wheels are given in of these processes are briefly described
affecting strength and with no need for further
Table 14. Aluminum oxide wheels are recom- subsequently. More detailed information
heat treatment. The EDM process is also used to
drill small, burr-free holes in miniature compo-
nents and for making prototype quantities of con-
tacts for aerospace and electronic components.
Electrochemical machining is the controlled
removal of metal by anodic dissolution in an
electrolytic cell in which the workpiece is the
anode and the tool is the cathode. The electrolyte
is pumped through the cutting gap between the
tool and the workpiece, while direct current is
passed through the cell at a low voltage, to dis-
solve metal from the workpiece. Figure 19
shows a typical setup for ECM.
The ECM process is used to machine oddly
shaped, small deep holes in copper and copper
alloys that would be difficult, if not impossible,
to make by mechanical machining.
Electrochemical machining is used for opera-
tions as widely different as milling, drilling,
deburring, etching, and marking.
Photochemical machining, also known as
chemical blanking, is a metal-etching process
that uses a photoresist (photosensitive masking)
to define the locations where the metal will be
etched (removed) (Ref 7). The PCM process is
Fig. 17 Solid and inserted tooth shapes for circular saws used for copper and copper alloys. Source: Ref 1
used to produce intricate and close-tolerance
patterns in a variety of flat parts (including foil)
with a thickness range of 0.01 to 1.6 mm
Table 13 Power hacksaw teeth and speeds (0.005–0.062 in.).
Stock diameter or thickness, mm (in.) Copper and copper alloys are among the most
6.35–25.4 (1/4 1) 25.4 (1) etchable metals used in photochemical machin-
Teeth Teeth
ing. Electrolytic copper, oxygen-free copper,
Workpiece material per cm per in.
Strokes
per minute per cm per in.
Strokes
per minute
beryllium copper, brass, phosphor bronze, cop-
per nickel, and nickel silver flat products are
Free-cutting type I alloys 2.4–4 6–10 130–150 1.6–2.4 4–6 130–150
Short-chip type II alloys 2.4–4 6–10 90–120 1.6–2.4 4–6 90–120
readily processed using the PCM process.
Long-chip type III alloys 2.4–4 6–10 60–90 1.6–2.4 4–6 60–90 Products include contacts and terminals, lead
Source: Ref 1
frames, and copper foil/plastic printed circuit
board laminates.
 Machining / 275

Table 14 Conditions for the grinding of copper alloys

Surface grinding Cylindrical grinding Centerless grinding
Wheel classification Work speed, m/min (sfm) 30 (100) Regulating wheel
Workpiece 20–70 HRB C-46-K-V Infeed Angle 3˚
Workpiece 60–100 HRB A-46-K-V Rough, mm/pass (in./pass) 0.05 (0.002) Speed 30 rev/min
Wheel speed, m/min (sfm) 1680–1980 (5500–6500) Finish, mm/pass (in./pass) 0.01 (0.0005) max Internal grinding
Table speed, m/min (sfm) 15–30 (50–100) Traverse Wheel classification
Downfeed Rough 1/3 wheel width/work rev Workpiece 20–70 HRB A-46-J-V
Rough, mm/pass (in./pass) 0.075 (0.003) Finish 1/6 wheel width/work rev
Workpiece 60–100 HRB A-60-L-V
Finish, mm/pass (in./pass) 0.01 (0.0005) max Wheel speed, m/min (sfm) 1520–1980 (5000–6500)
Crossfeed 1/3 wheel width/pass Centerless grinding
Work speed, m/min (sfm) 30–60 (100–200)
Cylindrical grinding Grinding wheel classification A-60-L-V Infeed
Wheel speed, m/min (sfm) 1680–1980 (5500–6500) Rough, mm/pass (in./pass) 0.05 (0.002)
Wheel classification Work feed, mm/min (in./min) 125 (50) Finish, mm/pass (in./pass) 0.005 (0.0002)
Workpiece 2–70 HRB A-60-N-V Infeed Traverse
Workpiece 60–100 HRB A-46-L-V Rough, mm/pass (in./pass) 0.13 (0.005) Rough 1/3 wheel width/work rev
Wheel speed, m/min (sfm) 1680–1980 (5500–6500) Finish, mm/pass (in./pass) 0.04 (0.0015) max Finish 1/6 wheel width/work rev

Source: Metcut Research Associates Inc.

Fig. 18 Typical setup for electrical discharge machining. Negative (standard) polarity
is shown. Positive (reverse) polarity is also extensively used. Source: Ref 5 Fig. 19 Schematic of the electrochemical machining system. Source: Ref 6

REFERENCES 4. M.L.H. Wise, M.A. Staley, and M. Samandi, SELECTED REFERENCES

Machining of Copper and Copper Alloys,
1. Copper Rod Alloys For Machined Products, Machining, Vol 16, ASM Handbook, ASM • “Alloy Data Sheet: SeBiLOY, Low-Lead Red
Copper Development Association, 1996, International, 1989, p 805–819 Brass Casting Alloys C89510 and C89520,”
p 41–43, 85–93 5. J.E. Fuller, Electrical Discharge Machining, Document No. A1032-00, Copper
2. “Comparative Machinability of Brasses, Steels, Machining, Vol 16, ASM Handbook, ASM Development Association, 1995
and Aluminum Alloys: CDA’s Universal International, 1989, p 557–564 • “Machinability of Copper-Based Alloys,”
Machinability Index,” SAE Technical Paper 6. T.L. Lievestro, Electrochemical Machining, Project Report 384, International Copper
Series, Number 900365, SAE International, 1990 Machining, Vol 16, ASM Handbook, ASM Research Association, 1985
3. G. Joseph and K.J.A. Kundig, Copper: Its International, 1989, p 533–541 • “The Machining of High-Conductivity
Trade, Manufacture, Use, and Environmental 7. H. Friedman, Photochemical Machining, Copper,” Project Report 343A, inter-
Status, International Copper Association, Ltd. Machining, Vol 16, ASM Handbook, ASM national Copper Research Association,
and ASM International, 1999, p 259–271 International, 1989, p 587–593 1984