Copper Development Association
Cost-Effective Manufacturing
Machining Brass, Copper and its Alloys
Publication TN44, 1992
Cost-Effective Manufacturing
Machining Brass, Copper and its Alloys
Publication TN 44
October 1992 – Revised for inclusion on CD-Rom, May 1994
Members as at 1st January 1992
ASARCO Inc
Boliden MKM Ltd
Thomas Bolton Ltd
BP Minerals International Ltd
Brandeis Ltd
The British Non-Ferrous Metals Federation
Chile Copper Ltd
CIPEC
Falconbridge Ltd
Gecamines Commerciale
Highland Valley Copper
IMI plc
Inco Europe Ltd
Minpeco (UK) Ltd
Noranda Sales Corporation of Canada Ltd
Palabora Mining Co Ltd
Rtz Limited
Southern Peru Copper Corporation
Wednesbury Tube
Acknowledgements
The preparation of this publication has been financed by International Copper Association.
CDA is also glad to acknowledge useful comments on the draft text, particularly from Dr M Staley (BNFFulmer), Eur Ing Mr J Westlake (Boliden MKM Ltd), the late Mr P Wilkins (Delta Extrusion) and Dr M
Wise (University of Birmingham).
Copper Development Association
Copper Development Association is a non-trading organisation sponsored by the copper producers and
fabricators to encourage the use of copper and copper alloys and to promote their correct and efficient
application. Its services, which include the provision of technical advice and information, are available to
those interested in the utilisation of copper in all its aspects. The Association also provides a link between
research and user industries and maintains close contact with other copper development associations
throughout the world.
Website:
www.cda.org.uk
Email: helpline@copperdev.co.uk
Copyright:
All information in this document is the copyright of Copper Development Association
Disclaimer: Whilst this document has been prepared with care, Copper Development Association can give
no warranty regarding the contents and shall not be liable for any direct, indirect or consequential loss
arising out of its use
Contents
Contents........................................................................................................................................................1
Figures ...........................................................................................................................................................2
Tables – .........................................................................................................................................................2
Introduction .................................................................................................................................................4
Costings ........................................................................................................................................................5
Manufacturing Costs......................................................................................................................................5
Material Costs..............................................................................................................................................10
Starting stock types .................................................................................................................................10
Scrap Recovery............................................................................................................................................11
Illustrations - Cheaper than Steel, Stainless Steel and Aluminium .......................................................12
Illustrations – Wrought Preforms for Quick Machining .......................................................................14
Machinability Groups ...............................................................................................................................16
Group 1 - Original Machinability Rating 170 - 150% .................................................................................16
Group 2 - Original Machinability Rating 30 - 60% .....................................................................................16
Group 3 - Original Machinability Rating less than 30%..............................................................................16
Machining Operations...............................................................................................................................29
Tool Materials .............................................................................................................................................29
High speed steels.....................................................................................................................................29
Indexable insert carbide tools..................................................................................................................29
Brazed tip carbide cutting tools...............................................................................................................30
Carbide Tool Materials ...........................................................................................................................30
Diamond Tipped Tools ...........................................................................................................................31
Polycrystalline Diamond (PCD)..............................................................................................................31
Turning ........................................................................................................................................................31
Sand Castings ..........................................................................................................................................31
Wrought Materials ..................................................................................................................................31
Chipbreaker Tools...................................................................................................................................34
Cutoff tools..............................................................................................................................................36
Form tools ...............................................................................................................................................36
Drilling ........................................................................................................................................................37
Tapping........................................................................................................................................................38
Reaming.......................................................................................................................................................39
Milling .........................................................................................................................................................41
Materials Selection ....................................................................................................................................42
High speed machining brass ........................................................................................................................43
Rod for Free-machining purposes................................................................................................................43
Coppers and Copper Alloys.........................................................................................................................44
Coppers........................................................................................................................................................44
Brasses.........................................................................................................................................................44
Nickel-Silvers ..............................................................................................................................................45
Bronzes........................................................................................................................................................45
Copper-nickel alloys and the Aluminium Bronzes ......................................................................................45
Dimensional tolerances and straightness .....................................................................................................46
Dimensions ..................................................................................................................................................46
Machining preforms made by hot stamping or forging................................................................................48
Materials for Castings for Subsequent Machining.......................................................................................51
Material Availability....................................................................................................................................51
Group 1 alloys .........................................................................................................................................51
Group 2 alloys .........................................................................................................................................51
Group 3 alloys .........................................................................................................................................51
1
Illustrations - Cast Preforms .................................................................................................................... 53
Illustrations – High Precision................................................................................................................... 54
Illustrations – Repetition Jobs.................................................................................................................. 56
Illustrations – Short Runs......................................................................................................................... 57
Illustrations – Machining HC Coppers ................................................................................................... 59
Machinability Testing Methods ............................................................................................................... 60
Cutting Fluids for Copper Alloys............................................................................................................. 64
Functions of cutting fluids........................................................................................................................... 64
Selection and application of cutting fluids .................................................................................................. 64
Type of work material ................................................................................................................................. 65
Effect of Tool Material................................................................................................................................ 65
Type of machining operation....................................................................................................................... 65
Type of cutting fluid.................................................................................................................................... 65
Lubricant Manufacturers’ Recommendations.............................................................................................. 67
Addresses of Lubricant Manufacturers........................................................................................................ 78
References .................................................................................................................................................. 79
Figures
Figure 1 – Estimation of economic cutting speed (ignoring fixed costs)....................................................... 6
Figure 2 - Universal machinability ratings for a variety of materials (ref. 1), giving a guide to comparative
machining costs. ............................................................................................................................................ 6
Figure 3 – Chip forming classification (ref 13) ........................................................................................... 28
Figure 4 - Carbide tipped lathe turning tools............................................................................................... 32
Figure 5 – Diagram showing land width and chip breaker tool action ........................................................ 34
Figure 6 – SIR diagram for determining chip breaker parameters............................................................... 35
Figure 7 – Circular and straight cutoff tools................................................................................................ 36
Figure 8 – Drill point and clearance angles ................................................................................................. 38
Figure 9 – Spiral pointed tap ....................................................................................................................... 39
Figure 10 - Typical stub auto reamer........................................................................................................... 40
Figure 11- Chasers for die heads and collapsible taps................................................................................. 41
Figure 12- Milling cutter rakes and clearances............................................................................................ 42
Figure 13 - Geometry of component and schematic diagram of machining operations in tests conducted by
Davies (ref. 4).............................................................................................................................................. 61
Tables –
Table 1 – Comparison of costs of parts made in brass and steel (ref 2)(a) ......................................................... 7
Table 2- Relative Machinability Ratings of Various Metals (after (ref. 22)) ................................................ 9
Table 3 - Wrought coppers and copper alloys – availability, properties and machinability........................ 17
Table 4 – Cast coppers and copper alloys – applications, properties and machinability............................. 24
Table 5 - DKI scheme for classifying machinability of coppers and copper alloys..................................... 28
Table 6 – Tool Geometry Recommendations (ref. 14)................................................................................ 33
Table 7 – Speeds and feeds for turning ....................................................................................................... 33
Table 8 – Speeds and feeds for drilling ....................................................................................................... 37
Table 9 – Tapping speeds............................................................................................................................ 39
Table 10 - Reaming speeds and feeds ......................................................................................................... 40
Table 11 – Speeds for thread chasing.......................................................................................................... 40
Table 12 – Speeds for milling ..................................................................................................................... 42
Table 13 – Materials commonly available as rods for free-machining purposes......................................... 46
Table 14 – Materials for hot stampings and forgings .................................................................................. 49
Table 15 – Lubricant manufacturers’ recommendations ............................................................................. 68
2
This publication is aimed at:
Those wanting a full introduction to the factors affecting machining as a production
technique:
Start at Introduction and work onwards.
Those requiring guidance on materials selection where good machinability is one of the
important properties:
See Introduction, Machinability Groups and Materials Selection first
Those who know what material is to be machined and require basic information and
guidance:
See Introduction, Machinability Groups, Machining Operations and Cutting Fluids for Copper
Alloys first
Those requiring an update on relevant recent technical developments:
See the main list of contents for subjects of interest.
Common abbreviations for alloying elements
Ag
Silver
Ni
Nickel
Al
Aluminium
P
Phosphorus
As
Arsenic
Pb
Lead
Be
Beryllium
Si
Silicon
Cr
Chromium
Sn
Tin
Co
Cobalt
Te
Tellurium
Cu
Copper
Zn
Zinc
Fe
Iron
Zr
Zirconium
Mn
Manganese
"It is the aim of this publication to promote amongst engineers generally a wider knowledge
and appreciation of the machining qualities of copper alloys and also serve as a book of
reference as to the methods whereby these qualities may be exploited to the best advantage." W.
B. S.
From the forward to the book: 'The Machining of Copper and its Alloys', Copper Development
Association Publication No 34, 1939.
3
Introduction
As one of the most important of manufacturing production processes, machining operations can
contribute significantly to profitability. Using the most suitable materials and the best
techniques can result in economies in production costs that keep products ahead of competition.
Examples in this publication show that components can be made more cheaply in materials such
as free-machining brass than from other materials of lower first cost.
As part of the process of the manufacture of components, machining is frequently a vital, costeffective step. It has many advantages:
Versatility - resetting a machine can be much easier than redesigning complex tooling for
mouldings
Good Surface Finish
Accuracy - machining tolerances are far closer than those obtained by most other production
processes
Good Screw threads
Best materials - choice is not limited since all metals can be machined
Low Cost - for many products and production runs, well planned machining operations can be
the most cost-effective production method.
All coppers and copper alloys can be machined accurately, cheaply and to a good standard of
tolerances and surface finish. There are materials that are specially made with excellent
machinability as a primary attribute; the best of the free machining brasses set the standard by
which all other materials are judged. Other alloys are made with a variety of combinations of
properties such as strength, corrosion resistance and cold formability as the primary concerns.
These may be less easily machined but techniques are readily available and machining may well
be easier and cheaper than for many other types of material.
For many years, the International Copper Association (ICA), previously known as International
Copper Research Association (INCRA), has sponsored significant programmes in connection
with the development of free-machining alloys and improvements in techniques of machining
existing coppers. Reference is made to the importance of the results of this work in this
publication.
As part of the harmonisation processes continuing throughout Europe, there will shortly be
published a series of new standards to be adopted by all European national standards
organisations without modification. These will supersede all previous European national
standards. The materials included are likely to be similar to those already in use but with new
designations, a new numbering system and with attributes such as composition and properties
that reflect current production requirements. The materials described in this publication are
those most likely to be included in the European standards.
4
Costings
Correct costing of a product is vitally important. Ignoring overheads,
component costs = initial material costs + production costs
Component costs should also include the consequential costs of failures before and after
despatch, that is, the cost of ensuring fitness for purpose.
Consideration needs to be given to the effect of variations in material costs in reducing
production costs. It is usually a false economy to aim only at lowest first cost for material.
Each organisation will have a costing system suited to requirements; the factors that will be
considered include all those contributing to lowest total costs of components that are fit for the
end-use purposes.
Product costs include not only raw material costs but also the costs of converting the material to
the final shape and size, provision of surface protection and/or decoration together with possible
service costs throughout the life of the product. Energy costs of the production process and costs
of tooling and special equipment that may be needed are other considerations.
Copper and its alloys have been recycled effectively for thousands of years. Recycling of
both process scrap and the product itself at the end of its working life are therefore also wellestablished relevant factors.
This publication is dedicated to aspects of cost-effective machining. Other CDA publications
cover the many advantages that coppers and the copper alloys have over alternative materials
such as high strength, ductility, toughness and conductivity at ambient, low and elevated
temperatures, excellent corrosion resistance and no problems with ageing or degradation by
daylight.
These benefits can make coppers and copper alloys the most cost-effective choice when all
production considerations are evaluated.
Manufacturing Costs
In designing a component, consideration needs to be given to keeping production costs as low as
possible, consistent with maintenance of quality. This means keeping machine output high by
the use of easily finished feedstock that is both as near final size and as easy to machine as
possible. Selection of the best materials and machining techniques is essential.
The recommendations of this publication will be found a useful guide. Experience gained during
production operations will allow the introduction of relevant improvements.
In estimating ways of minimising the cost of manufacturing a component, one of the factors to
be considered is the cutting speed. An increase in cutting speed normally has two main effects,
the metal removal rate is increased and the tool life is decreased. The first saves money but
downtime for tool changing increases costs and a best compromise of least costs has to be
evaluated to obtain the most economic cutting speed, see Fig 1.
5
Figure 1 – Estimation of economic cutting speed (ignoring fixed costs)
Selecting a material stock that is suitable for high-speed machining can allow an increase in
machining speeds without increasing tooling costs.
This will have a very beneficial effect on productivity.
Figure 2 - Universal machinability ratings for a variety of materials (ref. 1), giving a guide to
comparative machining costs.
6
Table 1 – Comparison of costs of parts made in brass and steel (ref 2)(a)
Component
Fitting
Manifold
adaptor
Air brake
Hose fitting
Actuating
sleeve
Pneumatic
hose fitting
Knob insert
(knurled)
Underwater
pump
assembly
Automotive
Automotive
Pneumatic
power
Aircraft
Garden
equipment
Teflon
coated
Better
quality
cheaper
Safety-related
Deep hole
Deep hole
Productivity
savings
Part weight (g)
49
33
41
36
26
5.4
Brass (b)
premium (%)
23
30
36
17
42
32
Cycle time –
Brass (sec)
4.5
3.2
5.6
4.75
3.7
3.75
Cycle time –
Steel (sec)
8.0
5.9
9.1
8.4
8.3
5.5
Productivity
gain using brass
(%)
102
110
86
102
157
68
Cost saving
using brass
(£1/1,000)
3.92
0.58
33.98 (c)
40.60 (d)
25.08 (e)
2.62
body
Application
Special
Features
Notes:
(a) Comparisons are between CuZn36Pb3 (CZ124) free-machining brass and leaded free-machining steel 12L14. Comparisons are
based on multi-spindle auto production.
(b) Brass material cost premium includes scrap allowance.
(c) Brass v plated steel. For bare steel the saving is £26.26 per 1,000 parts
(d) Brass v plated steel. For bare steel the saving is £33.58 per 1,000 parts
(e) Brass v plated steel. For bare steel the saving is £20.09 per 1,000 parts
(Courtesy CDA Inc, USA)
7
Fig 2 shows machinability ratings for a selection of materials such as high-speed machining
brass, a leaded ductile brass, naval brass, a wrought aluminium alloy and a leaded freemachining steel. These results are comparable since they were obtained under identical testing
conditions to ASTM E 618 and are derived from the conditions needed to attain an eight hour
tool life using form tools and drills in an automatic lathe using 19mm feedstock to produce a
total of 80,000 components (ref. 1).
As Table 1 shows, the economic benefit to be obtained (ref. 2) by specifying free-machining
brass can mean that its use can frequently be justified on production costs alone, before
consideration of other properties such as strength, conductivity and corrosion resistance.
Table 2 gives some comparisons with other materials showing the better machinability of brass
and other copper alloys, when compared with other materials that might be considered for
component manufacture. Particularly noticeable is the comparatively good machinability of the
aluminium bronzes when compared with materials used in similar corrosive environments such
as stainless steel and Monel.
8
Table 2- Relative Machinability Ratings of Various Metals (after (ref. 22))
Machinability ratings according to Carboloy Systems Div. where steel En1a = 1.00.
The higher the rating, the better the machinability.
Material
Description
BS Designation
US
Designation
Hardness
HB
Machinability
Rating (steel)
Old
New
Free-cutting mild
steel
En1a
220M07
B1112
160
1.00
Plain low carbon
steel
En3
070M26
C1025
143
0.65
Plain medium
carbon steel
En8
080A40
C1040
205
0.60
High strength low
alloy steel 1.5%
NiCrMo
En24
817M40
A4340
210
0.50
High strength low
alloy stee l2.5%
NiCrMo
En25
826M31
6407
180
0.50
1% carbon, 1% Cr
ballbearing steel
En31
535A99
E52100
206
0.30
Low carbon case
hardening steel
En32
080M15
C1015
131
0.60
18/8 stainless steel
En58j
316
316
195
0.35
K-Monel
K500
240
0.35
Titanium alloy
A-70
188
0.27
Titanium alloy
C-130
255
0.18
Aluminium alloy
AA2017
2017-T
95
1.40
Free-cutting
aluminium alloy
AA2011
2011
95
2.00
Aluminium bronze
CA104
CuAl10Ni5Fe4
C63000
200
0.60
Aluminium silicon
bronze
CA107
CuAl6Si2Fe
C64400
180
1.80
Copper-chromium
CC101
CuCr1
C18200
140
0.60
Copper-nickel
CN102
CuNi10FeMn
C70600
90
0.60
Copper
C101
Cu-ETP
C11000
50
0.60
Free-machining
copper
C109
CuS
C14700
50
2.40
Forging brass
CZ122
CuZn40Pb2
C35300
70
2.70
Free-cutting brass
CZ121
CuZn39Pb3
C36000
70
3.0
9
Material Costs
The initial cost of material is only part of its contribution to total product cost. Careful
optimization of feedstock can reduce significantly the subsequent production costs by
minimising the amount of finish machining that is required. The machinability of the material
should be as good as possible, while still being compatible with other property requirements, in
order to maximise production rates. Selection of optimum materials is discussed in the
following sections.
The size and shape of the feedstock can also be tailored to suit; the closer it is to final size,
the lower the costs of finish machining.
Having considered the size of the production run and many other economic and technical
considerations, the most economic starting stock for finish machining can be selected from
many types of wrought and cast forms. Dependent on component design and the amount of
metal to be removed, many of these can be classified as 'near net shape' costing little to finish.
Starting stock types
Stock supplied in long lengths - easily fed in to a machine; may be dimensionally correct as
supplied in two dimensions only:
•
Extruded round rod, supplied in straight lengths with or without chamfered ends
that facilitate entry in to machine tools.
•
Extruded rectangle, hexagon or other profile nearer to net shape. The extra cost
over round rod offset by product cost savings over a long run.
•
Extruded hollow round, hexagon or other profile.
•
Extruded and drawn stock round or shaped rod or section supplied in straight
lengths or wire supplied in coil for semi-continuous feedstock. Drawing improves
properties and gives closer dimensional tolerances.
•
Continuously cast round or profile supplied in straight lengths solid or hollow.
Three-dimensional Preforms
•
Simple hot stampings made in low-cost dies - a wrought material of good strength and
relatively low cost.
•
More complex hot stampings made nearer to final shape requirements. Secondary
dies allow the inclusion of hollows.
•
Sandcastings - for relatively short runs of complex shapes, ideal for valves and other
pipe fittings, pumps and heavy electrical components.
•
Diecastings, gravity or pressure type - for longer runs of complex components made
to close tolerances and needing machining only for close-tolerance faces or holes.
10
Flat Stock
•
Rolled plate, sheet or strip - for components made flat or bent, pressed or deep drawn
to shape in short or long runs.
•
Further details of these production methods and the considerations that apply are
given in a CDA Datadisk (ref. 21).
Scrap Recovery
Where significant quantities of scrap are generated the effect of resale value in reducing product
costings can be significant. Copper and copper alloys have been recycled as part of production
economics for many centuries; however, techniques are still being improved. It is well worth the
effort to ensure that scrap is kept segregated by alloy and free from contamination. It is also
frequently worth recovering lubricant for re-use, clean swarf commands a better price since
contaminants have an adverse effect on the remelting environment.
When significant economic quantity orders are being negotiated with manufacturers, the value
of agreed returns such as swarf, offcuts and rod ends can make a useful contribution to profit.
Smaller users can also gain by careful segregation and disposal of scrap, especially if benefits
are built in to employee incentive schemes.
11
Illustrations - Cheaper than Steel, Stainless Steel and Aluminium
Screw Manufacture
(Delta EMS Ltd)
Bar feed automatic capstan lathes are used to produce millions of screws. Continuous feed from coiled rod
ensures maximum production rates. It is important to ensure quality control on the coil material so that the
machining parameters are kept constant.
The real cost of producing a component is the sum of the cost of the material and the cost of work
performed on it. It is obviously false economy to use material of the cheapest first cost if subsequent extra
production costs outweigh the savings.
Machinability Demonstration
The dramatic differences in machinability of brass and steel were underlined by this demonstration.
"Kebabs" made up of alternate sections of brass and steel were turned using a carbide tipped finishing tool.
The picture shows the marked differences in the swarf types.
12
Valve Chest
(Meco International)
This component is a good example of the cost savings which can be achieved by radical re-assessment of
the design. The part is machined from shaped extruded brass bar using programmed robotically controlled
tooling. The use of the extruded preform minimises waste material.
Part of a motor casing
Cable glands and fire extinguisher heads in
aluminium and brass
(Hayward Tyler Fluid Dynamics Ltd)
(Hawke Components Ltd)
This picture shows two examples of components
which can be manufactured in either aluminium or
brass. The cable glands are cheaper in brass
because it is easier to machine and less labour
intensive. Free machining aluminium cannot be
used because it does not have adequate corrosion
resistance. The fire extinguisher head is made out of
brass because aluminium tends to gall when
screwed into a steel cylinder.
This is part of a motor for a fire pump to operate
undersea for fire protection of North Sea oil rigs.
The casting is in aluminium bronze to BS1400
AB2. This material is used in preference to stainless
steel because of the 50% saving in machining costs.
With a machining operation of this complexity this
saving represents considerable sums of money. The
accurate external work is completed first, and then
the internal grooves to locate the stator and end
plates are machined. The set-up time can be as long
as 16 hours and the machining takes 4 days with a
further 5 days taken up with milling and tapping.
13
Illustrations – Wrought Preforms for Quick Machining
Chamfered brass rod ready for despatch
(Boliden MKM Ltd)
Chamfered ends facilitate easy entry of bars into automatic lathes.
Extruded Hexagonal Bar
(Delta Extruded Metals Co Ltd)
Components made from this high speed machining rod are shown along side the bar stock emphasising the
efficient use of material.
14
Tube plate
T Piece and Bushing
For small batches, this tube plate is machined from brass
plate 8mm thick. For larger batch production, savings can
be made by starting with a diecast preform which
eliminates all but a final finish machine.
(Delta EMS Ltd)
Near-net-shape hot stampings provide cost-effective preforms
for these parts. Machining is then only required on mating
faces and for threading.
A selection of extruded profiles
Fittings for the pneumatics industry
Complex profiles can be extruded to order. In many cases
the die costs are quickly repaid by savings in machining
time and the reduction in material wastage.
(Norgren Martonair Ltd)
This push-in tube is shown at various stages of its
manufacture. Hot stamping as it comes out of the die; after
cropping and acid dipping; machined; and finally, bright
nickel plated. The maching takes place in one operation on
automatic CNC machines.
Union Nut
Shaped Hollows
(Delta EMS Ltd)
Standard shapes of hollow bar are available from stock and,
though slightly more expensive than solid bar, will often prove
to be a more cost-effective choice for the manufacture of
hollow components.
These fittings could easily be produced from solid rod,
hollow rod or from hot stampings. For reasonably long
production runs hot stampings are the most cost-effective
choice. Machining is only required to thread the finished
nuts.
Complex shaped hollows can be produced to special order.
15
Machinability Groups
For centuries, copper and copper alloys have been used to make a very wide variety of products
that depend for their usefulness on combinations of such properties as strength, ductility,
hardness, conductivity and corrosion resistance. They have an appearance that is functional,
decorative and an accepted indication of good quality and fitness for purpose.
Compositions and available forms have been developed to meet nearly every need of the
engineering designer and this has resulted in a very wide range of materials being available. The
needs of production engineers have also been met by modifications that enable many of the
materials to be fabricated easily and cheaply. Some are less easy to machine than others because
to make them so would prejudice other properties.
In the new European standards there are likely to be about 40 compositions standardised for cast
coppers and copper alloys and about 140 for wrought materials. These standards will shortly be
adopted without modification by all European countries, replacing existing national standards
such as the present BS 2870 to 2875 series for wrought semi-manufactured coppers and copper
alloys and BS1400 for cast coppers and copper alloys. Broadly, they include most of the first
preference materials from all existing European national standards. Other similar materials are
included in ASTM specifications. Most of these are available in differing forms and tempers
that also affect machinability.
In machining, the cutting action involves initially shearing the cut metal (as swarf or chips) from
the machining stock and then removing the swarf from the cutting tool in a way that allows
further swarf to follow freely. Both of these actions are controlled by a wide variety of factors,
of which the metal composition and structure is one. Others include, for example, tool geometry
and cutting speeds and feeds.
Because of the numbers and interaction of these variables, machinability ratings are, therefore,
for initial guidance only, and should be developed further in the light of experience.
For machining purposes, coppers and copper alloys can be roughly divided in to three
categories:
Group 1 - Original Machinability Rating 170 - 150%
Materials specifically made to be freely machinable. These have alloying additions that
encourage the formation of short-chipping swarf that clears easily from the toolface. They
enable components to be produced very quickly, accurately and cheaply. The group includes the
free-machining brasses, coppers and bronzes.
Group 2 - Original Machinability Rating 30 - 60%
Materials with good machinability but with first priority given to other properties. Typical materials in this
group are the unleaded brasses.
Group 3 - Original Machinability Rating less than 30%
Materials that are not as easy to machine as the alloys in groups 1 and 2 because they are longer
chipping. They may generate higher temperatures and stresses on cutting tools because of their
mechanical properties. They can be successfully handled using techniques that may be similar in
some respects to those needed for many ferrous materials and usually at lower speeds than those
used for groups 1 and 2.
16
Table 3 - Wrought coppers and copper alloys – availability, properties and machinability
17
18
19
20
21
22
23
Table 4 – Cast coppers and copper alloys – applications, properties and machinability
24
25
26
A summary of the coppers and copper alloys commonly available in Europe is included in Table
3 and Table 4 together with the range of properties, remarks regarding usage and guidance on
machining techniques.
The 'Machinability Group' is the broad classification previously described giving a good
general idea of machining characteristics.
The 'Percentage Machinability Rating' figures were originally derived after a consideration of
a number of the factors involved in machining, namely: chip size, surface finish and power
requirement. The original free machining brass (CZ121) containing a nominal 3 per cent lead
was given a rating of 100 and other alloys divided into the three groups shown above.
The machining (turning) parameters of feed, speed and depth of cut as well as tool rake and
clearance angles were linked to these groupings for tools made of carbon- and high speed steels
and with carbide tips. The ratings are arbitrary, applying mainly to simple turning processes but
having some significance for other operations such as form turning, drilling, thread turning and
milling. In view of the difficulties in applying the original machinability ratings to all types of
operations, the use of the Groups is a better general guide, together with remarks pertinent to
each material.
Materials, tool geometry, cutting rates, lubricants and other factors all affect machinability and
are discussed in other sections. The indicated speeds and feeds, together with the rake and
clearance angles may be taken as starting points which can be modified subsequently to
suit such variables as machine tool characteristics, material composition, grain structure
and temper together with depth of cut, cutting fluid and the requirements of the ultimate
application.
The use of special techniques can make machining of some materials not normally rated as 'freemachining' comparatively easy. An example of this is the use of chipbreaker tool geometry for
machining high conductivity copper. As described later, this results in the swarf being readily
cleared from the toolface, giving better surface finish and much higher production rates.
Also included in the tables are data extracted from a DKI publication (ref 14). This includes
consideration of the effect of material condition, characterised by tensile strength and hardness,
on machining characteristics. For the wrought alloys, this causes some modification of their
machinability groups, as defined in Table 3, according to structure, swarf type, typical tool wear
and formability.
In addition to these criteria the chip characteristics have others such as modulus of elasticity,
specific heat, thermal conductivity, material texture and others so that within a given chip
grouping other specific characteristics can be included.
Main group I
Comprises lead, tellurium or sulphur, alloyed copper base materials with homogeneous or
heterogeneous structure which are easily machinable.
Main group II
Contains moderately or well machinable (mostly lead free) copper base materials of higher
mechanical strength and better cold working characteristics than the materials comprising group
1 metals with heterogeneous structure which, because of their better plasticity, produce longer
swarf.
27
Main group III
This includes two types of copper-based materials that are not so easy to machine. Type 'a', with
their homogeneous structure and excellent cold working characteristics produce strong swarf
and long, tough swarf ribbons. Type 'b' contains heterogeneous materials such as high strength
copper-aluminium alloys (aluminium bronzes) and the low alloyed copper-based materials in the
hardened condition.
Table 5 - DKI scheme for classifying machinability of coppers and copper alloys
Main Group I
Main Group II
Main Group III
Homo/heterogeneous
with chip breaking
particles
(Pb, S, Te)
Heterogeneous
(coarse dispersed
phases) without
Pb particles
a. Homogeneous
b. Heterogeneous
(fine dispersed
phase)
Short (brittle chip)
Medium (helical chip)
Long and tough
(strip, tangle and helix)
Low
Medium
High
Cold forming of wrought
material
Generally poor
Generally good
a. Very good
b. Inferior
Hot forming of wrought
material
Generally good
Moderate
a. Moderate
b. Good
Characteristic
Structure
Swarf type
Tool wear (relative)
The types of swarf categorised are subdivided in to other categories as shown in Fig 3.
Figure 3 – Chip forming classification (ref 13)
28
Machining Operations
Tool Materials
The most economic tool material can be chosen after consideration of factors such as run size,
tolerance requirements, downtime and toolsetting costs in addition to the actual cost of the
cutting tool.
There are five main types of cutting tools in common usage for copper based materials:
•
High Speed Steel (HSS)
•
Indexable Carbide Inserts
•
Carbide Brazed Tips
•
Diamond (single crystal)
•
Polycrystalline Diamond (PCD)
Ceramic and cermet tools are not commonly used for machining copper-based materials.
High speed steels
High speed steels are still used for many operations, especially for short runs where special
shapes and forms are necessary. They are relatively cheap and easy to regrind. Cutting speeds
are moderate but tool life is generally good with most brasses, coppers and copper alloys due to
the comparatively low temperatures generated during machining.
High speed steels differ from other steels by having a high content of stable carbides (about
27%), giving a good wear resistance and hot hardness. They are normally made by conventional
melting and working techniques; the various grades have different contents of alloying elements
such as cobalt and vanadium, and carbide structures that are dependent on the manufacturing
process. Sintered or hot isostatically pressed materials can show improved wear properties due
to the addition of higher contents of vanadium and other alloying elements not possible with
conventional manufacturing techniques.
Indexable insert carbide tools
Indexable insert carbide tools are now the most popular tool materials, a wide variety of grades
and geometries being available. Tool setting is very quick and production runs of over 120,000
cuts per edge are common. Tools are more frequently changed after accidental damage than
because of wear. The inserts are available in standard packages for operations such as turning,
boring and milling and are easily used on CNC machine tools.
The inserts are made by sintering a mixture of tungsten carbide and cobalt powders pressed to
the required shape. High cutting speeds and substantial metal removal rates are normal and a
copious supply of coolant should be directed at the component. The cutting speed should be
high enough to raise the temperature at the tool cutting edge sufficiently to prevent a built-up
edge forming since carbide tools are more sensitive to stress fluctuations and impact damage
than HSS tools. The upper cutting speed limit may be limited by any of several factors:
•
Component clamping and rigidity
•
Power available at the spindle
•
Heat generation, particularly with alloys of group 3.
29
•
Type of swarf and efficiency of its removal
•
Noise limitations
•
Safety considerations
If the speed is too low build-up occurs which can result in rapid attrition and hence wear of the
cutting edge.
Coated tips using wear resistant coatings such as titanium nitride should not be used except
when turning aluminium bronzes and do not offer much advantage in the machining of other
copper-based alloys compared with uncoated tools (ref 15). Since copper alloys are not
chemically aggressive to normal tool materials, the advantage is not so great as when some other
materials are machined.
Brazed tip carbide cutting tools
Brazed tip carbide cutting tools continue to retain their role in tooling programmes because of
the ease with which they can be adapted to particular requirements that may mean modified
radii, rake angle or special chipbreaker geometries. This type of cutter is often used when brass
or gunmetal is to be cut using combination multi-cutter gangs on a common spindle. This
necessitates the manufacture of fairly complex toolholders but the extra cost is offset by long
life, high machining rates and the advantage to productivity of multiple machining in one pass.
The speeds and feeds used are similar to those for indexable carbide tipped tools.
For special materials such as sintered copper-based components, carbide tips are useful for
reamers.
Carbide Tool Materials
Carbide Tool Materials are classified according to ISO 513 in terms of their suitability for three
main categories of application:
•
P for use with long-chipping materials
•
K for short chipping materials
•
M for intermediate grades
Group K materials are typically plain tungsten carbide and cobalt grades but some contain small
additions of tantalum carbide and titanium carbide. Groups M and P contain more titanium
carbide and tantalum to impart more wear resistance for the machining of steels, which is of
little significant benefit for the machining of most coppers and copper alloys.
Materials with a larger carbide grain size and higher cobalt content have a good toughness but
lower hardness, while smaller grain sizes and cobalt contents give better wear resistance but
lower toughness. Each group is therefore available in a number of grades with increasing
numerical values giving greater toughness but lower wear resistance. This means that increasing
the grade number (e.g. K40) permits an increased feed rate, decreasing it (e.g. K10) permits a
faster cutting rate.
For most free-machining brasses, coppers and copper alloys, K10 is generally recommended
with K20 used for interrupted cuts or milling. For more difficult jobs, K40 or M40 are
sometimes recommended while P01 or P05 can be used for high-speed finishing cuts.
30
Diamond Tipped Tools
Diamond tipped tools are not needed for most machining operations on coppers, but they have
been used for many years for special purposes, especially where fine finishes are required.
Typically, good quality commutators are finished with diamond tipped tools in order to
minimise brush wear in service. Copper components for special electronic purposes also benefit
from this type of finish. Naturally, care must be taken not to shatter the diamond. High
machining speeds and small cuts are normal, and frequently no lubricant is used.
Polycrystalline Diamond (PCD)
Polycrystalline Diamond (PCD) tipped tools can give extremely good tool life, possibly up to
five hundred times that of carbide. Machine down-time can therefore be reduced to an absolute
minimum. The very low wear rate can be used with advantage when extremely tight tolerances
on dimensions and surface finish have to be maintained over long production runs. Great care
must of course be taken not to crash the machine tools or the extra life advantage is lost.
Turning
The variables of speed, feed and depth of cut present almost unlimited combinations for
attaining economic machining rates. This is just as true for copper and the copper alloys as it is
for other engineering materials. For brasses and most other copper alloys, it is generally good
practice to use the highest practical cutting speed, a relatively light feed, and a moderate depth
of cut.
Sand Castings
Sand castings provide a particular exception to this rule. Most sand castings retain an extremely
hard and abrasive surface scale even after sand blasting, pickling, or tumbling. This hard surface
needs to be removed with one cut if possible, by using a low turning speed and a relatively
coarse feed in order to keep a reasonable tool life. After the scale has been removed, higher
speeds and lighter feeds can be used to advantage. If carbide tools are used for machining sand
castings there is less need for speed to be reduced for the initial heavy cut.
Wrought Materials
Wrought materials and cleaned castings can be machined using, as a guide, the basic
recommendations in Figure 4, table 6 and table 7. The indicated speeds, feeds, rakes and
clearances for cutting tools can be taken as starting points which can be modified to suit such
variables as composition, grain structure, temper, depth of cut, cutting fluid and the ultimate
application.
Speeds are quoted in surface metres per minute (sm/m) from which revolutions per minute
(rpm) can be calculated using the radius or diameter of the job.
31
Figure 4 - Carbide tipped lathe turning tools
Note:
Rake angles are based on the tool shank being set parallel with the centre line of the work and with the tool
point on centre. Placing the tool point above or below centre will change the effective rake angles
appreciable, particularly on work of small diameter. On a set-up where the tool holder is not parallel with
the centre line, the rake angles should be ground so that when the tool is mounted, they are in correct
relation.
The less ductile copper materials need little or no rake, while the more ductile alloys usually
benefit from a comparatively steep rake to prevent the formation of a collar by deformation
ahead of the cutting edge, but high rake angles result in the formation of continuous chips. The
moderate rake angles suggested for use on the alloys in Group 1 reduce the tendency of the tool
to hog into the work. More pronounced rakes are used for alloys in Group 2 and 3 to provide a
free chip flow. In fact, the side rake angles used for machining the alloys in Group 3 (the least
machinable) somewhat exceed those generally used for machining steel.
The rakes and clearances given in Figure 4 do not take into consideration tool shape, nose
radius, or front cutting edge angles for roughing or finishing cuts, which vary considerably and
depend on the particular job. In all cases the tool shank is assumed to be set parallel with the
centre line of the work and the tool point on the centre. Clearances should be only sufficient to
provide a free cutting action. On roughing cuts with carbon steel or high speed steel turning
tools, a nose radius of 0.8mm with up to 5° end cutting edge angle should prove satisfactory.
Too large a nose radius or too small an end cutting edge angle is often the cause of chatter. For
light finishing cuts, using a moderate speed and coarse feed, end cutting edge angles may be
smaller.
Table 6 shows more detailed recommendations from the DKI work (ref. 14) for the types of tool
geometry referred to in table 3 and table 4.
32
Table 6 – Tool Geometry Recommendations (ref. 14)
Carbide-tipped
Number
High Speed Steel
Chipbreaker
angle
(°)
clearance angle
(°)
tool normal
rake (°)
clearance
angle
(°)
0
0
6
5
8
1
8
6
10
8
2
8
6
10
8
4
8
6
10
8
5
12
6
14
8
70
6
20
6
25
8
50
7
20
6
25
8
8
20
6
25
8
(Tables 3& 4)
tool normal
rake
(°)
50
20
Table 7 – Speeds and feeds for turning
High Speed Steel
Carbide Tipped Tools
Material Group
Material Group
Compax
Diamond
1
2
3
1
2
3
Speed,
sm/m
90-200
45-90
22-45
120-300
120-180
75-180
Feed
mm/rev
0.15-0.5
0.4-0.9
0.4-1.0
0.4-0.65
0.4-0.75
0.4-0.75
Cut mm
1-3
1-3
1-3
1.1-3
1.1-3
1.1-3
90-200
45-90
22-45
150-450
150-300
90-240
300-800
Feed
mm/rev
0.07-0.4
0.015-0.4
0.15-0.5
0.15-0.4
0.15-0.4
0.2-0.4
0.05-0.15
Cut mm
0.4-0.75
0.4-0.75
0.4-0.75
0.4-0.75
0.4-0.75
0.4-0.75
0.1-0.3
Roughing
Finishing
Speed
sm/m
For copper alloys, compax diamond tools are usually used with a back rake of +10° to +20° and
a side rake of +5° to +20°.
On small-diameter lathe work the alloys in Group 1 are usually machined at the highest practical
spindle speed, the feed being adjusted to suit such conditions as depth of cut, available power,
coolants, and finish requirements.
For larger work on lathes, heavy boring mills, etc. where high cutting speeds are not practicable,
speeds should be near to the lower end of the suggested limits.
High efficiency with carbide tipped tools is attained by using a light feed, a moderately heavy
depth of cut, and the highest cutting speed consistent with satisfactory tool life. The speeds and
33
feeds given in Table 7 are typical for copper and copper alloys and are based on a depth of cut
of about 1.0 to 3mm per cut for roughing and 0.4 to 0.75mm for finishing. A starting point may
be taken as half-way between the limits given and the speed can be adjusted upwards or
downwards until the best results are obtained.
Chipbreaker Tools
Many of the Group 3, non-free-machining materials such as high-conductivity copper normally
give long ribbons of unbroken swarf when turned. Where this causes problems with swarf
clearance it is possible to vary tool geometry by adding a chipbreaking ridge behind the cutting
edge in order to give the short, broken swarf characteristic of free-machining materials when the
following conditions are met:
•
An exit angle (between the chip and the bar axis) of 20 to 60°.
•
A suitable chip curler is on the tool with a geometry that prevents the chip from reverting to
a flat, continuous strip.
If the correct land width can be selected according to the methods reported by Staley et al (ref.
3), even oxygen-free copper can be machined without difficulty. The tool geometry for this type
of work is critical and is best determined using the SIR Diagram shown in Figure 6. It is evident
that there is a direct relationship between the chip thickness or rigidity and the land width. As
chip thickness is directly related to the feed, it follows that the feed is directly related to the land
width. From basic cutting considerations, both tool geometry and cutting conditions can alter
chip thickness so that, in order to maintain a constant chip thickness, the feed would have to be
altered accordingly.
Figure 5 – Diagram showing land width and chip breaker tool action
These factors are put together in the 'SIR-diagram' to act as a rough guide or starting point for
machinists to allow them to manufacture tools for cutting high conductivity coppers with
controlled or broken swarf.
34
The first box shows the actual feed on the left. Increasing the side cutting edge (approach)
reduces the chip thickness, causing the same effect as a decrease in the feed. The values
examined were the extremes of 0° and 35°, values for intermediate angles can be interpolated.
As cutting speed is increased, the chip thickness decreases, giving the same effect as decreasing
the feed. Depth of cut will limit the choice of feed due to it having a large influence on the exit
angle; thus as the depth of cut increases, the feed will also have to increase to maintain an exit
angle in the range 20-60°. Further to this, a large nose radius will be required when cutting with
large depths of cut to achieve the exit angle requirement. The 'nose radius box' is therefore
incorporated to show the minimum nose radius for a given depth of cut; i.e. where the 'feed' line
crosses the wavy curve, read off the nose radius.
Box 5 shows that increasing the combined rake will reduce the chip thickness, thus giving the
same effect as decreasing the feed. When machining high-conductivity coppers, the use of low
rake angles within ranges 2-6 and 4-8° would promote thick chips and deformation (collar)
ahead of the tool. Therefore tools with a combined angles >50° are recommended. The final box
shows the direct relationship between the feed top scale and the land width. Note that, due to the
various factors across the diagram, the diagram, the actual feed is not the same as the feed in the
final box; i.e. the final box is a 'modified feed'. The diagram only gives a rough estimate of the
cutting parameters and tool geometry required for chip curling in copper cutting and must be
used in conjunction with the exit angle requirement of 20-60°. The diagram is likely to be
different for other materials. The example shows that a feed of 0.125mm/rev, a cutting speed of
400 sfpm (130sm/m, a depth of cut of 1.7mm, a nose radius of 0.5mm and a combined side and
back rake of 40° are best served by a land width of 3.75mm.
Cutting parameters need to be carefully maintained as the tool geometry takes in to account the
expected amount of build-up of metal on the tool. The advantage of easier swarf clearance may
be slightly offset by an increase in tool wear because of the greater compression of the swarf by
the chipbreaker. Further consideration of the effects of chipbreaker geometry is included in the
DKI publication (ref 14)
Figure 6 – SIR diagram for determining chip breaker parameters
35
Cutoff tools
For most cutoff tools, high speed steel is satisfactory for use with most of these materials.
Straight tools normally have sufficient taper for side clearance and need to be ground only for
top rake where required, and on the front end for the necessary clearance in the cut.
Circular cutoff tools are normally used in automatic screw machines since the work is usually of
small diameter and because the tool frequently cuts off into drilled or tapped holes. The design
of the cutting edge shown in the diagram has several advantages. Top rake on circular tools is
the same as for straight-blade tools; a side clearance of 0.5 to 1° is sometimes used for deep
parting operations or if, with some materials, there is a tendency towards binding. Speeds used
are about the same as for HSS form tool operations, best results being obtained with a relatively
high cutting speed and a feed of from 0.015 to 0.04mm/rev. A suitable lubricant should always
be used.
Figure 7 – Circular and straight cutoff tools
Form tools
For HSS form tools the speeds and feeds are controlled by the width of the tool in relation to the
work diameter, the amount of overhang and the shape of the contour. Feeds of 0.025 to 0.075
mm/rev should be used for roughing and 0.012 to 0.05 mm/rev for finishing, the speed being
adjusted to suit. Ample lubricant is needed. The cutting angles and clearances suggested in the
drawings are based on the use of high speed steel or carbon steel form tools.
The front clearance of a circular form tool depends principally on the diameter of the tool. It is
usually 7 to 12°, but it can be accentuated by grinding the cutting edge of the tool below centre,
then raising the toolholder so that the cutting edge is on the centre line of the work. It is
important to bear in mind that the contour of a machined part will be the exact reverse of the
form tool only when all cutting edges are parallel with the centre line of the work and of the
form tool.
36
Drilling
Where the volume of work does not call for use of special drills, standard carbon-steel or highspeed steel drills (with clearance and point angles as supplied by the manufacturer) can be used
for drilling alloys in Groups 1 or 2. When ground as suggested in Figure 8, they can also be used
for the alloys and coppers in Group 3.
The helix angle of a standard twist drill is usually between 26 and 30°, but varies, according to
the manufacturer and the diameter of the drill. Flattening the cutting edges as suggested will
overcome any tendency of the drill to pull into the metal.
High-speed steel drills of special design are frequently used in regular production work. Flat and
straight-flute drills, having a natural zero-degree rake angle, are widely used for drilling alloys
in Groups 1 and 2, particularly in automatic lathe work. The slow-spiral or 'brass' drill, with a
decreased helix angle ranging from 10° to 22° and with wide, polished flutes and a thin web,
provides large chip clearance with a decreased rake angle. It is often used for deep-hole drilling,
for auto turning work, and other high-speed drilling operations on Groups 1 and 2 alloys.
The point angle and lip clearance shown in Figure 8 can be used on all types of drills.
All copper alloys are occasionally drilled dry, but better results are obtained when a suitable
lubricant is used. As the alloys in Group 1 are produced principally in rod form for use in
automatic screw machines, a lubricant is ordinarily used.
A lubricant is desirable when drilling Group 2 alloys, particularly for deep holes and where
accuracy is necessary. A lubricant should always be used when drilling Group 3 alloys and
coppers.
Hand feeding is frequently used for shop drilling and feeds exceed those normally used for mild
steel. For alloys that work-harden easily, such as annealed aluminium bronze, keep the drill cutting
continuously to prevent glazing. The drill should be kept cutting, without interruption, as long as
chips are being ejected. In holes that are deep in relation to drill diameter, back off occasionally for
chip relief, especially if no lubricant is being used.
Many factors control the speed in drilling operations, e.g. diameter of drill, wall thickness, depth of
hole, but general recommendations are given below.
Table 8 – Speeds and feeds for drilling
Speed
sm/min
Feed
mm/rev
Group 1
60-150
0.005-0.075
Group 2
25-75
0.075-0.5
Group 3
15-40
0.075-0.5
For groups 2 and 3, the feed range suggested, 0.075 to 0.5 mm/rev is for drills from 3 to 20 mm
diameter. The lighter feeds are used with the smaller drills, for deep holes, and where it is
necessary to maintain accuracy. Larger drills can take proportionately heavier feeds, especially
the oil-tube type, where lubrication is supplied under pressure. If carbon steel drills are used
speeds should be halved.
37
Figure 8 – Drill point and clearance angles
Tapping
Possibly the principal reason for torn threads or broken taps is the selection of a tap drill which
is either too small or too close to the size of the root diameter. In the majority of cases where a
specified thread fit is not needed, and where the depth of hole is at least equal to the diameter of
the tap, a 75 per cent to 80 per cent depth of thread is sufficient. A 100 per cent thread is only 5
per cent stronger than a 75 per cent thread, yet it needs more than twice the power to tap and
presents problems of chip ejection and makes it necessary for the tap to be specially designed
for the particular alloy.
For hand tapping the alloys in Groups 1 and 2, and where the quantity of work or nature of the
part does not permit use of a tapping machine, regular commercial two and three flute highspeed steel taps should prove satisfactory. The rake should be correct for the metal being cut
and the chamfer should be relatively short so that work-hardening or excess stresses do not
result from too many threads being cut at the same time.
High speed steel taps with ground threads are used in machine tapping. In instances where the
threads tend to tear as the tap is being backed out, a rake angle should be ground on both sides
of the flute.
For machine tapping of alloys in Groups 1 and 2, regular two, three, or four flute taps with
narrow lands, deep, polished flutes, and a two or three thread chamfer are usually satisfactory.
For the metals in Group 3, particularly copper, the nickel silvers and copper-nickel, which
produce tough, stringy chips, spiral pointed taps with two or three flutes are preferred for
tapping through holes or blind holes drilled sufficiently deep for chip clearance. These taps
produce long, curling chips, which are forced ahead of the tap.
Spiral fluted bottoming taps can be used for machine (and hand) tapping of blind holes in
copper and all types of copper alloys, and wherever adequate chip relief is a problem.
The suggested rake angles and tapping speeds should serve as a starting point and they can then
be modified for the particular conditions of the job. The speeds indicated are based on the use of
taps to produce fine to moderate pitch threads. Appreciably lower speeds should be used for
coarse pitch threads, and speeds should be reduced by about 50 per cent if carbon steel taps are
used.
38
Table 9 – Tapping speeds
Speed
sm/min
Group 1
45-75
Group 2
20-45
Group 3
10-20
On automatic lathes that are working upon Group 1 alloys, maximum spindle speed is
frequently used when tapped holes are of relatively small size, or where the thread has a fine
pitch.
Figure 9 – Spiral pointed tap
Reaming
Practically all standard types of hand and machine reamers can be used successfully on copper
materials. Straight-flute reamers with narrow lands and polished flutes are commonly used, but
on some types of work they have a tendency to chatter. Standard spiral-flute reamers with a
helix angle of between 7 and 12° will overcome chatter and produce a smoother finish.
Left-hand spiral and right-hand cut reamers give excellent results either for straight or tapered
holes in all three groups of alloys.
Depending on the diameter, length of hole, and wall thickness, high-speed steel reamers can be
used at the following speeds and feeds:
39
Table 10 - Reaming speeds and feeds
Speed
Feed
sm/min
mm/rev
Group 1
up to 60
0.2-1.0
Group 2
22-45
0.2-1.0
Group 3
20-30
0.2-1.0
Figure 10 - Typical stub auto reamer
Circular, radial, and tangential thread chasers for self opening die heads and tap chasers on
collapsible taps can be used for internal and external threading of copper, brass, and bronze on
all types of automatic turning machines and a variety of horizontal and vertical threading
machines. Cutting fluid should be used for all thread chasing operations.
The rake angles and clearances indicated in Figure 11 should be modified by the relation of the
pitch to the diameter of the thread, the thread form, the thread fit needed, and other special
considerations. The cutting speeds suggested are for threads of moderate pitch.
Table 11 – Speeds for thread chasing
Speed
sm/min
Group 1
30-45
Group 2
15-27
Group 3
3-9
40
On automatic lathes that are working upon Group 1 alloys, maximum spindle speed is
frequently used when threading small diameter work or fine pitch threads.
Figure 11- Chasers for die heads and collapsible taps
Milling
Practically all commercial types of milling cutters can be used to machine copper, brass, or
bronze. Because of the wide variety of cutters available and the diverse nature of milling
operations, the cutting angles and clearances suggested in Figure 12 are fundamental and should
be modified to meet job conditions.
For copper alloys, as a general rule, the clearance behind the cutting edge should be sufficient to
prevent a rubbing or burnishing action. Excessive vibrations and digging in are usually
indications of too much rake or clearance, and sometimes of too high a speed.
Coarse tooth spiral cutters with a helix angle of 20 to 30° and helical cutters with a helix angle
of up to 53° have a shearing action that tends to resist digging in, even on the free cutting alloys
of Group 1. With adequate rake and clearance, and with land width held to a minimum, these
cutters produce fine finishes on all three groups of alloys, even at coarse feed and high speeds.
Staggered tooth, side milling cutters with alternate spiral teeth are used for deep slotting
operations, particularly on Group 3 alloys. Spiral fluted end mills are fast cutting and produce a
better finish than end mills with straight flutes.
Double angles on the back of the teeth, as shown in Figure 12, are normally used for regrinding
and give the cutting edges adequate clearance and strength. The clearance angle should be
41
greater for small cutters than for large ones and the maximum clearance angles given are for
cutters about 75 to 100mm diameter.
Only the face of the tooth is ground when resharpening form and gear cutters. This is done
radially, or in line with the centre, to preserve the cutting form of the tooth. On this type of
cutter the clearance remains constant without grinding.
The surface speeds recommended are based on the use of high-speed steel cutters with a suitable
cutting fluid. (For carbon steel cutters, reduce the speed by about 50 per cent). In many
instances these speeds may be increased several hundred per cent, depending upon such
variables as depth of cut, width of cutter, machine rigidity, desired finish, and rate of feed,
which may vary from 0.15 to 6.0 or more metres per minute.
Table 12 – Speeds for milling
Speed
sm/min
Group 1
60-75
Group 2
45-60
Group 3
15-45
When milling alloys in Group 3, some experimentation with clearance angles may be profitable.
Figure 12- Milling cutter rakes and clearances
Materials Selection
If there are no alternatives to the material to be machined, this section may be ignored. It lists
and discusses the various coppers and copper alloys commonly available. More details of
compositions, properties and applications are given in other CDA publications (ref. 19, 20)
42
High speed machining brass
High speed machining brass will be first choice material if machinability is a paramount
consideration. It can be machined consistently at rates that keep production costs very low and
make components costs very competitive. As has been shown in the earlier section on costings,
components made of brass can be made at lower total production cost than similar items made
of other materials of lower first cost.
Besides being cost-effective, free-machining brass comes with good strength, excellent high
temperature ductility and reasonable cold ductility, good conductivity, excellent corrosion
resistance, good bearing properties and low magnetic permeability. It has an attractive yellow
colour but can be plated if required.
The material contains about 58% copper and 38% zinc, with an addition of 3 or 4% of lead to
give the high-speed, free-machining quality that produces swarf that clears easily from the tool
and with minimal energy requirements. It is readily available from all good stockists in small
quantities and also from manufacturers in economically larger quantities tailored if necessary to
meet special requirements. The British Standard designations are CZ121Pb4 and CZ121Pb3. In
European national and CEN standards there will be new, computer friendly, material numbers
applicable or alternatively the compositional designations CuZn38Pb4 and CuZn39Pb3 will be
used.
The 4% lead alloy was developed some years ago and shows better machinability than the 3%
material, especially when being drilled. In the original work (ref. 4), it was clearly established
that it is necessary to use properly controlled production methods in order to make a good
product. These apply to any good free-machining brass and include a continuous casting
technique including rapid cooling in order to keep the insoluble lead globules finely dispersed.
Rapid solidification also has the advantage of retaining in solution any iron and silicon
impurities that might otherwise precipitate out to form hard particles in the brass that would
accentuate tool wear. Preheating for extrusion should also be for as short a time as possible.
These reasons emphasise why material should be obtained from reputable sources. Such
manufacturers can also, if required, carry out non-destructive eddy-current and/or ultrasonic
testing to verify that every length of material is internally sound.
Rod for Free-machining purposes
A new European standard is being published covering materials intended primarily for
economic machining operations. It has been prepared following consultations between
manufacturers, who well know their customers' main requirements, and leading users. It
includes the main materials already standardised in European countries with some modifications
made in the light of recent experience. Tolerances are included for all dimensions and for twist
and end chamfer. As with all standards, these represent normal commercial practice and
manufacturers are normally able to meet special requirements by arrangement.
The types of materials included are shown in Table 13 and cover a wide range of requirements
from those where machinability is of paramount importance to others where a combination of
properties is needed. Following the principles included in ISO 197, the CEN/ISO designation
gives a good general idea of the composition using the usual chemical abbreviations, a list of
which is included in Appendix 1. The main alloying additions are listed, generally in descending
order, and the remainder of the alloy is copper. More details on properties, available forms and
remarks regarding usage of these and other materials are in Table 3 and Table 4 for wrought and
cast materials. The new numbering system for CEN materials will, when published, facilitate
computer recognition of the materials.
43
Materials with an existing BS designation listed are likely to be more easily available in the UK
than others. The others may be available from specialist stockists or, in economic quantities,
from manufacturers.
Coppers and Copper Alloys
As mentioned previously, there are many different coppers and copper alloys available to meet
the need for a very wide variety of types and combinations of mechanical and physical
properties. In order to achieve the right balance of properties that suit particular applications, it
has often been necessary to tailor materials specially for the purpose. Machinability is just one
of the factors to be considered when choosing the right material for a particular product. All
attributes have to be considered and balanced when choosing the most cost-effective way of
producing a component to suit a purpose and lifetime.
Coppers
Coppers of commercial purity, such as are used for electrical purposes are mainly specified for
the manufacture of components when there is a need for their high conductivity, corrosion
resistance and ductility. Because of their softness, they are not the easiest to machine though not
difficult using recommended procedures. However, additions of other elements such as sulphur,
tellurium or lead may be made to produce 'free machining coppers' with only a slight effect on
conductivity. Similar considerations apply to the deoxidised pure copper used for water service
tubing, water cylinders, pressure vessels and other applications requiring excellent welding or
brazing properties.
Small additions of chromium, zirconium, beryllium and other elements are used to produce
high-strength high-conductivity alloys, many of which can have their properties further
improved by heat treatment. For the production of electrodes for resistance welding a common
material is copper-chromium which can have an addition of sulphur to improve machinability.
All these alloyed coppers can be machined satisfactorily with experience.
When machining copper-beryllium alloys, care should be taken that the material does not
overheat and give off toxic fume. Normal turning, drilling and similar operations are considered
safe provided that adequate lubricant is used. Operations such as grinding without lubricant or
welding should be avoided unless approved fume extraction equipment is used. Appropriate
advice is available from suppliers.
Many of the alloyed coppers, such as those containing chromium, zirconium and beryllium,
achieve their high strengths and relatively high electrical conductivities from precipitationhardening after a solution heat treatment. These alloys retain their strengths at temperatures
where other high conductivity copper alloys tend to soften. Advice should be sought from the
manufacturer concerning the changes in machinability and dimensional tolerances brought
about as a result of the heat treatments.
Brasses
Brasses are the most commonly used copper alloys. The addition of zinc strengthens the
material and incidentally changes the colour to a yellow or gold effect. The ratio of copper and
zinc can be varied for advantages and the addition of other elements gives still more variety of
combinations of properties such as machinability, strength, hardness, ductility (hot or cold),
conductivity and corrosion resistance as well as many others.
44
Lead additions are used to improve machinability. The lead is insoluble in the solid brass and
segregates as small globules that help the swarf to break up in to small pieces and may also help
to lubricate the cutting tool action. The addition of lead does, however, affect cold ductility
which may control both the way in which material is produced and the extent to which it can be
post-formed after machining. Additions of manganese, iron, aluminium, silicon and other
elements are used to increase strength and hardness while tin, aluminium and arsenic are used to
further improve the good corrosion resistance of brasses, making them suitable for use in more
aggressive environments.
The additions of lead for improved machinability have been made for many years. Such brasses
are standard for the manufacture of water fittings and give years of satisfactory service in all
closed-circuits such as central heating systems and in the majority of fresh water supplies.
Generally such fittings give no cause for concern when used for fresh water for drinking
purposes but in certain well-known areas the supply water can be aggressive to brass and the use
of a material that is immune to dezincification (such as cast gunmetal) or dezincification
resistant (such as CZ132, CuZn36Pb2As) is recommended for service above ground and
mandatory for underground fittings.
Nickel-Silvers
Nickel-Silvers are copper-nickel-zinc alloys similar in many respects to the brasses but with
even better corrosion resistance. They have a silvery colour that is dependent on the nickel
content and are well known because of their usage for electro-plated nickel silver (EPNS)
decorative tableware. They also have significant usage as wire or strip in hard tempers used for
springs and relay contacts. Leaded versions are available where free-machining rods are
required and for hot stampings.
Bronzes
Bronzes are alloys of copper and tin. In the UK they are generally deoxidised with phosphorus
which improves strength and hardness and the alloys are then known as phosphor bronzes.
They are used for bearings and gears. In wire and strip form they have good elastic properties
and are used for contacts. Lead is often added to improve machinability and to improve bearing
properties. Gunmetals are alloys of copper, tin and zinc. They are readily cast and have good
machinability and good corrosion resistance. They are used for pumps, bearings, valves and
"bronze" statuary.
Copper-nickel alloys and the Aluminium Bronzes
Copper-nickel alloys and the Aluminium Bronzes were both developed for service in severe
marine environments. The copper-nickel alloys are very ductile and suitable for the manufacture
of plate, sheet and tube that combines the resistance to biofouling of copper with a corrosion
resistance in fast-flowing seawater that is significantly better. Additives to improve
machinability would have a disastrous effect on properties such as weldability and are therefore
very uncommon. With experience, copper-nickel alloys can be machined with greater ease than
alternative materials such as stainless steels.
There are a wide range of available aluminium bronzes, mostly as casting alloys but some are
suitable for hot working by rolling, forging or extrusion. Only those with a low alloy content
can be cold worked to a significant extent. The strength and corrosion resistance of these alloys
is excellent, being even better than most other common copper alloys in marine environments.
Lead can be added to improve machinability but this is not included in most standard
specifications because of its adverse effect on other properties.
45
When rough machining aluminium bronze castings it is important that the initial cut is heavy
enough to get through the cast surface in one operation and that carbide tipped tooling is used.
This is because the surface oxide contains alumina which is extremely abrasive. The
machinability of this type of alloy is generally not so good as the free-machining brasses but
still much better than other materials, especially most stainless steels. For general and finish
machining, fine grain plain carbide tools are recommended. Steel-cutting grade carbides (e.g. P
types) and titanium nitride coated tools are not recommended.
Notes
Hardness
The hardness (or temper) of all wrought materials can have a marked effect on machinability.
As a general rule, soft materials are not so easy to machine as harder ones of similar
composition but this does not necessarily apply to free machining grades. It must also be
remembered that any heat treatment subsequent to machining may affect dimensional
tolerances.
Dimensional tolerances and straightness
Dimensional tolerances and straightness of machining rods will normally be in accordance with
appropriate standards unless otherwise agreed. Small diameter material is naturally sensitive to
handling techniques; care is needed to avoid distortion in transit or storage. Ends of rods may be
chamfered at one or both ends by arrangement to facilitate entry in to automatic machines.
Dimensions
Dimensions may be affected if a material is in a highly stressed state before machining, or even
when machining induces such stresses. Relief of internal stress can lead to distortion of
components otherwise machined within tolerance. Retained internal stresses in cold worked
starting stock can be removed before machining by an appropriate stress-relief anneal. For
details of suitable treatments, please see CDA publications relevant to the materials being
machined.
Table 13 – Materials commonly available as rods for free-machining purposes
Alloy Designation
ISO/CEN
Nearest BS
Equivalent
CEN Material
Number
Remarks
Free-machining coppers (see text for notes regarding improved machining techniques for the usual high-conductivity coppers
using chipbreaking tools.)
CuSP
C111
CW114C
Free-machining copper-sulphur is the preferred highconductivity copper for turning. Containing no tellurium or
lead,it is also more amenable to recycling.
CuTeP
C109
CW118C
Copper-tellurium is often preferred to copper-sulphur for
deep-hole drilling work.
CW113C
Leaded free-machining copper.
CuPb1P
46
Table 13 (continued)
Alloy Designation
ISO/CEN
Nearest BS
Equivalent
CEN Material
umber
Remarks
Brasses - Copper-zinc alloys, generally with a lead addition
These brasses have excellent machinability but very limited cold workability. They are used where subsequent bending or riveting
is not important.
CuZn38Pb4
CZ121Pb4
CW609N
British high-speed machining brass
CuZn39Pb3
CZ121Pb3
CW614N
Standard European free-machining brass for which the100%
machinability rating was established
CuZn36Pb3
CZ124
CW603N
Higher copper content gives better ductility which means
thebrass can be cold drawn to higher tensile strengths.
Equivalentto ASTM C36000, the standard US free-machining
brass
CuZn40Pb2
CZ122
CW617N
Most popular alloy for hot stamping and high-speed machining
These brasses contain 2% lead and have good machinability and some cold workability. Workability increases with increasing
copper content (and corresponding decrease in zinc content):
CuZn39Pb2
CZ120
CW612N
CuZn37Pb2
CZ131
CW606N
CuZn38Pb2
CZ128
CW608N
Good machinability but ductility lower than CZ131
These brasses contain about 1% of lead and are machinable and have good to very good workability:
CuZn39Pb1
CZ129
CW611N
CuZn38Pb1
CZ129
CW607N
CuZn35Pb2
CW601N
CuZn35Pb1
CW600N
CuZn39Pb0.5
CZ137
CW610N
This brass was specially developed for the manufacture of water fittings for use with supply waters. It is resistant to
dezincification, has good machinability and some cold workability:
CuZn36Pb2As
CZ132
CW602N
Special brasses, including the free-machining versions of some brasses with improved corrosion resistance and others of higher
strength.
CuZn36Sn1Pb
CZ112
CW712R
CuZn36Pb2Sn1
CZ134
CW711R
Leaded Naval brass
CuZn40Mn1Pb1
CZ136
CW720R
Brass for architectural sections
CuZn37Mn3Al2PbSi
CZ135
CW713R
High tensile brass with silicon
CuZn40Mn1Pb1AlFeSn
CZ114
CW721R
High tensile brass (free-machining type)
CuZn40Mn1Pb1FeSn
CZ115
CW722R
High tensile brass (free-machining type, low aluminium)
47
Table 13 (continued)
Alloy Designation
ISO/CEN
Nearest BS
Equivalent
CEN Material
umber
Remarks
Leaded Nickel Silvers (Copper-nickel-zinc alloys) These are the free-machining versions of the alloys that are notable for their
silvery colour, good resistance to corrosion and good strength. The alloys become whiter in colour with increasing nickel content:
CuNi18Zn19Pb1
NS113
CuNi12Zn30Pb1
CuNi10Zn42Pb2
CuNi7Zn39Pb3Mn2
CW408J
CW406J
NS101
CW402J
CW400J
Free-machining wrought bronzes (Copper-tin alloys):
CuSn4TeP
CW457K
Free-machining phosphor
bronze
CuSn4Pb2P
CW455K
Free-machining phosphor
bronze
CuSn5Pb1
CW458K
Free-machining bronze
CuSn4Pb4Zn4
CW456K
Machining preforms made by hot stamping or forging
Both of these processes involve hot working of material cut to a suitable size; forging is
generally between flat, open hammer faces while hot stamping involves the use of shaped dies.
Forging gives a good fine-grained non-directional structure and is suitable for short runs. The
expense of shaped dies is justified by a reduction in product costs because of reduced machining
and faster production rates. Dies may be two-part or include extra cores that reduce still further
the amount of machining required. Hot stamped components have a good surface finish that
usually needs machining only where holes, threads or mating faces are required.
Table 14 shows all the materials likely to be included in the European standard, classified
according to general availability throughout Europe and hot working characteristics. Those with
a pre-existing BS designation are likely to be the easiest to obtain within the UK.
Most of the leaded duplex brasses and high-tensile brasses are readily hot stamped at moderate
temperatures to close tolerances, causing little die wear. Choice will depend on the properties
required by the end use and material availability. Tough pitch copper is fairly easy to hot work
but needs to be at a higher temperature.
The free-machining coppers are too brittle at elevated temperatures to be easy to hot work,
though open forging is possible with care. Similar remarks apply to the high-conductivity
alloyed coppers and copper alloys.
Duplex aluminium bronzes can be hot worked, again they need to be pre-heated to a higher
temperature than the brasses. With care, the copper-nickel alloys shown can be readily hot
worked provided that impurities do not cause hot shortness. The leaded nickel brasses shown
are the preferred choice when nickel silvers are required.
48
Table 14 – Materials for hot stampings and forgings
Generally Available
Available to Special Order
Alloy Designation
ISO/CEN
Alloy Designation
Nearest
BSEquivalent
CEN
Material
Number
Machinability
Group
ISO/CEN
Nearest BS
Equivalent
CEN Material
Number
Machinability
Group
CZ108
CW508L
2
-
CW712R
2
These materials are very readily hot worked:
CuZn40
CZ109
CW509L
2
CuZn37
CuZn38Pb2
CZ128
CW608N
1
CuZn38Pb1Sn1
CuZn39Pb2
CZ128
CW612N
1
CuSn39Sn1
CZ133
CW719R
2
CuZn39Pb3
CZ121-Pb3
CW614N
1
CuZn39Pb0.5
CZ137
CW610N
2
CuZn40Pb2
CZ122
CW617N
1
CuZn39Pb1
CZ129
CW611N
1
CuZn39Pb2Sn
-
CW613N
1
CuZn23Al6Mn4Fe3Pb
-
CW704R
2
CuZn40Pb1Al
-
CW616N
2
CuZn35Mn2Ni2Al1Pb
-
CW710R
2
CuZn40Pb2Sn
-
CW619N
2
CuZn40Mn1Pb1
CZ136
CW720R
2
CuZn36Pb2As
CZ132
CW602N
1
CuZn40Mn2Fe1
-
CW723R
2
CuZn37Mn3Al2PbSi
CZ135
CW713R
2
CuZn37Pb1Sn1
CZ134
CW714R
2
-
CW718R
2
CuZn40Mn1Pb1AlFeSn
CZ114
CW721R
2
CuZn40Mn1Pb1FeSn
CZ115
CW722R
1
CuZn39Mn1AlPbSi
49
Table 14 (continued)
Generally Available
Available to Special Order
Alloy Designation
ISO/CEN
Alloy Designation
Nearest BS
Equivalent
CEN Material
Number
Machinability
Group
ISO/CEN
Nearest
BS
Equivalen
t
CEN Material
Number
Machinability
Group
These materials are less easy to hot work:
Cu-ETP
C101
CW003A
3
Cu-HCP
-
CW021A
3
Cu-OF
C103
CW008A
3
Cu-DHP
C106
CW024A
3
CuAl8Fe3
CA106
CW303G
3
CuAl6Si2Fe
-
CW301G
3
CuAl10Fe3Mn2
CA105
CW306G
3
CuAl7Si2
CA107
CW302G
3
CuAl10Ni5Fe4
CA104
CW307G
3
CuAl9Ni3Fe2
-
CW304G
3
CuAl11Fe6Ni6
-
CW308G
3
CuAl10Fe1
-
CW305G
3
These materials are also hot workable:
CuCr1Zr
CC102
CW106C
3
CuBe2
CB101
CW101C
3
CuNi2Be
-
CW110C
3
CuCr1
CC101
CW105C
3
CuNi2Si
-
CW111C
3
CuCo1Ni1Be
-
CW103C
3
CuNi10Fe1Mn
CN102
CW352H
3
CuCo2Be
C112
CW104C
3
CuNi30Mn1Fe
CN107
CW354H
3
CuZr
-
CW120C
3
CuNi1Si
-
CW109C
3
CuNi3Si
-
CW112C
3
CuNi7Zn39Pb3Mn2
-
CW400J
1
CW402J
1
CuNi10Zn42Pb2
50
NS101
Materials for Castings for Subsequent Machining
Gunmetals are the most common cast copper alloys. They are a range of copper-tin-zinc-lead
alloys with good castability and machinability. Compositions are again varied to suit end-use
requirements. Other common cast materials include the leaded bronzes, phosphor bronzes,
leaded phosphor bronze and aluminium bronzes. These are detailed in Table 4.
Material Availability
All the standardised coppers and copper alloys are listed in Tables 3 and Table 4, which gives
common designations, commonly available forms and some guidance on properties, applications
and machinability considerations. The materials listed include most of those generally available
in Europe and believed to be made by at least two manufacturers. Highlighted are those most
easily available in the United Kingdom.
The tables include machinability ratings for each material.
Group 1 alloys
In Group 1 will be found mainly the brasses and coppers with additions made specifically for
use where machining will be one of the most important manufacturing operations.
Group 2 alloys
In Group 2 are the coppers and alloys produced to meet combinations of property requirements
including some such as cold formability that are not prominent in Group 1 materials. This
improvement is effected by the change in structure from homogenous to duplex which occurs
when the zinc content exceeds 37 per cent. Since lead also increases machinability it is added to
alloys in this group in quantities up to 1 per cent. Post-machining operations such as flaring,
bending, thread-rolling, and severe knurling often require additional ductility to prevent
fracturing. Hence the lead addition is limited to effect a compromise.
Some of the alloys in this Group are, by their composition and structure, intended to satisfy
certain corrosive service or strength requirements. Although they do not contain lead the duplex
structure gives good machinability.
Group 3 alloys
Group 3 alloys have machinability ratings of less than those of Group 2. They are either coppers
or alloys in which corrosion resistance, strength, or colour properties are more important than
machinability.
The low zinc alloys - 90/10 brass (CZ101), 85/15 brass (CZ102) and 80/20 brass (CZ103) - are
often referred to as gilding metals. They are attractive in colour and are used for many
ornamental objects. The hardware industries make many articles from these alloys.
The other alloys in this group have a wide variety of uses. Copper-cadmium is a high-strength
alloy which is used for such electrical applications as terminals and connectors. The phosphor
bronzes, which contain copper, tin and small amounts of phosphorus, are strong and tough as a
group.
51
More information on the original British material specifications can be found summarised in
CDA Technical Notes(ref, 19, 20), and fully described in the relevant British Standards. These
are BS2870-2875, covering copper and copper alloys in wrought, semi- manufactured forms,
and BS 1400 'Specification for copper alloy ingots and copper and copper alloy castings'. As
previously mentioned, these are due to be superseded by relevant common European
specifications, given BS numbers.
Spreader for an expanding mandrel for a coiler for a rolling mill or wire rod mill
(Westley Brothers plc)
This large casting in aluminium bronze to BS 1400 AB2 is being machined to precise dimensions.
52
Illustrations - Cast Preforms
Water Meter Casing
(Delta EMS Ltd)
This is produced from a complex, thin walled, pressure die
casting to close tolerances. Minimal machining is then required.
Valve - sectioned to show
internal structure
Sprue of precision cast brass keys
for a musical instrument
(Saunders Valve Co Ltd)
An elaborately cored shell moulding is used to make this valve.
Machining is then only required on mating faces and for
threading.
(Boosey & Hawkes Ltd)
Precision casting allows components to be produced to very
intricate shapes. Minimal finish machining is then required.
A selection of continuously cast shapes
(Delta Encon Ltd)
Continuous casting using the ENCON process produces bars of material with particularly good, uniform mechanical properties.
Complex cross sectional shapes can be made to high precision. Where surfaces have to be machined, an allowance of less than
1mm can be used because of the exceptionally sound surface characteristics of the con-cast material.
53
Illustrations – High Precision
Fire Extinguisher Valve
(Hawke Components Ltd)
This fire extinguisher valve is designed so that it can easily be removed from the pressure cylinder when
refilling takes place. It is produced from 35mm diameter bar using a series of drilling, tapping, boring
and milling operations. The use of brass is cost-effective because of the dramatic savings in machining
costs over those for steel.
Motor Commutator
(Parvalux Electric Motors Ltd)
This small motor commutator is diamond turned to very close tolerances ensuring minimal brush wear in
service.
54
Bearing Cages
(RHP Industrial Bearings Ltd)
These bearing cages are machinined to high precision tolerances from extruded brass hollow bar giving the
reliability required for heavy duty bearings in high speed applications.
Aluminium Bronze Screw Connectors
(Balcombe Engineering Ltd)
High precision components in phosphor bronze and aluminium bronze for naval applications.
Connectors for Digital Exchanges
Copper-Tellurium Electrodes
(Greenpar Jubilee Ltd)
(Graphite Technologies plc and Incast Precision
Engineers for Finecast (Maidenhead ) Ltd)
The central part of the connectors are machined
from beryllium copper originally supplied as solid
hexagonal rod, the rest being brass. The whole
connector is finally gold plated to ensure complete
contact and correct conductivity.
A selection of EDM electrodes produced in
Tellurium-Copper. The use of Cu-Te saves up to
30% machining time compared with hard-drawn
high conductivity copper, and also has the
advantage of a completely burr-free finish.
55
Illustrations – Repetition Jobs
Terminals
(Greenpar Jubilee Ltd)
These miniature electronic terminals are made to a high
standard of precision and reliability by the million.
Live and neutral pins for 13 amp plug
(Tenable Screw and Delta Extruded Metals Ltd)
Production is simplified and material is saved by
the use of a shaped, extruded bar for the pins. The
extruded bar is sliced, the pin tip is finished and the
top is drilled and tapped for the connector screw.
Plastic insulation is then added.
Riveted electrical components
(Crabtree Electrical Industries Ltd)
These components are made from CZ131 brass and
are shown at production stages after extrusion, after
machining and after riveting. The components are
very reliable in service and ecomomical to
manufacture in high volumes
Water and gas pipeline fittings
(Currie and Warner Ltd)
This picture shows the variety of components which can be manufactured by fast repetition machining. One component is
sectioned to reveal the internal detail.
56
Illustrations – Short Runs
Spring Case and Primary Gear
for a Carriage Clock
(Biddle & Mumford Gears Ltd)
This component is quickly and economically machined from
solid brass bar. Efficient swarf recovery ensures costeffective manufacture.
'A' Frame for a Skeleton Clock
(Biddle & Mumford Gears Ltd)
These components are CNC milled to close tolerances. Short
runs are economically possible because of the short time
needed to reset a CNC machine.
Copper Electrodes for EDM
(University of Birmingham School of Manufacturing and Mechanical Engineering and the IRC in Materials for High
Performance Applications)
The picture shows two solid copper electrodes (centre) which were used to make the two halves of the forging die (top) by
electro discharge machining. The finished forging made using the dies is shown at the bottom.
The electrodes are made from C101 high conductivity copper because of its high conductivity and ease of machining. They
are produced using CNC machinery to ensure repeatability and an accuracy of about +0.013 mm. Using a high precision
copper electrode allows the manufacture of a forging die by EDM to an accuracy of +0.025mm which in turn can be used to
produce high accuracy components requiring minimal finishing.
57
Machining a contractor piece from CZ 121 brass on a Worth Graffat rotary
transfer machine at Swissmatic Ltd
(Swissmatic Ltd and Kuwait Petroleum Lubricants Ltd)
The operations involved include sawing, drilling, tapping and broaching. The lubricant is Q8 Neat Oil
Bach NQ.
Pneumatic Assemblies
Model Railway Components
These components are made by silver soldering
together two separately formed and machined parts
and then bending the assembly to shape.
Short runs of special purpose items for model kits
are easily and economically made from brass.
58
Illustrations – Machining HC Coppers
End rings for an electric motor
Components for Power Industry
(Thomas Bolton Ltd)
(Thomas Bolton Ltd)
These rotor rings and end rings are precision machined from
copper-chromium which has good creep strength and
conductivity at the operating temperature.
The cost of these large, complex items is minimisComponents for
ed by making near-to-net shape preforms by forging or casting in
free machining copper. Complex machining operations are then
easily performed to a high standard of accuracy.
Chip breaker tool
(Dr. M Staley, BNF-Fulmer)
Overhead view of a high-conductivity copper bar being machined at 150m/min, showing the chip curler tool
promoting chip breaking.
A selection of components machined from high
conductivity copper, electronic grade
Welding Nozzles
(Flame-Equipment Ltd)
(Dawson Shanahan Ltd)
These welding nozzles are drilled with very fine, deep holes. The
preferred material for such components is copper-tellurium
because of its excellent thermal conductivity and the ease with
which it can be drilled.
Specially developed high-precision machining techniques are
used to produce these components cost-effectively in oxygen-free
copper, Cu-OFE. The items in the foreground are semiconductor
heat sinks for use in diodes and thyristors for large current
applications. The items with the narrow slots are interruptors for
emergency power switching. The carefully machined slots
control the electric arc which forms as the contact is broken.
59
Machinability Testing Methods
There is no method of assessing machinability that is equally applicable to all machining
operations since materials behave differently. It is accepted, for instance, that of the two popular
free-machining high conductivity coppers, copper-sulphur is better for turning operations while
copper-tellurium is preferred for deep hole drilling.
There are however, two main methods of classifying material machinability properties. One is
an assessment of the type of swarf generated, an important property since the reliable operation
of automatic equipment is dependent on swarf clearing easily and not obstructing the tooling or
clogging lubricant filters. The other involves assessing the rate at which tooling wears and needs
to be replaced, a factor that affects productivity significantly. Other criteria of interest include
power requirements and surface finish.
Fundamental work on quantifying machinability is mainly based on the work initially reported
by Taylor (ref. 5) in 1906 and subsequent work such as those by Ernst and Marchant (ref. 6) .
These are discussed in standard textbooks such as that by Trent (ref. 7) and Smith (ref. 18) and
in many other papers. Many absolute and ranking tests have been summarised by Mills and
Redford (ref. 8).
A previous CDA publication (ref. 9) issued in 1939 is recognised as the first really useful guide
to machining copper and its alloys. An article published in 1943 (ref. 10) first classified coppers
and copper alloys according to a combination of chip shape, surface finish and power
requirements. The standard free-machining brass at that time was given an arbitrary standard
rating of 100% and all other coppers and alloys related to that. Since then there has been
considerable work on other, non copper-based, materials which has resulted in a profusion of
100% base ratings. There has also been the development of the improved high-speed machining
brass containing more lead that was given a 150% rating. The figures are a meaningful guide to
performance but must be used with discretion in the light of the many variables that affect
machinability. A subsequent CDA publication (ref. 11) classified the materials in to just three
broad groups but recent work (ref. 3) has shown that the use of chipbreaker tools can make the
machining of some of the group 3 materials relatively easier.
In discussing machinability, the large number of variables must be borne in mind. Some of
these are:
•
Material variables - Composition (more than 140 wrought and 40 cast materials) and
internal structure as affected by casting technique, fabrication methods, thermal history and
product form.
•
Machining operation - Single point turning, form tool turning, drilling, milling, tapping,
broaching, etc.
•
Machining variables
Tool material, tool geometry (several variables), speed, feed rate, available power, lubrication
techniques and machine variables (such as rigidity).
Multiplication of all these as a preliminary to assessing all their inter-variable effects results
in a sum that is at least financially indigestible. However much work has already been done
by a number of workers and it is hoped that soon there will be available a knowledge base
summarising what has been published (ref. 12).
The work at BNFMRA (subsequently BNF-Fulmer that introduced the 4% lead high-speed
machining brass was reported by Davies (ref. 4). It included a study of the existing brasses
commonly used world-wide. Testing, see Figure 13, was by means of large scale machining
60
trials involving five operations including single-point turning, form tool turning, centring,
drilling and parting off. The results gave a better understanding of the compositions,
impurity effects and material production factors affecting machinability that has been
widely adopted by leading manufacturers.
Figure 13 - Geometry of component and schematic diagram of machining operations in tests conducted
by Davies (ref. 4)
Following the establishment of an ASTM universal machinability test (ref. 13), Thiele et al have
reported (ref. 1) on the comparative machinability of three brasses, two steels and a freemachining aluminium alloy and established a universal machinability index. This is used on an
automatic lathe and involves the production of a part using rough and finish form tool work
together with drilling two different diameters and parting off. The test is neither simple nor
inexpensive, see Figure 14, but does yield a commercially relevant rating suitable for both
materials selection decisions and machine shop costings. The results gave the rankings shown in
Figure 2 and resulted in the development of a nomograph to help estimate production rates.
61
As a further extension of this work it was possible to obtain comparative costings of many
industrial components made in both free-machining steel and free-machining brass (ref. 2).
Despite the extra initial cost of the brass, the overall cost savings, shown in Table 1 were
significant and resulted in production being switched to brass. This was even without
consideration of the further saving to be made by the lack of need for a further plating operation
that is normally required to protect steel parts from corrosion in storage and service.
The work published by the Deutsches Kupfer Institut (DKI) (ref. 14) , referred to earlier and in
the main tables, includes a comprehensive review of the main factors affecting the machinability
of coppers and copper alloys. Swarf types are characterised and illustrated and detailed
guidance recommendations given for the machining characteristics of many materials. There is a
useful summary of the common formulae used in evaluating and costing machining operations.
It is available from the DKI in German or in English translation from CDA Information
Department.
The machining of conventional tough pitch and oxygen-free high conductivity coppers is of
great interest because the free-machining grades of high conductivity copper are not so readily
available or inexpensive as the free-machining brasses. Copper is traditionally cut with a higher
rake angle and the use of more lubricant than brass in order to produce a cleaner chip and thus a
better finish by preventing deformation ahead of the tool. Conventional tools tend to give swarf
that is generated in long spirals and may obstruct the machine. Samandi and Wise (ref. 15) and
Staley et al (ref. 3) described work that investigated the use of chipbreakers of various types.
The SNMG-61 geometry shown in Figure 15 was amongst the most useful of commercial tips
available. A relationship was established that gave the best chipbreaker geometry to suit the
material and cutting conditions.
Figure 15 SNMG-61 style sintered-in chip breaker tool investigated by
Samandi and Wise (ref. 15), gave the best chip breaking performance with
unleaded 60/40 brass (CZ109).
62
A recent report on the machinability of copper based alloys by Samandi and Wise (ref. 15)
covered the characteristics of a range of alloys using single point turning to investigate tool
force, chip thickness, tool temperature, tool wear and chip form. The materials investigated
included:
CuZn30 (CZ106 70/30 or cartridge brass),
CuZn40 (CZ109 60/40 unleaded duplex brass),
CuZn40Pb2 (CZ122 leaded brass)
CuZn36Pb2As (CZ132 dezincification resistant brass)
CuZn14Si4 (silicon brass to UNS C87500)
Three leaded gunmetals, including CuSn5Pb5Zn5 (85/5/5/5 gunmetal)
CuNi10Fe1Mn (CN102 90/10 copper-nickel),
CuNi30Mn1Fe (CN107 70/30 copper-nickel)
CuAl10Ni5Fe4 (CA104 duplex aluminium bronze) and
CuAl6Si2Fe (CA107 aluminium-silicon bronze).
As expected the unleaded brasses formed continuous chips throughout the 25-600m/min
cutting speeds investigated although self chipbreaking can be achieved except at very low
feed rates. A chipbreaker tool can be used with advantages when self chipbreaking is
unstable. For these materials, there was no advantage in using titanium nitride coatings on
HSS tools.
The leaded brasses formed discontinuous chips; there was also a significant reduction in
tool forces due to the lubricity of the lead. The possibility of lead smearing across the
machined surfaces was thoroughly investigated. At cutting speeds up to 700 m/min it could
occur but was easily removed with acetic acid or an ultrasonic clean. An interesting
observation was that the amount of surface lead was reduced by using tools with a large
nose radius or by using worn tools, whereas rake angle had little effect. Leaded gunmetals
with more than 1% of lead also gave free-machining discontinuous chips and could be
machined at speeds of up to 360m/min.
The duplex aluminium bronze gave segmented chips when cut at speeds over 25m/min but these
could give high force fluctuation causing the need for a tough tool. Aluminium-silicon bronze
showed a lower cutting force, allowing higher metal removal rates. For the aluminium bronzes it
was also shown that tool materials should not contain or be coated with titanium compounds
since a reaction causes quick failure of the tool. Carbide tipped tools containing 10% cobalt and
0.8µm size tungsten carbide particles are preferred.
The copper-nickel alloys produced continuous chips under all cutting conditions. For these
alloys the use of a coating of titanium nitride reduced tool force and almost doubled tool life.
Some work has been carried out on the development of suitable lead-free brasses (ref. 16) for
possible use in countries where environmental considerations are onerous but as yet there is no
satisfactory substitute. Most free-machining brass is made from recycled scrap containing lead
and alternatives would therefore be significantly more expensive if excluding the use of this
material supply.
It is generally agreed that further work is needed to develop a cheap and effective universal test
for machinability ratings.
63
Cutting Fluids for Copper Alloys
As previously described, the machinability of copper and its alloys varies from Group 1 (free
cutting alloys) through Group 2 (readily machined alloys) to Group 3 (difficult-to-machine
alloys and coppers). The effect of machinability on tooling, feeds, speeds and the depth of cut
have already been discussed. These machinability ratings and the machining operations have
also to be considered in order to select the most cost-effective cutting fluid.
Functions of cutting fluids
It is generally accepted that the primary functions of a cutting fluid are to cool and lubricate the
tool and therefore:
•
lengthen tool life and/or permit high metal removal rates
•
produce a good surface finish
•
reduce cutting force
In addition, the cutting fluid performs a number of important secondary functions such as:
•
cooling the chip and workpiece and hence assisting in maintaining dimensional accuracy
•
carrying swarf away from the cutting zone
Care is taken when formulating a cutting fluid to ensure no undesirable side effects are
encountered and in particular that the cutting fluid is:
•
non corrosive to workpiece and machine tool components - while copper alloys do not rust,
some can be easily stained.
•
stable during its service life
•
easily drained or washed from the components.
•
non toxic and non irritant
•
readily disposable when exhausted
For some applications cutting fluids may be required to have particular characteristics such as
transparency and compatibility with machine lubricants.
The influence of cooling on tool life can be vital. Water is an excellent cooling medium and is
therefore an obvious constituent where cooling is a prime requirement. For many operations,
mineral oils properly directed and applied in ample quantity do provide sufficient cooling. The
most effective form of lubrication is where two sliding surfaces are completely separated by an
oil film. However, in the cutting zone, due to the high pressures necessary to shear metals and
resultant high temperatures involved in the majority of cutting operations, this situation is not
encountered, therefore load carrying and friction reducing additives have to be incorporated.
Laboratory tests and field experience have proved additives incorporated in cutting fluids are
effective in prolonging tool life and maintaining a good surface finish.
Selection and application of cutting fluids
The relative importance of the functional requirements of cutting fluids depends upon the
machining characteristics of the workpiece, the type of cutting tool material and the nature of
the machining operation. These various effects are outlined in the following sections.
64
Type of work material
With free machining alloys of Group 1, which produce short chips, cooling of the tool is seldom
necessary although cooling of the work may be necessary in certain applications. In addition,
lubrication between the flank of the tool and the workpiece may increase tool life. The hard
brasses and bronzes of Group 2 require a balance between cooling and lubrication whilst with
the ductile materials of Group 3 which produce long continuous chips, lubrication will be the
main consideration.
Effect of Tool Material
In machining operations with single-point tools, such as turning, boring, shaping and planing,
the choice of cutting fluids is to some extent influenced by the cutting tool material employed.
When using carbide tipped tools at moderate speeds, the cutting may be performed dry but
lubricant such as water-soluble fluid can be used rather than neat oil to prevent fuming or haze
generation at the higher operating speeds. Invariably the use of a cutting fluid will permit
increases in speed, feed and productivity, improve surface finish, improve tolerances and
lengthen tool life.
High speed steel tools require efficient cooling unless very low speeds are employed. Best
results will be achieved at high speed by using a cutting fluid which combines both cooling and
lubricating properties.
Type of machining operation
Lubricants should be selected carefully with respect to the machining characteristics of the
operations. Regular quality checks should be carried out with a simple hand-held refractometer
to ensure that the cutting fluid is within specification.
In drilling, the chief functions of a cutting fluid are cooling and the removal of swarf, whereas
for precision finishing operations, particularly those with expensive tools such as reamers,
taps, discs, broaches, milling cutters and hobs, lubrication is more important.
For milling and hobbing, however, a cutting fluid with excessive lubricity should be avoided
since it may cause the cutting edges to slide over the work surface during the initial part of the
cut.
For reaming, the cutting fluid should be of low viscosity to effectively flush away the chips,
since any accumulation will cause the reamer to bind and may produce scored and oversize
holes.
Type of cutting fluid
Of the variety of cutting fluids that are available, many are recommended by their manufacturers
for use in the machining of copper alloys.
Watermix cutting fluids. Watermix cutting fluids fall into two main groups, soluble oils and
synthetic cutting fluids.
Soluble oils These are mixed with water to form emulsions of oil in water. They consist of
blends of mineral oils, emulsifying agents and other additives which stabilise the emulsion and
prevent corrosion. The oil droplet size determines whether the emulsion is of the milky or
translucent type.
65
Emulsions provide maximum cooling with limited lubricating properties as they are used at
high dilutions. Typically 3 to 10% of fluid is used, giving oil to water ratios from 30 to 10 : 1
for general machining operations.
To enhance their lubricating properties, soluble oils may also incorporate fatty oils or extreme
pressure additives.
Care should be taken in preparation of these emulsions, in particular when mixing, the oil
should always be added to the water.
Synthetic and semi-synthetic cutting fluids. These form true or colloidal solutions when
added to water, they consist of water soluble corrosion inhibitors and surface active load
carrying materials. Fully synthetic products contain no mineral oil, however, there are some that
do contain a small percentage of mineral oil, these are known as semi-synthetic cutting fluids.
During use some watermix cutting fluids may be depleted of oil or additives whilst others may
be more concentrated by the evaporation of water. It is desirable to check the dilution's strength
frequently and to make adjustments in accordance with the manufacturer's recommendations.
The dilution strength can usually be readily checked by refractometer.
All watermix cutting fluids tend to become contaminated with fine swarf, tramp oil and other
extraneous matter and regular supervision and monitoring of their condition is advisable. They
should also be checked for bacterial degradation although copper and copper alloys do provide
some protection.
Neat cutting oils. Neat cutting oils are used without addition of water. They consist of refined
mineral oils containing proportions of extreme pressure additives and in many cases, selected
fatty oils.
The extreme pressure activity of neat cutting oils should be controlled according to the type of
metal to be worked and the nature of the machining operation. All extreme pressure lubricants
must balance lubrication performance against staining characteristics particularly in the case of
copper based alloys.
The design of automatic and semi-automatic machine tools is frequently such that it is difficult
to exclude cutting fluids completely from enclosed gear systems and therefore neat oils are
usually favoured for such machines. Careful choice of the neat cutting oil shows that no ill
effects result from the intermixing of machine lubricants and the cutting lubricants. In many
cases a common grade will satisfy both needs.
Neat cutting oils may or may not contain special-purpose additives. Generally mineral oils have
now completely replaced animal and vegetable oils as the latter are less stable in use.
Compounded oils. The main reason for the inclusion of additives in neat cutting oils is that in
some machining operations the load carrying properties of a straight mineral oil are inadequate
for the severe conditions experienced in the cutting zone. Small additions of fatty oils such as
animal or vegetable oils improve lubricity and the cutting oils reinforced in this way are known
as compounded oils.
These compounded oils are particularly useful in the machining of difficult copper alloys and
give excellent tool life and good surface finish without staining.
EP Oils. For the more difficult machining operations even the compounded oils cannot give the
lubrication performance required and neat oils containing EP (extreme pressure) additives have
to be used. EP cutting oils usually contain additives based on sulphur or chlorine or a
combination of both and are recognised as necessary where the highest degree of lubricating
efficiency is required. Sulphur can be present in two forms, active or inactive. In the mild or
inactive type of fluid it is chemically combined with a fatty oil additive which is blended with
66
mineral oil to produce a sulphurised fatty oil. The active version contains sulphur in elemental
form dissolved in mineral oil and is generally referred to as a sulphurised mineral oil. In general
the presence of free or elemental sulphur is undesirable when copper and its alloys are to be
machined as it tends to blacken the surface. Chlorine is usually present as a chlorinated paraffin
which is blended sometimes singly with mineral oils and sometimes in combination with fatty
oils and sulphurised additives. Where staining is to be avoided inactive neat oils containing
sulphur, chlorine or fat can be used. However care should be taken to clean the finished
component as soon as possible after machining and to ensure that the swarf is free from such
contaminants before resale. An inactive oil is defined as one which will not darken a copper
strip immersed in it for 3 hours at 100° C.
Excess lubricant in swarf can be removed in a centrifuge to recover the lubricant and obtain a
better return on the scrap. When metal swarf is being recycled it is normal practice to remove
residual lubricants with heat before remelting is possible. This results, of course, in the
evolution of gases from any lubricant residues.
Chlorine-free lubricants When scrap is being recycled, the presence of any residual
undesirable chemicals such as chlorine can cause environmental hazard. Where required, many
manufacturers are now able to supply chlorine-free lubricants that prevent this problem.
Lubricant Manufacturers’ Recommendations
Table 15 should be used as a guide to grades of cutting fluids recommended by some of the
leading companies in the industrial oil field. More information can be obtained from individual
companies, who can also advise on any health precautions that may be required in use.
67
Table 15 – Lubricant manufacturers’ recommendations
For neat oils and water-miscible lubricants suitable for materials in machinability groups 1, 2 and 3 (or all ( ) materials)
Note: If swarf is to be sold for recycling, please see text regarding the need for lubricant to be free from chlorinated additives.
(These are sample recommendations only, consult manufacturers' literature for full details)
Autos
CNC
Turning
Form
Tool
Turning
Drilling
Boring
Broaching
Tappping
Milling
Sawing
1
1
1
1
1
1
1
1
1
BP Oil 7395
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
BP Oil 7332
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
3
3
3
3
3
3
3
3
Grinding
NOTES
BP OILS UK LTD
Neat Oils
Bezora 120
Low viscosity, additive free,
recommended for free-cutting
materials
Dilutable
Syncut 32
General purpose emulsion,
3-5%.
Long life micro-emulsion, 35%.
3
Oil-free high performance
heavy duty fluid. 4-10%.
CASTROL (UK) LTD
Neat Oils
Ilocut 462
Highly fatted, mineral oil
blend specific for coppersand
copper alloys, low in active
sulphur.
68
Autos
CNC
Turning
Form
Tool
Turning
Drilling
Boring
Broaching
Tappping
Milling
Sawing
Grinding
NOTES
Ilocut 482
Fatty/mineral oil blend, with
chlorinated additive,
recommended for copper
alloys.
Ilocut 486
Fatty mineral oil blend with
chlorinated
additiverecommended for
coppers and copper alloys.
Dilutable
Cooledge CB
Specifically formulated for
coppers and copper alloys. 2.5
- 10% concentration
Hysol G
2-4% concentration, see
manufacturers
recommendations.
CENTURY OILS LTD
Neat Oils
Coppacent 1
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
Mineral oils with non-staining
Coppacent 2
sulphurised additives
Kloricent 2
Mineral oil with non-staining
chlorinated additives.
Walcut B2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
Chlorinated EP
Walcut 36
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
mineral oils
Walcut 927
69
Autos
CNC
Turning
Form
Tool
Turning
Drilling
Boring
Broaching
Tappping
Milling
Sawing
Grinding
NOTES
Dilutable
Epicent B
Non-phenolic EP. 3-10%
Supercent C
Nitrite & phenol free, 3-7%
Clearcent N
DE LA PENA LTD
Neat Oils
560
Low viscosity chlorinated.
570
Medium viscosity sulphochlorinated with inactive
sulphur.
585
Very low viscosity for honing
and super-finishing.
Dilutable
750
Nitrite & phenol-free EP
750
soluble oils, 2-4%
ITW DEVCON
Dilutable
Safetap
Safemist
Synthetic, 7%
70
Autos
CNC
Turning
Form
Tool
Turning
Drilling
Boring
Broaching
Tappping
Milling
Sawing
Grinding
NOTES
Safesystem
1000
5%
Safesystem
2000
5%
ELF OILS LTD
Neat Oils
Elfcut BB22
Medium viscosity with fatty
additives, non-staining.
Etirelf CB26
Medium viscosity, high
proportion of fatty additives
for heavy duty machining.
Aleda ED22
Chlorinated oil.
Dilutable
Sarelf ABS
Non-phenolic mineral oil. 4%
recommended.
ESSO PETROLEUM CO LTD
Neat Oils
Dortan N12
Suitable for cam-operated high
speed automatics
Dortan N13
Low viscosity EP oil for
medium to heavy automatics.
71
Autos
CNC
Turning
Form
Tool
Turning
Drilling
Boring
Broaching
Tappping
Milling
Sawing
Grinding
NOTES
Dortan N14
Chlorinated, sulphur additives.
Heavy machining, low
staining.
Dortan N55
Low viscosity with synthetic
fatty additive.
Dilutable
Aquarius
Aquarius EP
1
1
1
1
1
1
1
1
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
3
3
Aquarius EP
Plus
General purpose, 3-5%
Chlorinated, 5-10%
3
3
Aquarius EPT
Suitable for more ductile
materials. 3-10%
Recommended for more
arduous machining operations.
10%
GULF OIL
Neat Oils
Gulfcut BN
Gulfcut EN
Gulfcut FN
Gulfcut ENX
anti-misting grade
Dilutable
Gulfcut Cascade
200
1
1
1
1
1
72
1
1
Biostable semi-synthetic, 26%
Gulfcut Cascade
300
Autos
CNC
Turning
Form
Tool
Turning
Drilling
Boring
Broaching
Tappping
Milling
Sawing
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
Grinding
NOTES
Biostable semi-synthetic 310%
Gulfcut Cascade
350
Biostable semi-synthetic EP, 310%
HOUGHTON VAUGHAN PLC
Neat Oils
Cindolube 3100
1
1
1
1
1
Cindolube 3101
1
1
1
1
1
Neat cutting oil
1
1
Neat cutting oil
Dilutable
Solcut CB
Mineral oil blend with additives,
3-5%
Hocut B60 CB
Non-staining biostable EP, 5%
Q8 - Kuwait Petroleum Lubricants Ltd
Neat Oils
Q8 Bach NK
1
1
1
1
1
1
1
1
1
1
Q8 Bach NC
2&3
2&3
2&3
2&3
2&3
2&3
2&3
2&3
2&3
2&3
Q8 Bach NP
Dilutable
Q8 Beethoven T
Conventional oil based
Q8 Beethoven SC
Conventional oil based, EP
73
Autos
CNC
Turning
Form
Tool
Turning
Drilling
Boring
Broaching
Tappping
Milling
Sawing
Grinding
NOTES
Q8 Beethoven
VNF
Semi-synthetic biostable
Q8 Beethoven
XUA
semi-synthetic biostable
MOBIL OIL Co
Neat Oils
Mobilmet 424
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
Anti-mist chlorine-free grades
Mobilmet 427
2&3
2&3
2&3
2&3
2&3
2&3
2&3
2&3
2&3
2&3
Mobilmet 120
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
Mobilmet 151
3
3
3
3
3
3
3
3
3
3
nitrite-free grades. 3-10%
Solvac Double
1
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
5%
Solvac 57
3
3
3
3
3
3
3
3
3
3
3%
1&2
1&2
1&2
1
1
1
1
1
1
1
All chlorine free
2&3
2&3
2&3
2&3
2&3
2&3
2&3
2&3
2&3
2&3
Dilutable
Non-phenolic, chlorine &
OVOLINE LUBRICANTS
Neat Oils
Ovomet GP
Ovomet HP
Ovomet LV
74
Autos
CNC
Turning
Form
Tool
Turning
Drilling
Boring
Broaching
Tappping
Milling
Sawing
Grinding
NOTES
Dilutable
Novamet S
Semi-synthetic ester based for
Estramet
light/medium machining,
chlorineand nitrite free
SHELL OILS
Neat Oils
Macron B
1&2
1&2
1&2
1&2
1&2
1&2
1&2
Non-staining medium viscosity
Macron C
3
3
3
3
3
3
3
Higher additives than Macron B
Macron F
EP oil
Dilutable
Dromus B
SRO
SRO EP
Non-phenolic, nitrite free.
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
3
3
3
3
3
3
3
3
2&3
2&3
2&3
2&3
2&3
2&3
2&3
Non-phenolic, nitrite-free
With EP additives
SMALLMAN LUBRICANTS LTD
Neat Oils
Crowncut 822
2&3
Dilutable
75
2&3
Medium viscosity fatty
chlorinated oil.
Turning
Form
Tool
Turning
Drilling
Boring
Broaching
Tappping
Milling
Sawing
Grinding
Crownsol S170B
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
1&2
Conventional soluble oil. 4-5%
Crown Novasol
265
3
3
3
3
3
3
3
3
3
Semi-synthetic cutting fluid. 45%
Autos
CNC
NOTES
TEXACO LTD
Neat Oils
Cleartex Plus 32
Non-chlorinated EP specially
developed for machining copper
and its alloys
Metalworking oil
32
Chlorinated EP. Fatty with
inactive sulphur. For use where
good surface finish is required.
Dilutable
Aquatex HB
General purpose biostable. 2.55%
Aquatex H3
EP version of Aquatex HB for
improved surface finish. 2.5-5%
TOTAL OIL GREAT BRITAIN LTD
Neat Oils
Scilia L
Non-additive cutting oil
Scilia B
Non-staining EP oil
76
Autos
CNC
Turning
Form
Tool
Turning
Drilling
Boring
Broaching
Tappping
Milling
Sawing
Grinding
NOTES
Dilutable
Lactua HP2
EP cutting oil. 2-10% Coppers
and copper alloys should be
cleaned after machining
WYNN OIL (UK) LTD
Neat Oils
Titalub 13
Perfolub 40
Special lubricant for difficult
work
Dilutable
Microcool 387
Semi-synthetic recommended
for copper & copper alloys.
Microcool 440
WF 370
Contocool 805
Synthetic
77
Addresses of Lubricant Manufacturers
BP Oil UK Ltd, Kensington House, 136 Suffolk Street, Queensway, Birmingham B1 1LW
Castrol (UK) Ltd., Burmah Castrol House, Pipers Way, Swindon, Wilts. SN3 1RE
Century Oils Ltd, PO Box 2, New Century Street, Hanley, Stoke-on-Trent ST1 5HU
De la Pena Ltd, Racecourse Road, Pershore, Worcs WR10 2DD.
ITW Devcon, Brunel Close, Park Farm, Wellingborough, Northants., NN8 6QX
Elf Oil Ltd., Olympic Office Centre, 8, Fulton Road, Wembley, Middx HA9 0ND
ESSO Petroleum Co Ltd., Ermyn Way, Leatherhead, Surrey, KT22 8UX
Gulf Oil, The Quadrangle, Imperial Square, Cheltenham. GL50 1TF
Houghton Vaughan plc., Legge Street, Birmingham B4 7EU
Kuwait Petroleum Lubricants Ltd, Knowsthorpe Gate, Cross Green Industrial Estate, Leeds LS9
0NP.
Mobil Oil Company, Mobil House, 54-60 Victoria Street, London SW1E 6QB
Ovoline Lubricants, Pipewellgate, Gateshead, Tyne & Wear. NE8 2BN
Shell Oils, Industrial Sales Centre, Cobden House, Station Road, Cheadle Hume, Cheshire, SK8
5AD
Smallman Lubricants Ltd, Great Bridge Street, West Bromwich, West Midlands B70 0DE
Texaco Ltd., 1, Knightsbridge Green, London SW1X 7QJ
Total Oil Great Britain Ltd., Commercial Marketing Dept., Charles House, 17-23 Vaughan
Road, Harpenden, Herts. AL5 4DY
Wynn Oil (UK) Ltd. Unit 3, Headly Park 9, Headly Park East, Woodley, Reading RG5 4SG
78
References
(1)
E W Thiele et al, "Comparative Machinability of Brasses, Steels and Aluminium alloys:
CDA's Universal Machinability Index", SAE Technical Paper 900365, February 1990,
Copper Development Association Inc, New York.
(2)
"Free-cutting brass for lower screw machine product cost", six product information
sheets, 1991, Copper Development Association Inc, New York, USA. See CDA
Publication No 100 Brass Beats Steel.
(3)
M A Staley, E F Smart and M L H Wise, "The Machining of High Conductivity
Coppers", INCRA Project 343A Final Report, Nov 1984, International Copper
Association.
(4)
D W Davies "Improved free-machining leaded brass: Part 1 Summary Report" British
Non-Ferrous Metals Research Association (Now BNF-Fulmer) Research Report RRA
1778, April 1971. BNF-Fulmer, Wantage.
(5)
F W Taylor "On the art of cutting metals", Trans ASME 28, 31, 1906.
(6)
H Ernst and M E Merchant, "Chip formation, friction and high quality machined
surfaces", Surface Treatment of Metals, ASM 29, 299, 1941.
(7)
E M Trent, "Metal Cutting", 3rd Edition, Butterworth, London, 1991.
(8)
B Mills and A H Radford, "Machinability of Engineering Materials". Applied Science
Publishers, London & New York, 1987.
(9)
"Machining Copper and its alloys", CDA Publication No 34, 1939, Copper Development
Association (Out of Print).
(10) "Machining copper and its alloys", Met Ind 65, 1944, p373.
(11) "Machining Copper and its alloys", CDA Technical Note TN3, 1970, Copper
Development Association (Out of Print).
(12) R Francis and D W Davies "Proposal for the preparation of a knowledge base on the
machining of copper and its alloys". Private communication.
(13) "Standard test method of evaluating machining performance of ferrous metals using an
automatic screw/bar machine", ASTM E618, American Society for Testing and Materials,
Philadelphia, USA.
(14) "Richtwerte fuer die spanende Bearbeitung von Kupfer und Kupfer legierungen".
("Factors Affecting the Machining of Copper and Copper alloys") DKI i 18, 1983,
Deutsches Kupfer Institut, Berlin. (Available in English translation from CDA)
(15) M Samandi and M L H Wise, "Machinability of Copper Based alloys", INCRA Project
384 Final Report, March 1989, International Copper Association.
(16) J T Plewes and D N Loiacono, "Free-cutting copper alloys contain no lead", Adv Mat &
Proc., 1991, Oct, pp23-27.
(17) "Machining of Copper and Copper alloys". ASM Handbook Vol 16, 9th Edition, 1989.
(18) G. T. Smith, 'Advanced Machining: The Handbook of Cutting Technology', 1989. 281pp.,
IFS Publications, UK
79
(19) 'Copper and Copper alloys: Compositions and Properties', CDA Technical Note TN10,
1986, 28pp. (See also CDA Datadisc D1)
(20) 'Copper and Copper alloy Castings: Properties and Applications' CDA Technical Note TN
42, 40pp, 1991. (See also CDA Datadisc D3)
(21) 'Cost-Effective Manufacturing - Process Selection', CDA Datadisc D4, 1992.
(22) R Bakerjian, Tool and Manufacturing Engineers Handbook, Vol 4, Design for
Manufacturability, pp11.3-11.5 (source: Carboloy Systems Div), Society of
Manufacturing Engineers, Dearborn, Michigan.
Copies of INCRA Reports (now ICA) can be obtained from International Copper Association,
260 Madison Avenue, New York, NY 10016, USA,
Additional data on specific machining operations, tools and techniques may be obtained
from the following:
Production Engineering Research Association (PERA), Melton Mowbray Leicestershire
LE13 OPB.
Machine Tool Industry Research Association (MTIRA), Hulley Road, Macclesfield, Cheshire
SK10 2NE.
also individual machine tool manufacturers for recommendations for specific copper alloys.
Lists of copper alloy manufacturers and stockists obtainable from:
Association of Bronze and Brass Founders, Heathcote & Coleman, 136 Hagley Road,
Edgbaston, Birmingham B16 9PN. (cast product manufacturers)
British Non-Ferrous Metals Federation, 10, Greenfield Crescent, Birmingham B15 3AU.
(wrought product manufacturers)
80
Copper Development Association
5 Grovelands Business Centre
Boundary Way
Hemel Hempstead
HP2 7TE
Website: www.cda.org.uk
Email:
helpline@copperdev.co.uk