This document discusses cutting fluids used in machining processes. It provides an introduction to cutting fluids, including their history and types. The main types discussed are straight oils, soluble oils, synthetic fluids, and semi-synthetic fluids. The document also covers the chemistry and desirable properties of cutting fluids, as well as literature on cutting fluid application methods such as flood cooling, mist application, and cryogenic cooling. It discusses the functions, applications, selection, advantages, and disadvantages of cutting fluids and their environmental effects.

1. Cutting Fluids for Machining
By:
Abdirahman Said Dhore
Abdullahi Abubakar Ahmed
Abdullahi Hashi Salad
A project report submitted in full filament of the
Requirements for the machine tool course
School of Engineering
Department of electromechanical
Somali national university

2. ii
DECLARATION
We hereby declare that the work in this project is our own except for quotations and summaries
which have been duly acknowledged.
Date: Nov/2019
Name Registartion number Contact:
Abdirahman Said Dhore B1EN27 Abdirahmansaciid04@gmail.com
Abdullahi Abubakar Ahmed B1EN34 Engdalmar74@gmail.com
Abdullahi Hashi Salad B1EN44 Raagehashi@gmail.com

3. iii
Abstract
In the last decades a lot has been discussed about the suitability of using cutting fluid to
cooling and lubricate machining processes. The use of cutting fluid generally causes economy of
tools and it becomes easier to keep tight tolerances and to maintain workpiece surface properties
without damages. There are various advantages of cutting fluid application as increasing tool life,
decreasing machining times and improving surface quality. However, there are some
disadvantages of cutting fluid as high costs relating storages, preparation, filtration and recycling,
pollution harmful to environment. In the other hand, it brings also some problems, like fluid
residuals and human diseases. Because of environmental and health problem some alternatives has
been sought to minimize of cutting fluid in machining operations. Various methods such as spray
application, dry machining and internally cooled have been offered in machining processes.
However, there are also situations where cutting fluid must be used, such as gear making,
broaching and honing. Therefore, topics like kinds and methods of applications of modern cutting
fluids and what are new in this area will unavoidably are considered. The results of investigations
on the development and use of methods of applying cutting fluids were given in this paper.

4. iv
Table of content page
Abstract …………………….…………………………………………………………………………… II
Table of content……………………………….…………………………………………………………. III
List of figures …………………………………………………………………………………………… VI
Chapter one
1. Introduction ………………………………………………….…………………………………. 1
1.1 History of cutting fluid ……………..………………………..………………………………… 2
1.2 Types of cutting fluid ………………..………………….……………………………………... 3
1.2.1 Straight oils cutting fluids …………………….…………………………………………. 4
1.2.2 Soluble oils cutting fluids ……..………………………………………………………….. 4
1.2.3 Synthetic cutting fluids ……….………………………………………………………….. 4
1.2.4 Semi synthetic cutting fluids.…………………………………………………………….. 5
1.3 `The Chemistry of cutting fluids……………………………………………………………….. 5
1.4 Desirable properties of cutting fluids in general are…………...…………………………… 7
Chapter two
Literature review……………………………………………………………………………………… 8
Chapter three

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3.1 Flood cooling…………………………………………………………………………………….. 11
3.2 Mist application…………………………………………………………………………………. 11
3.3 Manual application……………………………………………………………………………… 11
3.4 Cryogenic Cooling………………………………………………………………………………. 11
3.4.1 Cryogenic pre-cooling of the work-piece……………………………………………… 12
3.4.2 Indirect cryogenic cooling……………………………………………………………… 12
3.4.3 Cryogenic spraying and jet cooling method…………………………………………… 12
Chapter four
Functions and application of Cutting Fluid ………………………………………………………… 13
4.1 Function of cutting fluid…………………………………………………………………………… 13
4.1.1 Lubrication at low cutting speeds…………………………………………………… 14
4.1.2 Cooling at high cutting speeds………………………………………………………… 14
4.2 Applications…………………………………………………………………………………… 15
4.2.1 Applications Where Cutting Fluid Offers Benefits………………………………… 15
4.2.2 Applications Where Cutting Fluid Does Not Interfere in the Process……………… 15
4.2.3 Applications Where Cutting Fluid Is Negative to the Process……………………… 16
4.2.4 Application of Minimum Quantity of Fluid (MQF)………………………………… 16

6. vi
4.3 Selection of suitable cutting fluids………………………………………………………………… 17
4.3.1 Type of machining processes ………………………………………………………… 17
4.3.2 Workpiece materials…………………………………………………………………… 17
4.3.3 Cutting tool materials………………………………………………………………… 17
4.4 Advantages of cutting fluid……………………………………………………………………… 17
4.5 Disadvantages of cutting fluid…………………………………………………………………… 18
Chapter five
Environmental effects of cutting fluid………………………………………………………………… 19
5.1 Extraction and manufacturing of components……………………………………………… 19
5.2 Manufacturing of concentrate………………………………………………………………… 19
5.3 Transportation…………………………………………………………………………………. 20
5.4 Use and handling………………………………………………………………………………… 20
5.5 Recycling and reuse…………………………………………………………………………… 20
5.6 Waste and destruction………………………………………………………………………… 21
Chapter six
Conclusion……………………………………………………………………………………………… 22
References………………………………………………………………………………………………. 24

7. vii
List of figures
Figure 4.1 function of cutting fluid …………………………………………………………………… 13

8. 1
Chapter one
1. Introduction to cutting fluid
Cutting fluids are liquid used in metalworking operations for reducing friction between the
work piece and the tool and for removal of the heat generated by the friction. Cutting fluids are
used in metal machining for a variety of reasons such as improving tool life, reducing workpiece
thermal deformation, improving surface finish and flushing away chips from the cutting zone. It
also helps in shaping and cutting of metals [1].
These fluids are usually used during the cutting operations or machining. Machinery and
equipment are quite expensive and are important assets of the workshop, factory or company.
Cutting fluids are a fantastic solution to improving and increasing the life of the tools and also
reducing permanent damage to the machinery, this is done by flushing away chips from the cutting
zone and improving surface finish. These fluids come in a variety of categories like straight oils,
soluble oils, semi synthetic fluids, synthetic fluids and more. These fluids remove the corrosion
and rust from the surface of the metal of the machine and equipment and thus help in maintain
them and enhancing their efficiency and life [2].
These fluids should definitely be used if you want to maintain your expensive machinery and
equipment and also save it from permanent damage. Cutting fuels are also helpful in shaping and
cutting of metals. Thus they have multiple purposes and usages and are primarily used to sharpen
the metals and help in keeping them from away from rust and arrest corrosion. Thus it is very
advisable to go for these cutting fluids as they will help you save on maintenance cost and will
also help in increasing the life of your machinery and equipment. For some machining operations
including sawing, turning, processing, drilling and grinding, cutting fluids can be utilized to enable
higher cutting speed to be utilized, to increase the cutting tool life, and, to some degree lessen the
tool-work surface grating amid machining. The fluid is utilized as a coolant and furthermore
greases up the cutting surfaces. But, cutting fluid and coolant are two different products [3].

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There are quite a few functions performed by cutting fluid. Keeping the workpiece and tools
cool is one such function. Most of the cutting fluids utilized are fluids as extended mineral oils or
potentially manufactured fluids, which emulsify in water. These fluids can be connected as a
pumped stream or through an oil mist with the help of compressed air. Various specific machining
operations utilize infused gasses (compacted air or latent gasses). Strong or paste cutting
substances are additionally utilized which incorporate greases, pastes, waxes, soaps, graphite based
substances [4].
Cutting fluids increase the tool life and improve the efficiency of the production systems
providing both cooling and lubricating the work surface. Cutting fluids are extensively used in
drilling operations as it removes chips from inside the holes, thus preventing drill breakage. Higher
surface finish quality and better dimensional accuracy are also obtained from cutting fluids.
Cutting fluids have been widely used in machining operations in efforts to increase cooling and
lubricity, and as a result enhance tool life, reduce process variability, etc. However, over the last
decade, it has become apparent that fluid-related decisions have all too frequently been based upon
industrial folklore rather than knowledge-based quantitative evidence [5].
1.5 History of cutting fluid
In theory, water should be a good metalworking fluid. The vast majority of energy dissipated
in the metal cutting operation presents itself as heat. Consequently cooling is of the essence. At
the end of the nineteenth century water applied as a stream at the cutting tool was in fairly regular
use. However, straight water gives two very obvious and serious problems - corrosion and lack of
lubrication for both the machining operation and the machine itself [6].
The first attempts to overcome this involved mixtures of fatty oils with water, loosely coupled
by alkali. While working in a fashion, rusting was not really controlled satisfactorily, and the
inherent instability of the mixture caused great problems [6].

10. 3
During the Great War true soluble oils, as we know them now, began to be used in industry.
These are basically mineral oils or mineral fatty oil mixtures emulsified with soaps or sulphonates.
They often incorporate additional additives such as solvents or phenolic materials for stabilization,
and corrosion inhibitors [7].
As the sophistication of these products grew, variants were developed, including the fine particle
translucent emulsions commonly used in some grinding applications.
Neat cutting oils were also in widespread use then, and in fact the extreme pressure
additives incorporated into these products led to the development of the soluble oils. This
development enabled aqueous cutting media to start taking over some of the more demanding
metal cutting applications from their neat counterparts.
While the service to industry of soluble cutting oils has been, and continues to be,
substantial, the problems of bacterial attack have never been totally overcome. This attack not only
can produce the well-known unpleasant odors present in some machine shops after weekends, but,
ironically, can lead to splitting of the emulsion and lowering of the pH value, which in the end
brings us right back to the old problem - corrosion.
Incorporation of biocides and the instigation of rigorous maintenance schedules can
certainly allay the potential problems of bacterial attack on soluble oils, but the hankering doubts
present in many users' minds necessitated the development of a different approach during the
1950s. Before examining this approach in some detail, a parallel development to that of soluble
oil emulsions had been taking place, and it was the state of the art in this field which really gave
the lead into synthetics. This development is worth dwelling on.
In grinding operations the need for cooling is paramount, while the other requirements of a
general metal cutting product, such as lubricity etc are obviously not so relevant. The corrosion
problems of straight water had tended to be overcome, particularly in surface grinding operations,
by the addition of soda ash. However, over a period of time the soda ash tended to deposit out on
machine working surfaces, leading to jamming. Consequently, in the early 1950s alternatives to

11. 4
soda ash solutions were developed mostly based on alkali nitrites and organic amine mixtures in
aqueous concentrates [6].
1.6 Types of cutting fluid
There are many types of cutting fluids namely, straight oils, soluble oils, synthetic and semi
synthetic are widely used in metal cutting processes. Bio-based cutting fluids have the potential to
reduce the waste treatment costs due to their inherently higher biodegradability and may reduce
the occupational health risks associated with petroleum-oil-based cutting fluids since they have
lower toxicity. The output is a healthier and cleaner in the work environment, with less mist in the
air. For that reason, cutting fluids developed from vegetable oil in the present study are
environmentally friendly and have a good lubricating ability as compared to others [6].
1.6.1 Straight oils cutting fluids
Straight oils, so called because they do not contain water, are basically petroleum, mineral,
or age-based oils. They may have additives designed to improve specific properties. Generally
additives are not required for the easiest tasks such as light-duty machining of ferrous and
nonferrous metals. For more severe applications, straight oils may contain wetting agents
(typically up to 20% fatty oils) These additives improve the oil’s wet ability; that is, the ability of
the oil to coat the cutting tool, workpiece and metal fines. They also enhance lubrication, improve
the oil’s ability to handle large amounts of metal fines, and help guard against microscopic welding
in heavy duty machining. For extreme conditions, additives (primarily with chlorine and sulfurized
fatty oils) may exceed 20%. These additives strongly enhance the Ant welding properties of the
product.
1.6.2 Soluble oils cutting fluids

12. 5
Soluble oils (also referred to as emulsions or water-soluble oils) are generally comprised
of 60-90 percent petroleum or mineral oil, emulsifiers and other additives. A concentrate is mixed
with water to form the metalworking fluid. When mixed, emulsifiers (a soap-like material) cause
the oil to disperse in water forming a stable “oil-in-water” emulsion. They also cause the oils to
cling to the workpiece during machining. Emulsifier particles refract light, giving the fluid a milky.
1.6.3 Synthetic cutting fluids
These kind of cutting fluids do not have mineral oil in its composition. They are based on
chemical substances which form a solution with water. They are made of organic and inorganic
salts, lubricant additives, biocides, lubricant additives, among others, added to water. They have a
longer life than other fluids, because they are not attacked by bacteria and, thus, the number of
replacement in the machine tank is reduced. They form transparent solutions, what cause a good
visibility in the machining process and have additives which provide high wet ability and,
therefore, high cooling ability. The most common synthetic oils also provide good corrosion
protection. The most complex ones are of general use and, besides, good cooling ability they also
have good lubrication ability. When the synthetic fluids have only anticorrosion additives and the
EP properties are not necessary, they are called either chemical fluids or true solutions and present
good cooling properties [8].
1.6.4 Semi synthetic cutting fluids
The semi synthetic fluids have 5% to 50% of mineral oil plus additives and chemical
composites which dissolve in water forming individual molecules of micro emulsions. The
presence of a large amount of emulsifiers, compared to soluble oil, provides a more transparent
appearance to the fluid. The lower amount of mineral oil and the presence of biocides increase the
fluid life and reduce health risks, compared to the emulsions. EP and anticorrosion additives are
used like in the soluble oils. Additives which guarantee a more acceptable color for the fluids are
also used.

13. 6
1.7 The Chemistry of cutting fluids
When the metal is cut a clean nascent surface at atmospheric pressure results that is very
reactive and quickly adsorbs either by chemisorptions (strong) or physisorption (weak) any
substances (liquids or gases) in sufficiently close proximity to itself. Chemisorptions is the
adsorption onto a surface where a chemical bond such as a covalent or ionic bond forms, whereas
physisorption involves lesser forces of adhesion like van der Waals forces from polar interactions
between atoms. Depending on the cutting process used, the time available for chemical equilibrium
to establish itself on the new metal surface varies, and this could influence the performance of the
cutting fluid used. Monitoring certain cutting process parameters that will need to be determined
from the experimental results should indicate cutting fluid life. how long it takes when cutting for
the cutting fluid to stop aiding the cutting process. It does seem feasible that the cutting fluid that
is applied to the tool tip just before cutting can last for a short time as a protective film as its bond
energy from chemisorption is typically 40 to 800 kJ/mol, and the bond energies of aluminium are
typically in the region of 0.0 15kJ/mol to 57 kJ/mol. The metal- soaps that would originate are
layers that would have a lower tendency to weld than metal. Catalysis-can and often does happen
and there may be a need for the initial cutting fluid to have a specific molecular arrangement for
catalysis to occur in the metal at the interface of the tool and the shear-zone. Thus it may be
possible for similar cutting fluids to exhibit different results during cutting [9].
To provide lubricants with sufficient load carrying capacity and friction characteristics for
cold rolling of aluminium, additives are added to the low viscosity mineral base oils. These
additives are mainly fatty alcohols, fatty acids and fatty esters. Fatty alcohols ensure better
performance of the lubricant because they do not affect the annealing properties of the aluminium.
Tribochemical reactions of these additives with aluminium are very interesting. Organometallic
products result from reaction of the fatty additives with fresh unoxidised metal surfaces that

14. 7
formed during plastic deformation. These surfaces are very reactive and are called nascent
surfaces. Fatty acid soaps are well known. It is clear that esters, ethers and alcohols react with fresh
aluminium surfaces. It has been suggested that polymeric soap formation results from reaction
with esters and fatty acids, and alkoxide formation from alcohols and ethers. Fatty alcohols can
lead to a similar reaction of soap formation but to a lesser extent than fatty acids. In this case, it
was assumed that part of the alcohol was changed in to an acid which can react to give an ester
and a blend of hybrid soaps.
The cutting fluids stabilize the nascent metal surfaces by means of reacting with them. The
metal salts that form serve as a low shear strength film that reduces friction and provides improved
anti-weld properties. the resulting surface has better anti-weld properties than the unreacted freshly
formed nascent metal surface. The result is a shorter welded-zone or contact length and there is
therefore less shear, a lower cutting force and a reduced cutting temperature. When metal is cut in
a vacuum a longer contact length is observed than when it is cut in air. When air is present the
oxygen reacts with the nascent metal surface instead of the tool and this reduces the contact length.
The oxide layer on the tool does not form at the hottest region on the tool but a little further away
in the cooler region, because the oxygen in the air reacts preferably with the nascent metal surface
and is thereby removed from the cutting edge region of the tool. Similar to the oxide layer
producing a shorter contact length the cutting fluids also react with the nascent metal surface
produced in metal cutting to bring about a reduced contact length, the size of the welded zone is
reduced [10].
1.8 Desirable properties of cutting fluids in general are:
a. High thermal conductivity for cooling
b. Good lubricating qualities
c. High flash point, should not entail a fire hazard
d. Must not produce a gummy or solid precipitate at ordinary working temperatures
e. Be stable against oxidation.
f. Must not promote corrosion or discoloration of the work material.
g. Must afford some corrosion protection to newly formed surfaces.

15. 8
h. The components of the lubricant must not become rancid easily
i. No unpleasant odor must develop from continued use
j. Must not cause skin irritation or contamination
k. A viscosity that will permit free flow from the work and dripping from the chips.
Chapter two
Literature review
Cutting fluids have traditionally been used in machining operations to lubricate the chip-
tool and tool-workpiece interfaces, remove heat from the workpiece and cutting zone, flush away
chips from the cutting area, and inhibit corrosion. While each of these four functions can be
employed as justification for cutting fluid usage, it is widely believed that the primary functions
of a cutting fluid are lubrication and cooling. Seminal contributions to the technical literature in
support of this belief are provided below.
Any study on the lubricating effects of a cutting fluid builds upon an understanding of the
mechanics and forces involved in a machining process. An early method proposed to analyze a
metal cutting process was the orthogonal cutting model of Merchant. This model is based upon the
assumptions that the cutting edge is perfectly sharp, deformation is plane strain, and that the
stresses on the shear plane are distributed evenly. Their model characterizes the deformation
geometry via the shear angle, which describes the plane on which shear deformation occurs. The
forces acting on the chip at the rake face of the tool are balanced by the force acting on the chip at
the shear plane. This allows for the development of a system of force equations that can be used
to determine characteristics of the process [11].
Based upon the work of Merchant, Lee and Shaffer used plasticity theory, specifically slip-
line field theory, to develop a more sophisticated model to apply to the machining problem. Oxley
and Hastings added strain hardening into the slip-line theory and successfully applied it to predict
cutting forces. The predictive abilities of this model were shown to be extremely sensitive to the
workpiece material. A major conclusion of slip-line field modeling is that specification of rake

16. 9
angle and friction factor do not distinctively determine the shape of the chip. This is because more
than one field can be constructed, each with a different chip thickness and contact length with the
tool [12].
Further studies sought to account for the complicating issues of material behavior,
nonlinear contact, high temperature, high strain rate, and large strain in metal cutting
modeling/simulation. A great many efforts have been made to use finite element methods to
characterize the metal cutting process over the last several decades, much work has concentrated
on the development of mechanistic models to predict cutting forces based upon the method
proposed by Sabberwal. A reasonable amount of success has been achieved by simulating some
machining operations, but the method is process dependent, and material state quantities like
stress, strain, and cutting zone temperature are difficult to obtain [13].
One of the principal challenges associated with the modeling of machining operations is
the complexity associated with the work-tool-chip interaction. The tool chip interface is
characterized by sliding contact between the tool and the workpiece at high normal pressure and
temperature. The energy that is consumed due to friction is mostly converted into heat on the rake
face, causing tool temperatures to be high. In order to counteract this extreme frictional force,
cutting fluids have been used as lubricants in some machining operations [14].
Shaw et al. experimentally observed that the cutting fluid does not lubricate at high speeds.
The possible explanations for this behavior included: chips are carrying cutting fluid away too
quickly for it to reach the cutting zone and serve as a fluid-film lubricant and the time is too short
for the fluid to chemically react with metal surfaces to form a solid-film lubricant. Cassin and
Boothroyd also found that no lubrication was evident at high cutting speeds. They suggested that
lubrication occurs at low speeds by diffusion through the workpiece or that the extreme pressure
additives within the fluid react to form a boundary layer of solid-film lubricant [9].
As noted above, while the primary functions of a cutting fluid are considered to be
lubricating and cooling, lubrication is the dominant function for only those machining operations
that employ low cutting speeds, drilling and tapping. It is to be expected that a fluid in these

17. 10
operations would reduce the friction between the chip and the rake face. However, in drilling and
tapping, a significant amount of friction between chip and tool occurs in locations other than
The rake and flank faces. Another source of friction results when the chips attempt to evacuate
through the flutes. The chips rub against the tool and hole wall, and in some cases the chips clog
the flutes, increasing torque and axial force, increasing tool temperature, and occasionally marring
the hole wall surface. In these cases, the presence of a cutting fluid can reduce the friction between
the chips and tool flutes, enabling the smooth evacuation of chips from the hole and avoiding chip
clogging. Of course, the efficacy of the fluid as a lubricant is very dependent on the success
achieved in delivering it to the bottom of the hole. Furthermore, the character of the chips produced
in drilling and tapping play an important role in the chip clogging phenomenon.
In summary, for low cutting speeds such as found in operations like drilling and tapping,
the technical literature indicates that a cutting fluid can provide lubricating effects that serve to
reduce friction levels, and avoid such undesirable phenomena as chip clogging.

18. 11
Chapter three
Delivery methods of cutting fluids
3.5 Flood cooling
The most common method of delivery cutting fluid is flooding, sometimes called flood -
cooling because it is generally used with coolant-type cutting fluids. In flooding, a steady stream
of fluid is directed at the tool–work or tool–chip interface of the machining operation [15].
3.6 Mist application
A second method of cutting fluid delivery is mist application, primarily used for water based
cutting fluids. In this method the fluid is directed at the operation in the form of a high-speed mist
carried by a pressurized air stream. Mist application is generally not as effective as flooding in
cooling the tool. However, because of the high-velocity air stream, mist application may be more
effective in delivering the cutting fluid to areas that are difficult to access by conventional flooding
[16].
3.7 Manual application
Manual application by means of a squirt can or paint brush is sometimes used for applying
lubricants in tapping and other operations in which cutting speeds are low and friction is a problem.
It is generally not preferred by most production machine shops because of its variability in
application.

19. 12
3.8 Cryogenic Cooling
Cryogenic machining is a material removal process where the conventional cutting fluids are
replaced with cryogenics such as liquid nitrogen, solid carbon dioxide. Cryogenic cooling is used
for effective and fast removal of heat generated during cutting operations and is used for almost
all types of materials with properties ranging from ductile to brittle, and metallic to organic etc. It
has been shown that cryogenic cooling methods do provide better surface properties on the work-
piece, extends tool life, reduces heat effects on work-piece, and reduces dimensional deviations on
work-piece. Further it has been shown that cryogenic cooling would increase machinability of hard
to cut material. Health, safety and environmental friendliness of using cryogenics have made it
attractive for the machining industry. Unlike conventional emulsion cutting fluids which are
widely used, cryogenics such as liquid-nitrogen, dry ice. does not create health or environmental
hazards. Unlike the conventional cutting fluids, liquid nitrogen is not re-circulated in the machine
tool system. Liquid nitrogen absorbs heat generated during cutting operation and evaporates as a
gas and is released to the atmosphere as it does not pollute the environment, or be harmful for
people around. There are three basic types of cryogenic cooling methods which are [17].
3.8.1 Cryogenic pre-cooling of the work-piece
In this method, the work-piece is cooled before machining. Most of the adaptations of this
principle use a technique to cool the cutting area just before the cutting tool does the chip
formation. A typical setup is flooding of the cryogenic using a nozzle over the cutting point just
before the tool contacts with the cutting point.
3.8.2 indirect cryogenic cooling
Indirect cryogenic cooling is also known as cryogenic tool back cooling or conductive
remote cooling, where the cooling takes place without any contact of cryogenic with the work-

20. 13
piece or the tool. Cooling is done by heat conduction from the work-piece and the tool to the
cryogenic chamber placed at the tool face or the tool holder.
3.8.3 cryogenic spraying and jet cooling method
This is concerned with removing heat from the cutting point. Especially, it is focused on
cooling the tool-chip interface with cryogens. Liquid nitrogen is injected in the form of a jet over
the cutting area or sprayed into the cutting area using nozzles, and hence the consumption of liquid.
Chapter four

21. 14
Functions and application of Cutting Fluid
The primary function of cutting fluid is temperature control through cooling and lubrication.
Application of cutting fluid also improves the quality of the workpiece by continually removing
metal fines and cuttings from the tool and cutting zone [18].
4.6 function of cutting fluid
Cutting fluids consist of those liquids and gases that are applied to the tool and the material
being machined to facilitate the cutting operation. Vast quantities are used annually to accomplish
a number of objectives.
4.6.1 Lubrication at low cutting speeds
Figure: 4.1 function of cutting fluid

22. 15
At low cutting speeds, cooling is not very important, while lubrication is important to
reduce friction and avoid the formation of built-up-edge. In this case, an oil based fluid must be
used. At high cutting speeds, the conditions are not favorable to fluid penetration, to reach the
interface and work as a lubricant. In these conditions cooling becomes more important and a water
based fluid must be used.
As lubricant, the cutting fluid works to reduce the contact area between chip and tool and
its efficiency depends on the ability of penetrating in the chip-tool interface and to create a thin
layer in the short available time. This layer is created by either chemical reaction or physical
adsorption and must have a shearing resistance lower than the resistance of the material in the
interface. In this way it will also act indirectly as a coolant because it reduces heat generation and
therefore cutting temperature.
The lubrication efficiency will depend on the fluid properties, such as: wettability
characteristics, viscosity and layer resistance. These properties may be obtained with a suitable
mixture of additives.
4.6.2 Cooling at high cutting speeds
As coolers, cutting fluids decrease cutting temperature through the heat dissipation
(cooling) When water based fluids are used cooling is more important than lubrication. It was
experimentally proved Shaw, et al that the cutting fluid efficiency in reducing temperature
decreases with the increase of cutting speed and depth of cut.
The cutting fluid ability of sweeping the chips away from the cutting zone depends on its
viscosity and its volume flow, besides, of course, the kind of machining operation and chip type
formed. In some machining operations such as drilling and sawing, this function is very important,
because it may avoid chip obstruction and, consequently, tool breakage.
In spite of the fact that this classification is an effective indication of the cooling ability of the
fluids, it does not mean that the fluid that has the highest convection coefficient will provide the
lowest temperature in the chip-tool interface.

23. 16
4.7 Applications
When a cutting fluid is applied, it may cause benefits, do not interfere the process or even be
negative to harm the processes, depending on the cutting conditions, workpiece and tool material.
4.7.1 Applications Where Cutting Fluid Offers Benefits
Cutting with low strength tools, like high speed steels, demands the use of cutting fluid.
This is due to the fact that the heat generated during cutting increases a lot the tool temperature,
reducing its mechanical strength and, thus, making easier the occurrence of plastic deformation
and complete failure. In this case, cutting fluids reduce the temperature, not allowing the tool to
lose its strength and making possible the use of relatively high cutting speeds. Drilling, broaching,
milling, threading with high speed steel tools are typical examples of these operations where the
use of cutting fluids is essential.
Another important application of cutting fluid is in operations where low surface roughness
and/or tight dimensional tolerances are required. In these cases, the lubricant guarantees a good
surface finish and the cooling fluid guarantees the tight tolerances, because it avoids thermal
expansion of the workpiece.
When drilling materials that generate discontinuous chips, like grey cast iron, cutting fluid
application becomes fundamental, mainly in deep drilling. In this case, the main cutting fluid
function is to carry the chips away from the cutting zone.
4.7.2 Applications Where Cutting Fluid Does Not Interfere in the Process

24. 17
This is the use of dry cutting when machining aluminum alloy is in drilling operations. In
this case, the chips tend to stick on the tool and make difficult the evacuation of them, what can
cause drill breakage. Therefore, in this case an abundant volume of cutting fluid or even MQF
must be used. In other operations, in general, dry cutting is recommended, unless tight dimensional
tolerances and low surface roughness are required. Due to the high ductility of the material, it tends
to stick on the tool, producing poor surface roughness. They also have high thermal expansion
coefficient, causing obtaining of high tolerances difficult. In these cases application of cutting
fluids acting both as a lubricant and as a coolant will contribute to reduce the inherent problems.
4.7.3 Applications Where Cutting Fluid Is Negative to the Process
Generally, machining with ceramic tools must be performed without fluid, because it may
promote thermal shocks and, eventually, cause tool breakage. Some ceramic tools, mainly those
based on Si3N4 and the "whiskers", because they have higher toughness and thermal shock
resistance, can avoid this kind of failure and, so, allow some advantages when cutting fluid is
applied.
Other examples of dry machining are interrupted cuttings (like milling) with carbide tools,
where the main kind of wear is cracks of thermal origin that leads to the formation comb of cracks.
In such cases, cracks of thermal origin, transversal to the tool cutting edge appear just after a few
minutes of cut. They are originated by the cyclic variation of the temperature, due to the interrupted
nature of cutting. The cutting edge is heated during the cutting period and cooled during the idle
period. These cracks, as cutting goes on, will increase and propagate, leading to the formation of
comb cracking type of wear.
4.7.4 Application of Minimum Quantity of Fluid (MQF)

25. 18
The choice of a cutting fluid and its method of application depend on important points such
as cost (not just costs of acquisition, but also costs of recycling and maintenance), environmental
effects and influence on human health. These points are becoming more and more important as the
law restrictions on environmental issues become stronger. An alternative for the use of flood of
cutting fluid is the application of a mist of oil or minimum quantity of fluid (MQF), as is being
coined among the scientists. Actually this technique consists of a mixture of drops of cutting fluids
(neat oils or emulsions) in a flow of compressed air, generating a "spray" which is directed to the
cutting region to work as lubricant and coolant.
The MQF technique decreases feed and cutting forces when machining medium carbon steel
with low cutting speeds, mainly for feeds higher than 0.25 mm/rev, In these conditions the values
of forces obtained with the mist system were even lower than those obtained with the application
of an emulsion using conventional method.
4.8 selection of suitable cutting fluids
The selection of cutting fluids in machining processes depends on various factors. The
selection of cutting fluids is carried out according to factors mentioned below:
4.8.1 Type of machining processes
The most important parameter in the selection of cutting fluids is the characteristics of
machining process. Variety of machining processes would indicate relation between workpiece
material-cutting tool-chip combinations. The most difficult machining process will need to use
more cutting fluid. The excellent literature survey in cutting fluids application provided same
important data; machining processes were put in order according to the amount of usable cutting
fluids quantity from the smallest amount to the highest amount.
4.8.2 Workpiece materials

26. 19
The other factor for selection of suitable cutting fluids in machining processes is the type
of workpiece material. The application of cutting fluids should provide easy machining operation
in all materials.
4.8.3 Cutting tool materials
The third influential parameter for selection of cutting fluid in machining processes is the
cutting tool material. Various cutting tool materials are commercially available for all kind of
machining processes. High speed steel cutting tools can be used with all type of cutting fluids.
However waterless cutting fluids are preferred when difficult-to-cut materials are machined.
4.9 Advantages of cutting fluid
a. Increase tool life
b. Lower cutting forces and power required
c. Higher cutting speeds and feeds rates
d. Reduce post-process heat treatments
e. Better workpiece quality
4.10 Disadvantages of cutting fluid
a. Cost related to cutting fluid purchase, storage, maintenance, waste fluid disposal
b. it can cause workpiece and machine tool damages due to a bad maintenance
c. Environmental impact
d. Worker health hazards
Chapter five

27. 20
Environmental effects of cutting fluid
Cutting fluids have a great environmental impact, during all stages of the life cycle. The
main environmental effort is therefore to prolong the life of the fluid. The metalworking fluid's
environmental impact starts when the oil is pumped of the ground. Here is a quick review of the
metalworking fluid's environmental impact, during all steps in the life cycle, from cradle to grave
[19, 20].
5.7 Extraction and manufacturing of components
The first step in cutting fluid's "life" is production of the ingredients that will be mixed
together to produce cutting fluid. These can be fossil oils, or synthetically produced alcohols, fatty
acids, amines, or other chemicals. Here both the amount and choice of material affects the results
that are achieved, but also the energy that is needed to produce different kinds of material. Certain
types of production require more energy, and others are perhaps less resource-efficient in total.
5.8 Manufacturing of concentrate
The production of cutting fluid concentrate has an impact on the environment in several
ways. As with all other production factories in the world much of the production process is
powered by electricity, which can have wide spread of environmental impact depending on energy
source. Furthermore, chemical industries use volatile solvents, classified substances and large
amounts of water in the production. The sum total of the production process' environmental impact
should be reviewed, how much heating or cooling is needed and how effectively the material is
utilized are volatile solvents and expensive metals recycled?
Concentrate producers naturally aim to minimize losses in the production process, as it also
entails a cost. Here, the chemists who formulate the concentrate can also have a major
responsibility in selection of raw materials. The geographic location of the production plant also
has an effect, as the distance and the type of transports affect the final life cycle analysis.

28. 21
5.9 Transportation
The ingredients of the concentrate, the finished formulation and the used cutting fluid must all
be transported at some point during the life cycle, and thus has a negative impact on the climate
and the environment. Important questions to answer are "how", "how far" and "how effective" are
the transports. Air transports have a greater impact on the environment than most other kinds of
transport. A clear improvement within the area of transport is quite simply to reduce use of the
concentrate, since there are then fewer litters that have to be shipped, all the way back to the
number of litters of oil from the oil fields.
5.10 Use and handling
When using of cutting fluid start it naturally has to last for as long as possible, but that also
means that large systems are often constructed to maintain the fluid in good condition. How much
energy is consumed in pumping, heating/cooling, filtering, purifying and maintaining the cutting
fluid in various ways? How much electricity is consumed per litre of fluid in the system? It may
vary between different fluids. Is the service life extended with different kinds of concentrate?
There are many questions to answer when it comes to this aspect, which is easy to disregard. In
many cases, the usage phase in a cutting fluid's life cycle is the one with the largest environmental
impact. The consumption may be high of both energy and new concentrate. Fluid changes, large
amounts of top-up due to fluid being removed in connection with metal chips, or problems with
evaporation mean that the systems consume more concentrate.
5.11 Recycling and reuse
Naturally the environmental impact gets lower when the cutting fluid is reused, since
material consumption decreases. You don't need to purchase new fluid. On the other hand, just as
in the previous stage, the entire picture must be described first. How is the fluid recycled, what is

29. 22
required? Which measures are included when reusing, do you need to pump more fluid, filter more
fluid, add new concentrate and wash old containers? The choice is sometimes made to evaporate
the fluid in order to recover water and reduce the amount of oil and concentrate that has to be
transported for final treatment [21].
5.12 Waste and destruction
When the life cycle is linear, this is the final step in the life cycle. The concentrate is past
its best and is sent for destruction in the form of incineration into carbon dioxide and water. In
theory, some concentrates should be able to biologically degrade and are thus harmless to aquatic
organisms and the environment, and these should not be incinerated. As there unfortunately are
almost always harmful and toxic ingredients in the concentrate, in principal they are always
incinerated. All concentrate must be dealt with as hazardous waste, and must absolutely not be
discharged out into drains or watercourses.

30. 23
Chapter six
Conclusion
Cutting fluids play an important role on machining operations. However, their use have
some drawbacks such as their negative effects over the environment and workers health as by costs
associated such as the equipment, fluids purchase and waste fluid treatment. Conventionally,
mineral oils were used as cutting fluids. However, the mineral oils cooling capacity is limited and
therefore soluble oils were seen as a good alternative. Nevertheless, soluble oils contain water
which is susceptible to bacterial attack. Synthetic lubricants are superior in many regards, but cost
is higher. The alternative techniques such as cryogenic and gaseous cooling fluids have been
implementing in some machining processes, even may become more efficient than conventional
cooling. The best environmental alternative is dry machining since completely removes the cutting
fluid and ensures a clean atmosphere and workers safety, though it has many application
limitations. However, there are still applications where cutting fluids cannot be removed such as
gear making, broaching. It is impossible to carry out the operation with either dry cutting or pure
dry compressed air, because the chip sticks to the spiral channels of the drill, causing its breakage
after few holes. The use of MQF makes the operation feasible and the increase of oil flow in the
mixture does not make the process performance better. The use of cutting fluid generally causes
economy of tools and it becomes easier to keep tight tolerances and to maintain workpiece surface
properties without damages. In the other hand, it brings also some problems, like fluid residuals
and human diseases. Because of them some alternatives has been sought to minimise or even avoid
the use of cutting fluid in machining operations.
The selection of cutting fluids for machining processes generally provides various benefits
such as longer tool life, higher surface finish quality and better dimensional accuracy. These results
also offer higher cutting speeds, feed rates and depths of cut. The productivity of machining
process will be much higher with combination of selecting higher machining parameters. The
material removal rates will be increased. Moreover the application of cutting fluids has negative
effects on health of workers. New approaches for reducing cutting fluids application in machining
processes have been examined and promising results such as dry machining, advancements on

31. 24
cutting tool materials have been reported. Moreover new coating technologies for various cutting
tools have provided important advantages to reduce cutting fluid application in machining
operation. Nevertheless, the machining operations still require the use of cutting fluids in
machining of some materials. Therefore, selection of the most suitable cutting fluid in any
machining process must be carried out to obtain a maximum benefit. The selection of suitable
cutting fluid is affected by mainly three factors in machining operations. These are the types of
machining process, workpiece materials and cutting tool materials. The combination of these three
influential factors would provide basic information for selecting the suitable cutting fluid. The
regeneration methods of used cutting fluids would also provide various advantages such as
reducing cutting the fluids cost, disposals cost of used cutting fluids and nearly eliminating
environmental pollution.

32. 25
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