Vishveshwarya Technological University

BELAGAVI, KARNATAKA.

A REPORT ON

CUTTING FLUIDS

SHRIKANTH RAMA NAIK 1BI19MSE07

Under the guidance of:

Dr. Chandrashekar A M.tech, PHD
Assistant Professor,
Dept. of Mechanical,
BIT,
Bangalore

Department of Mechanical Engineering

Bangalore Institute of Technology
Bangalore
 ABSTRACT

In this paper, during machining process heat generated and effects tool life shorter,
higher surface roughness and lower the dimensional sensitiveness of work material.
Different methods have been reported to protect cutting tool from the generated heat
during machining operations. The selection of coated cutting tools are an expensive
alternative and generally it is a suitable approach for machining some materials such as
titanium alloys, heat resistance alloys etc. Another alternative is to apply cutting fluids
in machining operation. They are used to provide lubrication and cooling effects
between cutting tool and work piece and cutting tool and chip during machining
operation. Hence the influence of generated heat on cutting tool would be prevented.
The selection of cutting fluids should be carefully carried out to obtain optimum result
in machining processes. The selection criteria of cutting fluids for various material
machining processes have been determined according to cutting tool materials.
Keywords: Machining, Tool materials, Cutting fluids, engineering materials.

i
 CONTENT
Abstract i
List of figure iii

Chapter 1 INTORDUCTION 1
1.1 The desirable properties of cutting fluid in general
Chapter 2 TYPES CUTTING FLUIDS 3
2.1 The following factors should be considered when selecting
A fluid
2.2 Oil-based cutting fluids
2.3 Chemical cutting fluids
Chapter 3 CUTTING FLUID TYPES AND ADVANTAGES VS
DISADVANTAGES 11
3.1.Straight oils
3.2.Soluble oil
3.3.Synthetics
3.4.Semi synthetics
Chapter 4 METHODS OF APPLICATION 13
4.1.Manual application
4.2.Coolant-fed tooling
4.3.Mist applications
4.4.Selection of suitable cutting fluids
Chapter 5 TYPES OF FILTERS 20
5.1.Settling tank system
5.2.Multiple weir system
5.3.Magnetic separators
5.4.Centrifuge separator
5.5.Cyclone separator
Chapter 6 CONCLUSION 24
REFERENCES

ii
 LIST OF FIGURES

Fig Name Page no

Fig 4.1. Cutting Fluid Application, (left) rake face flooding by

Means of Re-circulation 13
Fig 4.2. Internal cutting fluid application in deep hole drilling 14
Fig 4.3. Shows the schematic representation of the experimental setup 14
Fig 5.1 Settling Tank system 20
Fig 5.2 Multiple Weir system 21
Fig 5.5 Cyclone Separator 23

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 Cutting fluids

CHAPTER 1
INTORDUCTION

During machining process, friction between work piece-cutting tool and cutting
tool- chip interfaces cause high temperature on cutting tool. The effect of this generated
heat decreases tool life, increases surface roughness and decreases the dimensional
sensitiveness of work material. This case is more important when machining of
difficult-to- cut materials, when more heat would be observed. Various methods have
been reported to protect cutting tool from the generated heat. Choosing coated cutting
tools are an expensive alternative and generally it is a suitable approach for machining
some materials such as titanium alloys, heat resistance alloys etc.

During metal cutting heat generated as a result of work done .Heat is carried
away from the tool and work by means of cutting fluids, which at the same time reduced
the friction between the tool and chip and between tool and work and facilitates the chip
formation. Cutting fluids usually in the form of a liquid are to the formation zone to
improve the cutting condition. The application of cutting fluids is another alternative to
obtain higher material removal rates. Cutting fluids have been used widespread in all
machining processes. However, because of their damaging influences on the
environment, their applications have been limited in machining processes.

Cost effectiveness of all machining processes has been eagerly investigated.

This is mainly affected selection of suitable machining parameters like cutting speed,
feed rate and depth of cut according to cutting tool and work piece material. The
selection of optimum machining parameters will result in longer tool life, better surface
finish and higher material removal rate.

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.

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 Cutting fluids

1.1. Functions of cutting fluids

 To prevent the tool from overheating i.e. So that no temperature is reached
where the
 Tool’s hardness and resistance to abrasion are reduced, thus decreasing the tool
life.
 To keep the work cool, preventing machining those results in inaccurate final
dimensions.
 To reduce power consumption, wear on the tool, and the generation of heat by
 Affecting the cutting process. This investigation wishes to establish a
relationship
 Between the surface chemistry of the lubricants involved and how they can
accomplish reducing the contact length on the rake face of the tool where most
of the heat during cutting is produced.
 To provide a good surface finish on the work.
 To aid in providing a satisfactory chip formation (related to contact length)
 To wash away the chips/clear the swarf from the cutting area.
 To prevent the corrosion of the work, the tool and the machine.
1.2. The desirable properties of cutting fluid in general
 High thermal conductivity for cooling.
 Good lubricating qualities.
 High flash point should not entail a fire hazard.
 Must not produce a gummy or solid precipitate at ordinary working
temperatures.
 Be stable against oxidation.
 Must not promote corrosion or dislocation of the work material.
 Must afford some corrosion protection to newly formed surfaces.
 The components of the lubricant must not become rancid easily.
 No unpleasant odour must develop from continued use.
 Must not cause skin irritation or contamination.
 A viscosity that will permit free flow from the work and dripping from the chips.

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CHAPTER 2
TYPES CUTTING FLUIDS
The cutting fluids applied in machining processes basically have three characteristics.
These are:
 Cooling effect
 Lubrication effect
Taking away formed chip from the cutting zone. The cooling effect of cutting fluids is
the most important parameter. It is necessary to decrease the effects of temperature on
cutting tool and machined work piece. Therefore, a longer tool life will be obtained due
to less tool wear and the dimensional accuracy of machined work piece will be
improved. The lubrication effect will cause easy chip flow on the rake face of cutting
tool because of low friction coefficient. This would also result in the increased by the
chips. Moreover, the influence of lubrication would cause less built-up edge when
machining some materials such as aluminium and its alloys. As a result, better surface
roughness would be observed by using cutting fluids in machining processes.
It is also necessary to take the formed chip away quickly from cutting tool and machined
work piece surface. Hence the effect of the formed chip on the machined surface would
be eliminated causing poor surface finish. Moreover part of the generated heat will be
taken away by transferring formed chip.
2.1 THE FOLLOWING FACTORS SHOULD BE CONSIDERED
WHEN SELECTING A FLUID:
 Cost and life expectancy
 Fluid compatibility with work materials and machine components
 Speed, feed and depth of the cutting operation
 Type, hardness and microstructure of the metal being machined
 Ease of fluid maintenance and quality control
 Ability to separate fluid from the work and cuttings
 The product’s applicable temperature operating range
 Optimal concentration and pH ranges
 Storage practices
 Ease of fluid recycling or disposal

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 Cutting fluids

The most common metalworking fluids used today belong to one of two categories
based on their oil content:
1. Oil-Based Fluids - including straight oils, soluble oils and ag-based oils
2. Chemical Fluids - including synthetics and semi synthetics
Fluids vary in suitability for metalworking operations. For example, petroleum-based
cutting oils are frequently used for drilling and tapping operations due to their excellent
lubricity while water-miscible fluids provide the cooling properties required for most
turning and grinding operations. The following provides a description of the
advantages, disadvantages and applications of each metalworking fluid category.

2.2 OIL-BASED CUTTING FLUIDS

2.2.1 STRAIGHT OILS (100% petroleum oil)

Straight oils, so called because they do not contain water, are basically
petroleum, mineral, or ag-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) and extreme
pressure (EP) additives such as sulphur, chlorine, or phosphorus compounds. These
additives improve the oil’s wettability; that is, the ability of the oil to coat the cutting
tool, work piece 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.

Advantages:

 The major advantage of straight oils is the excellent lubricity or “cushioning”

effect they provide between the work piece and cutting tool. This is particularly
useful for low speed, low clearance operations requiring high quality surface
finishes.
 Although their cost is high, they provide the longest tool life for a number of
applications.

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 Highly compounded straight oils are still preferred for severe cutting operations
such as crush grinding, severe broaching and tapping, deep-hole drilling, and
for the more difficult to-cut metals such as certain stainless steels and super
alloys.
 They are also the fluid of choice for most honing operations due to their high
lubricating qualities.
 Straight oils offer good rust protection, extended sump life, easy maintenance,
and are less likely to cause problems if misused. They also resist rancidity, since
bacteria cannot thrive unless water contaminates the oil.

Disadvantages

 Straight oils include poor heat dissipating properties and increased fire risk.
 They may also create a mist or smoke those results in an unsafe work
environment for the machine operator, particularly when machines have
inadequate shielding or when shops have poor ventilation systems.
 Straight oils are usually limited to low temperature, low-speed operations.
 The oily film left on the work piece makes cleaning more difficult, often
requiring the use of cleaning solvents.
 Straight oil products of different viscosities are available for each duty class.
Viscosity can be thought of as a lubricant factor--the higher the oil’s viscosity,
the greater its lubricity.
 Highly viscous fluids tend to cling to the work piece and tool. This causes
increased cutting fluid loss by drag out and necessitates lengthier, more costly
clean-up procedures.
 It can be more efficient to choose low-viscosity oil that has been compounded
to provide the same lubricity as a highly viscous one.

2.2.2 SOLUBLE OILS (60-90% petroleum oil)

Soluble oils (also referred to as emulsions, emulsifiable oils 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

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forming a stable “oil-in-water” emulsion. They also cause the oils to cling to the work
piece during machining. Emulsifier particles refract light, giving the fluid a milky,
opaque appearance.

Advantages

 Soluble oils offer improved cooling capabilities and good lubrication due to the
blending of oil and water.
 They also tend to leave a protective oil film on moving components of machine
tools and resist emulsification of greases and slide way oils.
 Soluble oils are a general purpose product suitable for light and medium duty
operations
 Involving a variety of ferrous and nonferrous applications.
 Although they do not match the lubricity offered by straight oils, wetting agents
and EP additives (such as chlorine, phosphorus or sulphur compounds) can
extend their machining application range to include heavy-duty operations.
 Most cutting operations handled by straight oils (such as broaching, trepanning,
and tapping) may be accomplished using heavy-duty soluble oils.

Disadvantages

 The presence of water makes soluble oils more susceptible to rust control
Problems, bacterial growth and rancidity, tramp oil contamination, and
evaporation losses.
 Soluble oils are usually formulated with additives to provide additional
corrosion protection and resistance to microbial degradation.
 Maintenance costs to retain the desired characteristics of soluble oil are
relatively high.
Other disadvantages of soluble oils include the following:
 When mixed with hard water, soluble oils tend to form precipitates on parts,
machines and filters
 Due to their high oil content, they may be the most difficult of the water-
miscible fluids to clean from the work piece. As a result of these disadvantages,
soluble oils have been replaced in most operations with chemical cutting fluids.

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 Cutting fluids

 Misting of soluble oils may produce a dirty and unsafe work environment,
through slippery surfaces and inhalation hazards.

2.3 CHEMICAL CUTTING FLUIDS

Chemical cutting fluids, called synthetic or semisynthetic fluids, are stable,

preformed Emulsions which contain very little oil and mix easily with water. Chemical
cutting fluids rely on chemical agents for lubrication and friction reduction [32].These
additives also improve wettability. At temperatures above approximately 390oF
(200oC), these additives become ineffective and EP lubricant additives (chlorine,
phosphorus and sulphur compounds) are utilized. These compounds react with freshly-
machined metal to form chemical layers which act as a solid lubricant and guard against
welding during heavy-duty machining operations. Fluids containing EP lubricants
significantly reduce the heat generated during cutting and grinding operations.

2.3.1 SYNTHETICS (0% petroleum oil)

Synthetic fluids contain no petroleum or mineral oil. Generally consist of chemical

lubricants and rust inhibitors dissolved in water. Like soluble oils, synthetics are
provided as a concentrate which is mixed with water to form the metalworking fluid.
These fluids are designed for high cooling capacity, lubricity, corrosion prevention, and
easy maintenance. Due to their higher cooling capacity, synthetics tend to be preferred
for high-heat, high velocity turning operations such as surface grinding. They are also
desirable when clarity or low foam characteristics are required. Heavy-duty synthetics,
introduced during the last few years, are now capable of handling most machining
operations. Synthetic fluids can be further classified as simple, complex or emulsifiable
synthetics based on their composition. Simple synthetic concentrates (also referred to
as true solutions) are primarily used for light duty grinding operations. Complex
synthetics contain synthetic lubricants and may be used for moderate to heavy duty
machining operations. Machining may also be performed at higher speeds and feeds
when using complex synthetics. Both simple and complex synthetics form transparent
solutions when mixed in a coolant sump, allowing machine operators to see the work
piece. Emulsifiable synthetics contain additional compounds to create lubrication
properties similar to soluble oils, allowing these fluids to double as a lubricant and
coolant during heavy-duty machining applications. Due to their wettability, good

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cooling and lubricity, emulsifiable synthetics are capable of handling heavy-duty

grinding and cutting operations on tough, difficult-to-machine and high temperature
alloys. The appearance of emulsifiable synthetic fluids ranges from translucent to
opaque. Chemical agents found in most synthetic fluids include:
 Amines and nitrites for rust prevention
 Nitrates for nitrite stabilization
 Phosphates and borates for water softening
 Soaps and wetting agents for lubrication
 Phosphorus, chlorine, and sulphur compounds for chemical lubrication
 Glycols to act as blending agents
 Biocides to control bacterial growth

Advantages:

 Synthetic fluids have the following qualities which contribute to superior

service life
 Excellent microbial control and resistance to rancidity for long periods of time.
 Non-flammable, non-smoking and relatively nontoxic.
 Good corrosion control.
 Superior cooling qualities.
 Greater stability when mixed with hard water.
 Reduced misting problems
 Reduced foaming problems.

Synthetics are easily separated from the work piece and chips, allowing for easy
cleaning and handling of these materials. In addition, since the amount of fluid clinging
to the work piece and chips is reduced, less makeup fluid is needed to replace coolant
lost to drag-out. Good settling properties allow fine particulates to readily drop out of
suspension, preventing them from recirculating and clogging the machine-cooling
system. Overall, synthetics are easier to maintain due to their cleanliness, they offer
long service life if properly maintained and can be used for a variety of machining
operations.

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Disadvantages

 Although synthetics are less susceptible to problems associated with oil-based

fluids, moderate to high agitation conditions may still cause them to foam or
generate fine mists.
 A number of health and safety concerns, such as misting and dermatitis, also
exist with the use of synthetics in the shop.
 Ingredients added to enhance the lubricity and wettability of emulsifiable
synthetics may increase the tendency of these fluids to emulsify tramp oil, foam
and leave semi-crystalline to gummy residues on machine systems (particularly
when mixed with hard water).
 Synthetic fluids are easily contaminated by other machine fluids such as
lubricating oils and need to be monitored and maintained to be used effectively.

2.3.2 SEMISYNTHETICS (2-30% petroleum oil)

As the name implies, semi synthetics (also referred to as semi-chemical fluids) are
essentially a hybrid of soluble oils and synthetics. They contain small dispersions of
mineral oil, typically 2 to 30 percent, in a water-dilatable concentrate. The remaining
portion of a semi-synthetic concentrate consists mainly of emulsifiers and water.
Wetting agents, corrosion inhibitors and biocide additives are also present. Semi
synthetics are often referred to as chemical emulsions or preformed chemical emulsions
since the concentrate already contains water and the emulsification of oil and water
occurs during its production.
The high emulsifier content of semi synthetics tends to keep suspended oil globules
small in size, decreasing the amount of light refracted by the fluid. Semi synthetics are
normally translucent but can vary from almost transparent (having only a slight haze)
to opaque. Most semi synthetics are also heat sensitive. Oil molecules in semi synthetics
tend to gather around the cutting tool and provide more lubricity. As the solution cools,
the molecules redispose.

Advantages

 Like synthetics, semi synthetics are suitable for use in a wide range of
machining applications and are substantially easier to maintain than soluble oils.

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 Cutting fluids

 They provide good lubricity for moderate to heavy duty applications. They also
have better cooling and wetting properties than soluble oils, allowing users to
cut at higher speeds and faster feed rates.
 Their viscosity is also less than that of soluble oil, providing better settling and
cleaning properties.
 semi synthetics provide better control over rancidity and bacterial growth,
generate less smoke and oil mist (because they contain less oil than straight or
soluble oils), have greater longevity, and good corrosion protection.

Disadvantages

 Water hardness affects the stability of semi synthetics and may result in the
formation of hard water deposits.
 Semi synthetics also foam easily because of their cleaning additives and
generally offer less lubrication than soluble oils.

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 Cutting fluids

CHAPTER 3

CUTTING FLUID TYPES AND ADVANTAGES VS

DISADVANTAGES

3.1.STRAIGHT OILS

Advantages Disadvantages
Excellent lubricity Poor heat dissipation
Good rust protection increased risk of fire
Good sump life smoking and misting
Easy Maintenance oily film on work piece
Rancid resistant limited to low-speed severe cutting
operations

3.2.SOLUBLE OIL

Advantages Disadvantages
Good lubrication More susceptible to rust problems
improved cooling capabilities bacterial growth
good rust protection tramp oil contamination and evaporation
losses
general purpose product for light to increased maintenance costs May form
heavy duty operations precipitates on machine

3.3.SYNTHETICS

Advantages Disadvantages
Excellent microbial control and may cause misting
resistance to rancidity
relatively nontoxic foaming and dermatitis
non-flammable/non-smoking may Emulsify tramp oil
good corrosion control easily contaminated by other machine
fluids
superior cooling qualities may form residues

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reduced misting/foaming
easily separated from work piece/chips
good settling/cleaning properties
long service life

3.4. SEMI SYNTHETICS

Advantages Disadvantages
Good microbial control and resistance to Water hardness affects stability
rancidity
relatively nontoxic may cause misting, foaming and
dermatitis
good cooling and lubrication may emulsify tramp oil
easily separated from work piece/chips may form residues
reduced misting/foaming easily contaminated by other machine
fluids
good settling/cleaning properties

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CHAPTER 4
METHODS OF APPLICATION

4.1.MANUAL APPLICATION

Application of a fluid from a can manually by the operator. It is not acceptable even in
job shop situations except for tapping and some other operations where cutting speeds
are very low and friction is a problem. In this case, cutting fluids are used as lubricants.

4.1.1. Flooding

In flooding, a steady stream of fluid is directed at the chip or tool-work piece interface.
Most machine tools are equipped with a recirculating system that incorporates filters
for cleaning of cutting fluids. Cutting fluids are applied to the chip although better
cooling is obtained by applying it to the flank face under pressure:

Fig 4.1. Cutting Fluid Application,(left) rake face flooding by means of re-circulation

4.2.COOLANT-FED TOOLING

Some tools, especially drills for deep drilling, are provided with axial holes through the
body of the tool so that the cutting fluid can be pumped directly to the tool cutting edge.

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Fig 4.2. Internal cutting fluid application in deep hole drilling

4.3.MIST APPLICATIONS

Fluid droplets suspended in air provide effective cooling by evaporation of the fluid.
Mist application in general is not as effective as flooding, but can deliver cutting fluid
to inaccessible areas that cannot be reached by conventional flooding. Mist application
Requires a high pressure and impinged at high speed through the nozzle at the cutting
zone. The mist application system has three components, these are
1. Compressor
2. Mist generator
3. Nozzle

Fig 4.3. Shows the schematic representation of the experimental setup

The compressor used in this system acts as air supply unit and the main purpose is to
supply air at a pressure, which is used in different components of the mist application
system. Mist application system consists of two components (i) fluid chamber and (ii)
nozzle. The fluid chamber has an inlet port and an outlet port at the top and the bottom
respectively. It is used only to contain the cutting fluid. It is connected to the compressor

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by a flexible pipe through the inlet port to keep the fluid inside the chamber under the
constant pressure. It is required to maintain the flow into the nozzle over a long period
of time during machining operation. The fluid chamber has been designed with larger
capacity so as to able to supply fluid continuously during machining. In the inlet section
of nozzle there are two inlet ports through which air and fluid can enter. High pressure
air from the compressor enters into the nozzle mixes with the fluid which come from
the fluid chamber with high pressure. In mist application system a compressor is used
to supply air at high pressure. The cutting fluid which is to be used is placed in the mist
generator, and there is a connection of high pressure air line from the compressor with
the help of flexible pipe at the bottom of the mist generator. When the air at high
pressure enters the mist generator it carries a certain amount of cutting fluid along with
it, and this cutting fluid coming out from the nozzle with the air coming in another from
the compressor as a jet, which is applied to the hot zone. In the mist generator there is
a regulating valve by which the flow rate of the cutting fluid can be controlled. The
photographic and schematic views of the experimental setup are shown in
Fig.3 respectively. During the experiment the thin but high velocity stream of mist is to
be projected along the work tool interfaces as parallel as possible.

4.4.SELECTION OF SUITABLE CUTTING FLUIDS

 Type of machining processes
 Type of machined work piece material
 Type of cutting tool material

4.4.1. 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
Work piece material-cutting tool-chip combinations. The most difficult machining
process will need to use more cutting fluid. Machining processes were put in order
according to the amount of usable cutting fluids quantity from the smallest amount to
the highest amount:
 Grinding
 Cutting with saw
 Turning

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 Planning and shaping

 Milling
 Drilling
 Reaming
 Threading (using high cutting speed and low feed rate)
 Threading operation with shape tools
 Boring
 Drilling deep holes
 Gear production
 Screwing with thread
 Screwing with tap
 Outer broaching
 Inner broaching
The study concluded that this arrangement from using less cutting fluids to high would
be a general approach and this would not provide detailed view of the type machining
processes; the machined work piece material and the cutting tool material and cutting
tool geometry parameters could change this arrangement.
The heavy machining processes (for example broaching or screwing with tap) generally
require middle or heavy cutting oils. Heavy cutting oils or the oils whose chemical
components heavier active oils must be used in the horizontal broaching of steel. More
oils have showed better performance in broaching operations compared to water based
cutting fluids and their chemical components helped to make machining operation
easier. Emulsions and solutions can be used in vertical surface broaching operation;
however the application of oil type cutting fluid would be more suitable. In threading
operation, the interface between cutting tool and work piece is small, but the interface
is continuous. For this operation cooling characteristic of cutting fluid is required.
Drilling process may be more problematic. Cutting speed in drilling operation is
generally low due to two cutting edges of drill tool. Moreover, the geometry of formed
chip is different. Therefore the cooling effect of cutting fluid is more important in
drilling process. In conventional drilling operation, emulsion oils and sulphur or
chlorine additive mineral oils should be selected. These fluids can reduce friction and
as a result less heat generation will be noticed. Using advanced drill tools such as drill
containing holes for cutting fluid application can be preferred.

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4.4.2. TYPE OF MACHINED WORK PIECE MATERIAL

The other factor for selection of suitable cutting fluids in machining processes is the
type of work piece material. The application of cutting fluids should provide easy
machining operation in all materials. The cutting fluid is encountered widespread in
engineering applications will be determined at below.
Cast iron cast group of materials are brittle during machining they break into small size
chips. The friction between cutting tool and chip is less due to small size chip formation.
It was proposed that using emulsion cutting fluids increases surface finish quality and
prevents dust formation during machining. The concentration of emulsion cutting fluid
should be kept around 12% – 15% to decrease oxidation.
In steel machining operation, generally the high pressure containing and additive
cutting fluids are used. In stainless steel machining, high pressure cutting oils should
be selected. Work-hardening properties in some steels would cause some problems
during machining operation. However using sulphur added oils for this kind of steels
machining leave stain over machined surface.
For machining of heat resistant and difficult-to-cut steel alloys, water based cutting
fluids are preferred, because temperature becomes higher in cutting area. The mixture
ration of water based cutting fluids changes between 1/20 – 1/40. In some machining
operations, using sulphur added mineral cutting oils is possible.
During machining of aluminium and aluminium alloys, high temperatures do not occur
Waterless cutting fluids prevent the formation of “built up edge”, however this type of
cutting fluids must be non-active (leaving no stain).
Machining of copper and copper alloys poses similar problems. The application of
emulsion cutting fluids or thin mineral oils should be selected for copper and copper
based alloys machining. High pressure additive cutting oils are preferred for brass
machining. In the machining of nickel and nickel alloys, the machining operation
should be carried out as dry or using cutting fluids. Higher cutting speeds and feed rates
should be selected when cutting fluids are used in the machining of these materials.
Generally sulphured mineral oil as cutting fluid is preferred. Water based cutting fluids
are used in turning with high cutting speed, milling and drilling operations.
The applications of synthetic cutting fluids are possible in drilling and broaching
operations.

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 In machining of the difficult-to-cut materials such as titanium alloys, high

temperature becomes an influential factor for selection of cutting fluid.
Therefore the application of cutting fluid would eliminate the effect of generated
heat during machining process. The selected cutting fluid must have both
cooling and lubricating characteristics.
 The cooling factor of cutting fluid is more important in machining of titanium
alloys due to high heat generation during machining operation. This would also
induce to use higher cutting speeds.
 It is observed that lubrication properties of selected cutting fluids are preferred
when low cutting speeds are selected. Emulsion oil can be selected in the
machining of titanium alloys when cutting speeds are used; chlorine additive
cutting oils are preferred when high cutting speed are selected.
 In the machining operations of composites that used commonly nowadays,
using cutting fluids is recommended. In particular the using cutting fluid has
positive influence on the surface roughness quality.

4.4.3. TYPE OF 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. In case of the tungsten carbide (WC) cutting tools application,
more cooling characteristics from cutting fluids are required. This is because of high
generated heat in the interface of cutting tool and work piece material. The negative
effect of generated heat during machining with WC cutting tools causes rapid tool wear.
Hence toll life will be shorter and surface finish quality falls. Cubic boron nitrate (CBN)
and polycrystalline diamonds (PCD) cutting tools have been found important place in
machining processes. However, these cutting tools are expensive and they can protect
their characteristics in high temperature machining conditions. They are generally used
in finish machining operation to obtain high dimensional accuracy and excellent surface
finish quality. The application of cutting fluids is not necessary when machining
operations are carried out with these cutting tool materials. Ceramic and diamond
cutting tools can also protect their characteristics at high temperatures. They are

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generally used in finish machining operation. In using ceramic cutting tools, air is
sprayed into the cutting zone. The water based cutting fluids must be used when
diamond type cutting tool materials are used.

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CHAPTER 5
TYPES OF FILTERS
Separators and positive filters are the two basic types of filtration equipment and there
are several variations of each type on the market today.

SEPARATORS

5.1 SETTLING TANK SYSTEM

This is the simplest type of filter system and a modification of the individual machine
sump in which the metalworking fluid mix is pumped into a tank where swarf settles to
the bottom. See Fig 5.1.

Fig 5.1 Settling Tank system

The number of machines on the system and chip size is the criteria to consider in tank
size and its design. In most cases, a drag-out chain is needed to scrape the bottom of the
tank and move the settled swarf up a ramp into a tote bin. Figure 1 the settling tank is
best suited for machining operations where chip size is large. A simple settling tank can
be improved by dividing it into two compartments: a clean side and a dirty side
separated by a weir or metal dam. The metalworking fluid mix is pumped into one
compartment (dirty side) where heavy swarf settles and is removed by a drag-out chain.
The partially "cleaned" fluid mix then flows over the weir to the clean side where a
drag-out chain removes finer particles that settle in this compartment.
Advantages: • Low construction costs • Inexpensive to operate and maintain because
no filter media are required.
Disadvantages: • A large tank, which is needed to insure adequate settling time in high
production operations, occupies costly floor space. • Ineffective in settling small cast,
nodular and gray iron fines, and some graphite particles.

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5.2 MULTIPLE WEIR SYSTEM

The multiple weir, or folded weir as it is sometimes called, is a more sophisticated

version of the simple settling tank. The tank contains a series of troughs or metal tubes,
arranged in parallel. See Fig 5.2.

Fig 5.2 Multiple Weir system

The metalworking fluid mix feeds into the "dirty" compartment where mechanical
devices skim floating fines and free oil from the surface into a tote bin. The
metalworking fluid then flows under a retaining wall, up the other side, and rises at a
low flow rate over the weirs into the discharge troughs. From there, it flows into the
"clean" compartment. This type of system allows a maximum amount of settling time
in a relatively small tank. The weirs moderate surface turbulence (which disrupts
settling) and, because of their parallel arrangement, provide as much as ten times the
overflow area of a single weir. A drag-out chain, below the entire skimmer and weir
area, removes the settled fines. The clean section may also have a drag-out chain to
remove additional fines that settle during system downtime.
Advantages: • Very efficient settling unit. • Generally effective on nodular and cast
iron and any type of machining operation. • Inexpensive to operate and maintain
because it does not require filter media.
Disadvantages: • Weirs provide excellent conditions for mold growth. • A product with
good settling properties is required. • Large in size.

5.3 MAGNETIC SEPARATORS

Magnetic separators remove ferrous swarf (iron particles) from the metalworking fluid
mix by attracting it to the magnetized surface of a rotating drum. The "cleaned" fluid

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returns to the machine, and a scraper blade removes the particles from the drum.
Magnetic separators are used predominantly with individual machines or in
combination with positive filters.
Advantages: • Very little maintenance, low cost, and minimal floor space. • No filter
media are required.
Disadvantages: • Will remove only ferrous or magnetic contaminants.

5.4 CENTRIFUGE SEPARATOR

This type of unit generally is used in conjunction with positive filters to remove
extraneous oil and small fines from metalworking fluids. The fluid mix feeds into a
spherical open-type bowl, which spins at a high rpm. Centrifugal force pushes the swarf
to the outside of the bowl. The clean fluid spills over the top of the bowl and is fed back
to the machine. As sludge builds up in the bowl, the centrifuge automatically ejects it;
if not, the centrifuge must be stopped manually and cleaned or replaced.
Advantages: • Excellent for removal of extraneous oil. • No disposable filter media.
Disadvantages: • A centrifuge may break the emulsion in coarse or weak emulsion
products. • High maintenance time and costs. • Cannot handle a large quantity of fluid
because of the low flow rate

5.5 CYCLONE SEPARATOR

Another type of separator is the cyclone. In this filter system, the metalworking fluid
mix is returned from the machine to a settling tank or reservoir where large swarf or
chips settle to the bottom. The partially cleaned fluid is then pumped to the cone-shaped
cyclone filter unit (see Figure 5.5) where it enters tangentially at the top of the widest
portion of the unit. The fluid spirals downward, and as it accelerates in velocity, the
shape of the cone causes a tremendous increase in radial force (2000 times the force of
gravity). With the increasing force, particles of swarf move downward along the outside
of the unit. At the apex of the cone, the fluid mix starts to move up the center of the
cone, while the swarf is forced out at the bottom through a discharge orifice and into a
settling tank or reservoir. The clean fluid moves up the center to the top of the cone and
is piped from there to the machine. A cyclone filter promotes emulsification in contrast
to a centrifuge, which can cause emulsion breaks. It is ideal for individual machine
applications because of its small size. The larger the capacity of a cyclone, the lower its

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efficiency. Therefore, small units usually are connected in banks for large central
system applications.
Advantages: • Simplicity and ease of operation. • No moving parts - little or no
maintenance. • No disposable media costs.
Disadvantages: • Large particles of swarf or other large contaminants must be removed
to prevent plugging of the cyclone • the apex of the cone must be inspected daily and
kept clean to prevent dirt recirculation. • Does not remove the very small fines, leading
to dirt recirculation and metalworking fluid mix depletion • Can cause foam problems
• High Maintenance time and costs

Fig 5.5 Cyclone Separator

The larger the capacity of a cyclone, the lower its efficiency. Therefore, small units
usually are connected in banks for large central system applications. Advantages: •
Simplicity and ease of operation. • No moving parts - little or no maintenance. • No
disposable media costs. Disadvantages: • Large particles of swarf or other large
contaminants must be removed to prevent plugging of the cyclone • the apex of the cone
must be inspected daily and kept clean to prevent dirt recirculation. • Does not remove
the very small fines, leading to dirt recirculation and metalworking fluid mix depletion
• Can cause foam problems • High Maintenance time and costs

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CHAPTER 6

CONCLUSION

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.
New approaches for reducing cutting fluids application in machining processes have
been examined and promising results such as dry machining, advancements on 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, work piece 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.

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REFERENCES

[1] M.B. Da Silva, J. Wallbank, “Lubrication And Application Method In

Machining,Lubrication and Tribology” 50 (1998) 149-152.
[2] E. Brinksmeier, A. Walter, R. Janssen, P. Diersen, “Aspects Of Cooling
Lubrication Reduction in Machining Advanced Materials”,Proceedings of the
Institution of Mechanical Engineers, Journal of Engineering Manufacture, 1999.
[3] M. Sokovic, K. Mijanovic, “Ecological Aspects Of The Cutting Fluids And Its
Influence On Quantifiable Parameters of the Cutting Processes”, Journal of
Materials Processing Technology 109 (2001) 181-189.
[4] W.J. Bartz, “Ecological and Environmental Aspects of Cutting Fluids”,
Lubrication Engineering 57 (2001) 13-16.
[5] M.A. El Baradie, “Cutting Fluids, Part I: Characterisation” Journal of Materials
Processing Technology 56 (1996) 786-797.
[6] M.A. El Baradie, “Cutting Fluids, Part II: Recycling and Clean Machining”,
Journal of Materials Processing Technology 56 (1996) 798-806.
[7] P.S. Sreejith, B.K.A. Ngoi, “Dry Machining; Machining of the Future”, Journal
of Materials Processing Technology 101 (2000) 287-291.
[8] H. Popke, Th. Emmer, J. Steffenhagen, “Environmentally Clean Metal Cutting
Process- Machining on the Way to Dry Machining”, Proceedings of the
Institution of Mechanical Engineers, (1999) 329-332.
[9] T.F. Glenn, F. van Antwerpen, “Opportunities and Market Trends in
Metalworking Fluids”, Lubrication Engineering 54 (1998) 31-37.
[10] E.P. DeGarmo, J.T. Black, R.A. Kosher, “Materials and Processes in
Manufacturing”,

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