1. Department of Manufacturing Engineering
Cutting Fluids
Prof. Dr. S. Engin KILIÇ
Atılım University
Department of Manufacturing Engineering
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MFGE Chapter 07

2. Cutting fluids-definition
Liquids and gases which are used in metal cutting to improve the cutting performance in comparison to dry cutting are called Cutting Fluids
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3. Advantages of using cutting fluids
Increase in tool life
Improvement of surface finish
Reduction in cutting forces and power consumption
Washing chips free from cutting region
Reduction in thermal distortion of workpiece
Protection of finished surface from corrosion
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4. The Action of cutting fluids
MFGE Chapter 07
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5. The Action of cutting fluids
Cutting fluids affect cutting process through their two
basic actions:
1. Lubrication (reduction in tool friction)
. forms boundary lubrication and a layer of soft chemical
compound with chip and workpiece at very low cutting speeds
a) built-up edge formation is reduced.
b) Reduction in coefficient of friction, hence
increase in shear angle and reduction in cutting forces.
c) Improved surface finish.
d) Increase in tool life.
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6. The Action of cutting fluids
2. Cooling
. reduces temperature in cutting area by removing heat
a) Tool wear is reduced and tool life is increased; tool material
retains its hardness at reduced temperature, hence
. it gains more resistance to abrasion.
. diffusion wear rate is reduced
. due to reduced temperature, however, shear flow
stress may increase, resulting reduced tool life.
b) Reduced thermal expansion and distortion of workpiece
(especially in grinding)
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7. The Action of cutting fluids
3. Swarf removal
An important subsidiary function of a cutting fluid is to wash
away swarf.
. Third-body abrasion is avoided, or at least reduced.
. Surface finish is improved.
MFGE Chapter 07
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8. Basic types of cutting fluids
Straight or neat oils: blended from two types of oils:
Usually undiluted mineral oils: paraffin and other petroleum oils
Often include fats (fattyoils), vegetable oils, esters together with high-pressure compounds based on chlorine, sulphur, phoshorus (high pressure oils)
fatty oils: organic oils of animal or vegetable origin
- Mineral oils
. cheaper
. more stable
- Fatty oils
. have good lubricating properties
. promote good finishes
. less stable than mineral oils and may decompose if used for long periods
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9. Basic types of cutting fluids
- Sulphurised oil-oils with chemically combined sulphur
. prevents pressure welding of chip to tool (B.U.E.)
b) Soluble oils: Cutting fluids which are mainly required to carry away heat and swarf are generally based on water
Oil with emulsifiers to allow oil to disperse in water, to inhibit rusting, to a certain extent for lubricating effect
2-15% in water (e.g % for grinding, 5% for turning and milling)
Least expensive and widely used
Synthetic fluids:
Oil-free solutions formulated from alkaline inorganic and organic compounds with corrosion inhibitors
3-10% in water
Provide best cooling performance
Semi-synthetic fluids:
Combination of synthetic and soluble oil fluids
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10. Basic types of cutting fluids
Straight cutting oils have wide application for two major reasons:
a) Employed in automatic machines because water-base coolants may
find their way into headstock, contaminate lubricating oil and cause
serious deterioration of mechanism.
b) Promote a superior surface finish in gear cutting, honing,
threading and broaching. Paraffin is sometimes used on aluminum
alloys instead of soluble oils because of its wetting property.
Greases are more convenient than oils in tapping and reaming operations
MFGE Chapter 07
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11. Cost of using cutting fluids
Cost of applying cutting fluids:
Reported to constitute 20% of
total manufacturing cost whereas
cutting tool cost is around 7.5%
in European automotive industry
Potential benefits:
in reducing quantities:
dry cutting, near dry cutting
in extending useful life of
cutting fluids:
use of synthetic oils
central recycling systems
Quantities of different types of cutting fluids
(U.S. Manufacturing industry)
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12. Cost of using cutting fluids
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13. General characteristics of water-miscible cutting fluids
After Holmes
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14. General characteristics of water-miscible cutting fluids
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ME Lecture 07

15. Effects of Cutting fluids
Material cut: alloy steel
shear strength = 690 MPa , effective rake 15o
Type of Cutting Fluid
Tool Life(min)
Power (kW)
Dry 12
1.36
Sulphurised oil 27
1.3
Sulphurised and chlorinated oil 33
1.35
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16. Effects of Cutting fluids
Condition
Coefficient of Friction
Heat from friction (kj/kg of metal removed)
Heat from deformation (kj/kg of metal removed)
Dry
1.0
102.3
222.7
Cutting fluid
0.9
93.9
210.4
% decrease 10
19.1
12.8
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17. Guide to the Selection of Cutting Fluids
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18. Cutting Fluids: Pre-conditions for Applicability
It must not be toxic or offensive to the operator;
it should not be a fire hazard;
it must not be harmful to the lubricating system of the machine tool;
it should not corrode or discolor the work material;
it should give some corrosion protection to the freshly cut metal surface;
it should be as cheap as possible.
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19. Application of Cutting Fluids
Cutting fluid should be effectively delivered to the cutting zone to
perform its function
Lubricating fluids must be applied in such a way to form a film on the sliding surfaces
Coolants must gain access to the cutting edge:
flooding cutting area with fluid
continuous application of cutting fluids for intermittent cutting
to avoid micro crack formation in tool material
Fluid application methods:
Manual
Flood
Jet
Mist
Through the tool
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20. Cutting Fluid Applications
Different methods of cooling in milling: (a) compressed air (jet), (b) oil mist,
(c) internal cooling (jet), (d) external cooling (flood)
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21. Flood Application Fluid delivered from a low-pressure
nozzle directed appropriately to
flood tool, workpiece and cutting
zone
Continuous flow to cutting zone,
helps remove chips from cuting zone
Its effectiveness depends on the
geometry of the cutting process
performed
Fluid recollected, filtered and
pumped back to the delivery nozzle
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22. Flood Lubrication in Gear Hobbing
Flood Application
Flood Lubrication in Gear Hobbing

23. Jet Application High-pressure fluid is directed through
a nozzle as high speed jet at cutting zone
Very effective in removing chips from
cutting zone, efficient for high speed
applications including grinding
Fluid recollected, filtered and pumped back to the delivery nozzle
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24. High pressure coolant (HPC) supply system called Jetbreak
Jet Application
Coolant supply at a high pressure up to 1000 bars (i.e., 200 bars is the maximum requirement for titanium machining) shortens the tool/chip contact length and provides improved chip control.
The Jetbreak system, giving a specifically directed nozzle, can be coupled with the appropriate tooling system; hence, coolant supplied through the cone of the coupling into the nozzle jet is directed towards the cutting edge to form a hydraulic wedge between the chip and the rake face of the tool insert.
Most applications are on single spindle turning machines such as vertical turning centres and turn- milling centres.
High pressure coolant (HPC) supply system called Jetbreak
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25. High pressure coolant (HPC) supply system called Hyperson
Jet Application
It provides a high velocity of 122 m/s and a high pressure flow of coolant at 110 bar to the interface between the tool and chip.
System consists of a pumping unit, the piping necessary to transport the fluid, and a tool-holder through which the coolant can pass and which can focus the high pressure flow of coolant on the interface.
High pressure coolant (HPC) supply system called Hyperson
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26. Mist Application
Cutting fluid as an air-carried mist; a mixing system for oil-air pulvarization needed
Usually applicable when cutting speeds are high and uncut chip thickness is relatively small (i.e. end milling)
Good ventillation required due to health hazard
Used in minimum quantity lubrication applications
Minimized lubrication system (mist application)
Small lubrication particles suplied by micro-dosage pump through the capillary tube are mixed with air and directed to the cutting tool through the machine spindle

27. Mist Application Various methods of inducing oil/air mix 4/27/2017
(a) from the outside into the bore
(b) through the cutting tool
(c) oil and air flow entry and exit simultaneously
(d) from a reservoir built into the tool
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28. Cutting fluid requirements for different machining operations
Cutting Fluids
Cutting fluid requirements for different machining operations
4/27/2017
MFGE Chapter 07