2. 1.Properties of tool materials
2.Types of tool materials
HSS
Carbides
Coated carbides
ceramics
3.Cutting fluids, Properties, Types and selcation
4.Heat generation in metal cutting
5.Factors affecting heat generation
6. Heat distribution in tool and work piece and chip
7.Measurement of tool temperature
3. Cutting tool is subjected to:
1. High temperatures,
2. High contact stresses
3. Rubbing along the tool–chip interface and
along the machined surface
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4. 1. Hot hardness
2. Toughness and impact strength
3. Thermal shock resistance
4. Wear resistance
5. Low co efficient frication
6. Cost and easiness in fabrication
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5.
6.
7.
8. Ability of cutting tool to maintain sharp
cutting edge at elevated temp is called as
hot hardness or hot strength.
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12. Tool material must have sufficient toughness to
withstand shocks and vibrations and to prevent
breakage.
ability of the material to absorb energy without failing.
Cutting if often accompanied by impact forces
especially if cutting is interrupted
cutting tool may fail very soon if it is not strong enough
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13. Thermal shock resistance is ability of the tool material
to with failure due sudden changes of working
temperature .
Thermal shock resistance refers to a material's ability to
withstand rapid changes in temperature.
The causes of this sensitivity to thermal shock are the internal
mechanical stresses induced by temperature gradients, and the
highly brittle nature of the ceramic material. Whereas high local
thermal stresses in metals merely lead to a slight local plastic
deformation, they can lead to the propagation of cracks in ceramic
materials. For this reason sudden, large changes of temperature
should be avoided whenever possible.
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14. ◦ The tool material must have withstand excessive
wear even though the relative hardness of the tool
work materials changes
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15. Low co efficient frication at the chips and tool
interface must remain low for minimum wear and
reasonable surface finish
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16. The cost of tool material and easiness of
fabrication should have within reasonable
limits
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17. Tool materials may not have all of the desired properties
for a particular machining operation
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21. High-speed steel (HSS) tools were developed to
machine at low and medium speeds owing to its
superior hot hardness and resistance to wear.
They can be hardened to various depths, have good
wear resistance and are inexpensive
There are two basic types of high-speed steels:
molybdenum (M-series) and tungsten (T-series)
High-speed steel tools are available in wrought, cast
and powder-metallurgy (sintered) forms
They can be coated for improved performance
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22. Typical alloying ingredients:
◦ Tungsten and/or Molybdenum
◦ Chromium and Vanadium
◦ Carbon, of course
◦ Cobalt in some grades
Typical composition:
◦ Grade T1: 18% W, 4% Cr, 1% V, and 0.9% C
ISE 316 - Manufacturing Processes
Engineering
23. Cast-cobalt alloys have high hardness, good wear
resistance and can maintain their hardness at elevated
temperatures
They are not as tough as high-speed steels and are
sensitive to impact forces
Less suitable than high-speed steels for interrupted
cutting operations
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24. Also known as cemented or sintered carbides
They have the following characteristics:
1. High hardness over a wide range of temperatures 1000
degree centigrade
2. High elastic modulus
3. High thermal conductivity
4. Thermal expansion
5. Versatile
6. Cost-effective tool and die materials for a wide range of
applications
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25. Class of hard tool material based on tungsten
carbide (WC) using powder metallurgy
techniques with cobalt (Co) as the binder
Two basic types:
1. Non-steel cutting grades - only WC-Co
2. Steel cutting grades - TiC and TaC added to
WC-Co
ISE 316 - Manufacturing Processes
Engineering
26. High compressive strength but low-to-moderate tensile
strength
High hardness (90 to 95 HRA)
Good hot hardness
Good wear resistance
High thermal conductivity
High elastic modulus - 600 x 103 MPa (90 x 106 lb/in2)
Toughness lower than high speed steel
Lower Thermal shock resistance
It is very brittle
ISE 316 - Manufacturing Processes
Engineering
27. Used for nonferrous metals and gray cast iron
Properties determined by grain size and cobalt
content
◦ As grain size increases, hardness and hot hardness
decrease, but toughness increases
◦ As cobalt content increases, toughness improves at
the expense of hardness and wear resistance
ISE 316 - Manufacturing Processes
Engineering
28. Used for low carbon, stainless, and other alloy
steels For these grades, TiC and/or TaC are
substituted for some of the WC
This composition increases crater wear
resistance for steel cutting, but adversely
affects flank wear resistance for non-steel
cutting applications
ISE 316 - Manufacturing Processes
Engineering
29. Tungsten carbide (WC) consists of tungsten-
carbide particles bonded together in a cobalt
matrix
As the cobalt content increases, the strength,
hardness, and wear resistance of WC decrease
Its toughness increases because of the higher
toughness of cobalt
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30. Consists of a nickel–molybdenum matrix
Has higher wear resistance than tungsten
carbide but is not as tough
Suitable for machining hard materials and for
cutting at speeds higher than tungsten carbide
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31. High-speed steel tools are shaped for applications such
as drill bits and milling and gear cutters
Inserts are individual cutting tools with several cutting
points
Clamping is the preferred method of securing an insert
and insert has indexed (rotated in its holder) to make
another cutting point available
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32. Available in a variety of shapes: square, triangle,
diamond and round
The smaller the included angle, the lower the strength
of the edge
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33. Chip-breaker features on inserts for the purposes of:
1. Controlling chip flow during machining
2. Eliminating long chips
3. Reducing vibration and heat generated
Stiffness of the machine tool is important
Light feeds, low speeds, and chatter are crucial as they
tend to damage the tool’s cutting edge
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34. ISO standards for carbide grades are classified using
the letters P, M, and K
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35. Thin chemically stable shock resistance refractory
coating of TiC,Al2O2 and TiN are applied on the
tungsten carbide inserts.
New alloys and engineered materials are being
developed to have high strength and toughness,
abrasive and chemically reactive with tool materials
properties:
1. Lower friction
2. Higher adhesion
3. Higher resistance to wear and cracking
4. Acting as a diffusion barrier
5. Higher hot hardness and impact resistance
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37. Coatings are applied on cutting tools and inserts by two
techniques:
1. Chemical-vapor deposition (CVD)
2. Physical-vapor deposition (PVD)
Coatings have the following characteristics:
1. High hardness
2. Chemical stability and inertness
3. Low thermal conductivity
4. Compatibility and good bonding
5. Little or no porosity
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38. Titanium-nitride Coatings
Have low friction coefficients, high hardness, resistance
to high temperature and good adhesion to the substrate
Improve the life of high-speed steel tools and improve
the lives of carbide tools, drill bits, and cutters
Perform well at higher cutting speeds and feeds
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39. Figure 22.7 Schematic illustration of typical wear
patterns of high-speed-steel uncoated and titanium-
nitride coated tools. Note that flank wear is
significantly lower for the coated tool 7/11/2023 10:59 AM
40. Titanium-carbide Coatings
Coatings have high flank-wear resistance in machining
abrasive materials
Ceramic Coatings
Coatings have low thermal conductivity, resistance to
high temperature, flank and crater wear
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41. Multiphase Coatings
Desirable properties of the coatings can be combined
and optimized with the use of multiphase coatings
Coatings also available in alternating multiphase
layers
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42. Figure 22.8 Multiphase coatings on a tungsten-carbide
substrate. Three alternating layers of aluminum oxide are
separated by very thin layers of titanium nitride. Inserts with as
many as thirteen layers of coatings have been made. Coating
thicknesses are typically in the range of 2 to 10 μm.
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43. Titanium carbonitride and titanium-aluminum nitride
are effective in cutting stainless steels
Chromium carbide is effective in machining softer
metals that tend to adhere to the cutting tool
More recent developments are nanolayer coatings
and composite coatings
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44. Ions are introduced into the surface of the cutting tool,
improving its surface properties
Process does not change the dimensions of tools
Nitrogen-ion implanted carbide tools have been used
successfully on alloy steels and stainless steels
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45. Ceramic tool materials consist of fine-grained and high-
purity aluminium oxide
Additions of titanium carbide and zirconium oxide
improve toughness and thermal shock resistance
Alumina-based ceramic tools have very high abrasion
resistance and hot hardness
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46. Ceramic cutting tools can he used to machine ‘difficult’
materials at really high cutting speeds sometimes over
2000 m/min. Compare this with the cutting speed for
carbon steel cutting tools — 6 m/min. (4 times of
carbides and 40 times of HSS )
Ceramic cutting tools are very brittle.
They can be used only on machines which are
extremely rigid and free of vibration because low
impact strength
47. Cermets
Consist of ceramic particles in a metallic matrix and
sintered 2200 degree centigrade temp
They are chemical stability and resistance to built-up
edge formation
But they are brittle, expensive and limited usage
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48. Cubic boron nitride is the hardest material available
Carbide provides shock resistance, high wear
resistance and cutting-edge strength
At elevated temperatures, it is chemically inert to iron
and nickel
Its resistance to oxidation is high and suitable for cutting
hardened ferrous and high-temperature alloys
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49. Silicon-nitride (SiN) based ceramic tool materials
consist of silicon nitride with various additions of
aluminum oxide, yttrium oxide and titanium carbide
Tools have high toughness, hot hardness and good
thermal-shock resistance
Due to chemical affinity to iron at elevated temperature,
SiN-based tools are not suitable for machining steels
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50. The hardest substance is diamond
They have low friction, high wear resistance and the
ability to maintain a sharp cutting edge
It is used when a good surface finish and dimensional
accuracy are required
Synthetic or industrial diamonds are used as natural
diamond has flaws and performance can be
unpredictable
As diamond is brittle,
tool shape and sharpness
are important
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51. There is continuous effort of improving the performance
and wear resistance of cutting tools
New tool materials with enhanced properties are:
1. High fracture toughness
2. Resistance to thermal shock
3. Cutting-edge strength
4. Creep resistance
5. Hot hardness
The use of whiskers is for reinforcing fibers in
composite cutting tool materials
Nanomaterials are also becoming important in
advanced cutting-tool materials
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52. Tool costs depend on the tool material, size, shape,
chip-breaker features and quality
The cost of an individual insert is relatively insignificant
Cutting tools can be reconditioned by resharpening
them
Reconditioning of coated tools also is done by recoating
them
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56. Cutting fluids is used to:
1. Reduce friction and wear
2. Cool the tool, work piece (cutting zone
3. Improve the surface finish
4. Reduce forces by decreasing friction tool and work surface
and energy consumption
5. Flush away the chips from the cutting zone
6. Protect the machined surface from environmental corrosion
Depending on the type of machining operation, a coolant, a
lubricant, or both are used
Effectiveness of cutting fluids depends on type of machining
operation, tool and workpiece materials
and cutting speed
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57. Cutting-fluid Action
Cutting fluid seep from the sides of the chip through the
capillary action of the interlocking network of surface
asperities in the interface
Discontinuous cutting operations have more
straightforward mechanisms for lubricant application,
but the tools are more susceptible to thermal shock
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58.
59. • High specific heat and high thermal conductivity
• Good lubricating property
• Non corrosive
• Non toxic and odorless
• High Flash point
• Low viscosity
• Stability -as not to oxide in the air
• Neutral- as not to react chemically
• Odourless
• Harmless
• Non corrosive
• transparency
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60. Effects of Cutting Fluids on Machining
Chain of events taking place after the fluid is shut off:
1. Friction at the tool–chip interface will increase
2. The shear angle will decrease in accordance
3. The shear strain will increase
4. The chip will become thicker
5. A built-up edge is likely to form
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61. Effects of Cutting Fluids on Machining
As a result:
6. The shear energy in the primary zone will increase
7. The frictional energy in the secondary zone will increase
8. The total energy will increase
9. The temperature in the cutting zone will rise
10. Surface finish will to deteriorate and dimensional
tolerances may be difficult to maintain
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62. 62
Heat finds its way into one of three
places
◦ Workpiece, tool and chips
Too much, work
will expand
Too much, cutting edge
will break down rapidly,
reducing tool life
Act as disposable
heat sink
65. 1. Type of operation
2. The rate of metal removal
3. Material of the workpiece
4. Material of the tool
5. Surface finish requirement
6.Cost of cutting fluid
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66. Types of Cutting Fluids
1 water
2.Oils based fluids
-Straight oils
- Soluble oils
3.Mixed oil
4.Synthetics
5.Solid lubricants
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67. Water is very good coolant because it is have
Very heat observing capacity .But plain water is
generally not used because of its tendency to
corrode metal.
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68. Mineral, animal, vegetable, compounded, and
synthetic oils
Low viscosity
They posses very good lubricating property and
heat absorbing characteristics
Protect the finishing surface
Used in light cutting operation
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69. Combination of straight oil and fatty oils
They are having excellent lubricating property
Good accuracy and good surface finish
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70. Oils mixed with chemical additives like
sulphur or chorine have an increased
lubricating and cooling qualities
Tough and very ductile materials
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71. Wax and soap
Non sticking and non flowing
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72. Methods of Cutting-fluid Application
1. Flooding
2. Mist
3. High-pressure systems
4. Through the cutting
tool system
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73.
74. 1 Work piece material and machine tools
2 Biological considerations
3 Environment
Machine-tool operator is in close proximity to cutting
fluids, thus health effects is a primary concern
Progress has been made in ensuring the safe use of
cutting fluids
Recycling involves treatment of the fluids with various
additives, agents, biocides, deodorizers and water
treatment
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75. Near-dry cutting is the application of a fine mist of an
air–fluid mixture containing a very small amount of
cutting fluid
Dry machining is effective on steels, steel alloys, and
cast irons, but not for aluminum alloys
One of the functions of a metal-cutting fluid is to flush
chips from the cutting zone
Cryogenic Machining
Using nitrogen or carbon dioxide as a coolant
The chips are more brittle and machinability is
increased
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76.
77.
78. ISE 316 - Manufacturing
Processes Engineering
Approximately 98% of the energy in machining
is converted into heat
This can cause temperatures to be very high at
the tool-chip
The remaining energy (about 2%) is retained as
elastic energy in the chip
79. 79
Heat finds its way into one of three places
◦ Workpiece, tool and chips
Too much, work
will expand
Too much, cutting edge
will break down rapidly,
reducing tool life
Act as disposable
heat sink
80.
81.
82.
83.
84. ISE 316 - Manufacturing
Processes Engineering
Figure 21.8 - More realistic view of chip formation, showing shear
zone rather than shear plane. Also shown is the secondary shear
zone resulting from tool-chip friction
88. 1.Primary shear zone - Where the major part
of the energy is converted into heat
2. Secondary deformation zone - At the chip –
tool interface where further heat is generated
due to rubbing and / or shear
3.Teratiary deformation zone- At the worn out
flanks due to rubbing between the tool and
the finished surfaces
89. 1 Rapid tool wear, which reduces tool life
2 Plastic deformation of the cutting edge if the
tool material is not enough hot-hard and hot-
strong
3 Thermal flaking and fracturing of thermal
Shocks
4 Built-up-edge formation
90. • Calorimetric method – quite simple and low cost but
inaccurate and gives only grand average value
• Decolourising agent – some paint or tape, which change in
colour with variation of temperature, is pasted on Version
the tool or job near the cutting point; the as such colour of
the chip (steels) may also often indicate cutting
temperature
• Tool-work thermocouple – simple and inexpensive but
gives only
average or maximum value
• Moving thermocouple technique
• Embedded thermocouple technique
• Using compound tool
• Indirectly from Hardness and structural transformation
• Photo-cell technique
• Infra ray detection method
91. ISE 316 - Manufacturing
Processes Engineering
Several analytical methods to calculate cutting
temperature
Method by N. Cook derived from dimensional
analysis using experimental data for various work
materials
where T = temperature rise at tool-chip interface; U = specific energy; v
= cutting speed; to = chip thickness before cut; C = volumetric specific
heat of work material; K = thermal diffusivity of the work material
333
0
4
0
.
.
K
vt
C
U
T o
92. ISE 316 - Manufacturing
Processes Engineering
Experimental methods can be used to
measure temperatures in machining
Most frequently used technique is the
tool-chip thermocouple
Using this method, K. Trigger determined the
speed temperature relationship to be of the
form:
T = K vm
where T = measured tool-chip interface temperature
93. Plastically deform a material using a hard
tool in order to obtain desired physical shape
and properties
Very complex phenomena
Essential for high precision; high
performance products
94. Zone1: Primary zone or shear zone
Zone 2: Secondary zone or tool- chip
interface zone
Zone 3: Tool – work interface zone
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95. 7/11/2023 10:59 AM
There are three main sources of heat when cutting:
1. Heat is produced as the tool deforms (works) the metal
(Primary)
2. Friction on the cutting face (Secondary)
3. Friction on the tool flank (Tertiary)
Heat is mostly dissipated by,
1. The discarded chip carries away heat
2. Coolant will help draw away heat
3. The workpiece acts as a heat sink
4. The cutting tool will also draw away heat.
** factors 1 & 2 dissipate 75 to 80%, factors 3 and 4 dissipate 10%
each
96. FIGURE 8.16 Typical temperature
distribution in the cutting zone.
Note that the maximum
temperature is about halfway up
the face of the tool and that there
is a steep temperature gradient
across the thickness of the chip.
Some chips may become red hot,
causing safety hazards to the
operator and thus necessitating
the use of safety guards. Source:
After G. Vieregge.
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97. Workpiece and tool materials
Cutting variables like speed, feed and depth
of cut
Tool geometry
Cutting fluid
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98. Tool – work thermocouple
Embedded thermocouple
Infrared radiation technique
Thermo-sensitive painting technique
Temper color technique
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102. Selection of cutting tool materials is very
important
What properties should cutting tools have
◦ Hardness at elevated temperatures
◦ Toughness so that impact forces on the tool can be
taken
◦ Wear resistance
◦ Chemical stability
103.
104. o Carbon steel
o High speed steel (HSS)
o Cemented Carbides
o Cast alloys
o Ceramics
o Cubic boron nitride (CBN)
o Diamond
105. Oldest of tool materials
Used for drills taps,broaches ,reamers
Inexpensive ,easily shaped ,sharpened
No sufficient hardness and wear resistance
Limited to low cutting speed operation
106.
107. Retains its hardness at high temperature
Red hardness….
Relatively good wear resistance
108. Composite material consisting of tungsten-carbide particles
bonded together
Alternate name is cemented carbides
Manufactured with powder metallurgy techniques p335 Fig. 2
Small particles are pressed & sintered to desired shape
Amount of cobalt present affects properties of carbide tools
As cobalt content increases – the tougher the tool
114. Commonly known as stellite tools
Composition ranges – 38% - 53 % cobalt
30%- 33% chromium
10%-20%tungsten
Good wear resistance ( higher hardness)
Less tough than high-speed steels and sensitive to impact
forces
Less suitable than high-speed steels for interrupted cutting
operations
Continuous roughing cuts – relatively high g=feeds & speeds
Finishing cuts are at lower feed and depth of cut
115.
116. Individual cutting tool with severed cutting points
Clamped on tool shanks with locking mechanisms
Inserts also brazed to the tools
Clamping is preferred method for securing an insert
Carbide Inserts available in various shapes-Square,
Triangle, Diamond and round
Strength depends on the shape
Inserts honed, chamfered or produced with negative
land to improve edge strength
117. Fig : Methods of
attaching
inserts to
toolholders : (a)
Clamping and
(b) Wing
lockpins. (c)
Examples of
inserts attached
to toolholders
with threadless
lockpins, which
are secured
with side
screws.
118. Used as grinding wheels.
as cutting tool inserts. These are used in a
similar way to cemented carbide inserts.
they can withstand extremely high
machining temperatures.
They also have a high resistance to abrasion.
119. Ceramic cutting tools can he used to machine
‘difficult’ materials at really high cutting
speeds — sometimes over 2000 m/min.
Compare this with the cutting speed for
carbon steel cutting tools — 6 m/min.
Ceramic cutting tools are very brittle.
They can be used only on machines which are
extremely rigid and free of vibration.
120. Made by bonding ( 0.5-1.0 mm ( 0.02-0.04-in)
Layer of poly crystalline cubic boron nitride to a carbide substrate by
sintering under pressure
While carbide provides shock resistance CBN layer provides high
resistance and cutting edge strength
Cubic boron nitride tools are made in small sizes without substrate
Fig : (a) Construction of a polycrystalline cubic boron nitride or a diamond layer on a tungsten-carbide insert. (b)
Inserts with polycrystalline cubic boron nitride tips (top row) and solid polycrystalline CBN inserts (bottom row).
121. Hardest known substance
Low friction, high wear resistance
Ability to maintain sharp cutting edge
Single crystal diamond of various carats used
for special applications
Machining copper—front precision optical
mirrors for ( SDI)
Diamond is brittle , tool shape & sharpened is
important
Low rake angle used for string cutting edge
