PERFORMANCE EVALUATION OF CUTTING TOOL
MATERIALS
UNDERSTANDING CHIP FORMATION
Tool geometry
Solid mechanics
Fracture mechanics
 Yielding mechanism
Dislocations etc
TOOL GEOMETRY
FRACTURE MECHANICS
Fracture mechanics is the field of mechanics concerned with the
study of the formation of cracks in materials
It uses the method of analytical solid mechanics to calculate the
driving force on a crack and those of experimental solid mechanics to
characterize the materials resistance to fracture
FRACTURE MECHANICS
ELASTIC BEHAVIOUR
 When a material is being loaded in uni-axial tension,
compression, or simple shear it will behave elastically
until a critical value of normal stress or shear stress is
reached and then it will behave plastically.
 If the applied loads are relatively low, the crystal
responds by simply stretching or compressing the
distance between the atoms. The basic lattice unit does
not change, and all of the atoms remain in their original
position relative to one another.
 Elastic deformation stretches atomic bonds in the
material away from their equilibrium radius of
separation of a bond, without applying enough energy to
break the inter-atomic bonds.
FRACTURE MECHANICS
PLASTIC DEFORMATION
 As the magnitude of applied load is increased, the
distortion increases to a point where the atoms must
either (1) break bonds to produce a fracture, or
(2)slide over one another to produce a permanent
shift of atoms position.
 Plastic deformation is the shearing of atomic planes
over one another to produce a net displacement.
 Plastic deformation tends to occur along planes
having the highest atomic density and greatest
separation.
 Thus plastic deformation occurs by the preferential
sliding of maximum-density planes.
 The specific combination of plane and direction is
called a slip system, and the shear deformation is
known as slip
THEORY OF DISLOCATION
Dislocations are defined
defects
in
a
material's
as line
crystal
structure. They are surrounded by
relatively
strained
(and
weaker)
bonds.
Dislocations are generated and move
when a stress is applied. The motion
of dislocations allows slip – plastic
deformation to occur.
Edge dislocations allow slip to occur
and slip provides ductility in metals.
EDGE DISLOCATION
WORK HARDENING
Work hardening, also known as strain hardening, is the strengthening of a metal by
plastic deformation. This strengthening occurs because of dislocation movements
within the crystal structure of the material.
Increase in the number of dislocations is a quantification of work hardening. Plastic
deformation occurs as a consequence of work being done on a material; energy is
added to the material.
However, ductility of a work-hardened material is decreased. Ductility is the extent
to which a material can undergo plastic deformation, that is, it is how far a material
can be plastically deformed before fracture.
The dislocation density increases due to the formation of new
dislocations and dislocation multiplication. The consequent increasing
overlap between the strain fields of adjacent dislocations gradually
increases the resistance to further dislocation motion. This causes a
hardening of the metal as deformation progresses. This effect is known
as strain hardening(also “work hardening”).
If dislocation motion and plastic deformation have been hindered
enough by dislocation accumulation, and stretching of electronic bonds
and elastic deformation have reached their limit, a third mode of
deformation occurs: fracture
FRACTURE
There are in general two types of
fracture-ductile fracture and brittle
fracture
Ductile
fracture
occurs
after
appreciable plastic strain.
Brittle fracture occurs at a strain that is
below the yield stress.
GRIFFITH’S THEORY
Griffith suggested that the low fracture strength
observed in experiments, as well as the size-dependence of
strength, was due to the presence of microscopic flaws in
the bulk material.
To verify the flaw hypothesis, Griffith introduced an
artificial flaw in his experimental specimens. The artificial
flaw was in the form of a surface crack which was much
larger than other flaws in a specimen.
The experiments showed that the product of the square root of the flaw length
(a) and the stress at fracture (σf) was nearly constant, which is expressed by
the equation:
Griffith developed a thermodynamic approach to explain the relation that
he observed.
The growth of a crack requires the creation of two new surfaces and hence
an increase in the surface energy Griffith found an expression for the
constant C in terms of the surface energy of the crack by solving the
elasticity problem of a finite crack in an elastic plate. Briefly, the approach
was:
 Compute the potential energy stored in a perfect specimen under an
uniaxial tensile load.
 Fix the boundary so that the applied load does no work and then introduce
a crack into the specimen. The crack relaxes the stress and hence reduces
the elastic energy near the crack faces. On the other hand, the crack
increases the total surface energy of the specimen.
 Compute the change in the free energy (surface energy − elastic energy) as
a function of the crack length. Failure occurs when the free energy attains
a peak value at a critical crack length, beyond which the free energy
decreases by increasing the crack length, i.e. by causing fracture. Using this
procedure, Griffith found that
Where E is the Young's modulus of the material and γ is the surface
energy density of the material. Assuming E = 62 GPa and γ = 1 J/m2
gives excellent agreement of Griffith's predicted fracture stress with
experimental results for glass.
OBSERVATIONS
Cutting process generates heat.
Thickness of the chip is greater
than the thickness of the layer from
which it came.
Hardness of the chip is greater than
the hardness of the parent material.
These observations indicate that
the process of chip formation is one
of deformation or plastic flow of the
material.
Plastic flow takes place by means
of a phenomenon called slip along
the slip plane.
As the tool touches the work the
work gets deformed initially the
deformation is elastic in nature.
As the tool gets forward applying
more force the elastic limit is
overcome,
the
flowing plastically.
material
starts
During the plastic deformation, shearing of the atoms take place
this in turn leads to dislocation(edge and screw) to occur in the
material.
This shearing action takes place along the slip plane or the shear
plane.
Due to the dislocation the atoms are separated and reformed and
dislocation increases the ductility of the material.
As a result the material flows plastically up to a point after which
ductility decreases and the material becomes more harder the
process is called as work hardening.
Beyond this point the material becomes brittle and harder and with
the further increase in the load leads to the fracture in the material
During the dislocation taking place the atoms are subjected to severe
tension and compressive
force as a result tensile and compressive
strain field is created which eventually increases the hardness of the
material .
As the metal approaches the shear plane , it does not deform until the
shear plane is reached. It then undergoes substantial amount of shear
as it crosses a thin primary shear zone.
There is no further plastic flow as the chip proceeds up the face of the
tool.
The small amount of secondary shear along the tool face is generated
as the chip flows over the tool in turn generating the friction.
The back of the chip is rough due to the strain being
inhomogeneous. This is due to the presence of points of weakness or
stress concentration present in the metal being cut.
The shear plane passing through a point of stress concentration
will deform at a lower value of stress than one that does not include
a point of stress concentration.
Thus some material in the chips strains more than the other metal
resulting in wavy surface on the back of the chip.
THE CARD MODEL
This model assumes the material cut as a deck of cards.
Exaggerates the in homogeneity of strain.
Assumes shear to occur on a perfectly plane surface.
Ignores any built up edge that may be present.
Involves an arbitrarily assumed shear angle.
This model says that;
All atomic planes are not active shear planes, but only those associated with a
structural defect (second phase particle, missing atom, an impurity, a grain
boundary, etc).
This results in in homogenous strain and a series of sharp points on both surfaces of
the chip.
The points on the free surface remain and serve as an indication of the degree of in
homogeneity pertaining.
Those on the tool face side are removed by
burnishing.
If the structural defects are widely spaced, the free
surface of the chip will have a saw-toothed
appearance.
For less intense and less widely spaced defects, the
free surface of the chip will be relatively smooth.
The teeth will not extend continuously across the
chip but will be localized and staggered.
CHIP FORMATION ANALYSIS
The friction between the tool and the
work material plays an important role in
metal cutting, this friction can be reduced
by
Improved tool finish and sharpness of
the cutting edge.
Use of low-friction work or tool
materials.
Decreased cutting speed (v)
Increased rake angle.
.Use of a cutting fluid.
When the friction reduces there is a corresponding increase in the
shear angle accompanying the decrease in the thickness of the chip.
The plastic strain in the chip decreases with the increases in the
shear angle.
The length of the shear plane significantly decreases with the
increase in the shear angle.
Therefore the force along the shear plane decreases with the
decrease in the shear area.
The temperature of a cutting tool may reach a high value
particularly when a heavy cut is taken at a high speed.
MECHANICS IN METAL CUTTING
The force acting on a cutting tool during the process of metal cutting are the
fundamental importance in the design of cutting tools. The determination of cutting
forces necessary for deformation the work material at the shear zone is essential for
several important requirements:
To estimate the power requirements of a machine tool.
To estimate the straining actions that must be resisted by the
machine tool components, bearings, jigs and fixtures.
To evaluate the role of various parameters in cutting forces.
To evaluate the performance of any new work material, tool
material, environment, techniques etc,with respect to machinability
(cutting forces).
FORCES ACTING ON THE CHIP
When the chip is isolated as a free body, we need to consider only two
forces-the force between the tool face and the chip (R) and the force between
the work piece and the chip along the shear plane (R’). For equilibrium
these must be equal.
R=R’
The forces R and R’ are conveniently resolved into three sets of components
as indicated in figure.
along and perpendicular to the shear plane, Fs and Fn.
along and perpendicular to the tool face, F and N.
in the horizontal and perpendicular to the tool face, Fc and Ft.
MERCHANT CIRCLE ANALYSIS
If the forces R and R’ are plotted at the tool point instead of at their actual
points of application along the shear plane and tool face, we obtain a convenient and
compact diagram. This type of plot was suggested by merchant (1945) and the
corresponding diagram is called as the merchant circle diagram which is as shown
Energy
dissipated
Shearing
Temperature
rise
Heat
Tool
Machine
Tool
Machining
process
Work
part
Problem
The main sources of heat in metal cutting are shown in the Figure. These three distinct
heat sources are:
the shear zone (q1), where the main plastic deformation takes place
the chip-tool interface zone (q2), where secondary plastic deformation due to friction
between the heated chip and the tool takes place
the work tool interface (q3), at flanks where frictional rubbing occurs.
The power consumed in metal cutting is largely converted into heat near
the cutting edge of the tool, and many of the economic and technical
problems of machining are caused directly or indirectly by this heating
action.
The cost of machining is very strongly dependent on the rate of metal
removal, and costs may be reduced by increasing the cutting speed and the
feed rate.
Machining is inherently characterized by generation of heat and high
cutting temperature. At such elevated temperature the cutting tool if not
enough hot hard may lose their form stability quickly or wear out rapidly
resulting in increased cutting forces, dimensional inaccuracy of the product
and shorter tool life.
The magnitude of this cutting temperature increases, though in different degree, with
the increase of cutting velocity, feed and depth of cut, as a result, high production
machining is constrained by rise in temperature. This problem increases further with
the increase in strength and hardness of the work material. Knowledge of the cutting
temperature rise in cutting is important, because increases in temperature:
Following are the observations depicted from the above figure
Maximum temperature is about halfway up the face of the tool
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.
Work part
• Dimensional change
• Thermal damage
Machine Tool
• Distortion
Tool
•
•
•
•
Loss of strength
Decrease hardness
Increased wear rate
Thermal damage
ADVERSE EFFECTS DUE TO TEMPERATURE RISE
Adversely affect the strength, hardness and wear
resistance of the cutting tool
Cause dimensional changes in the part being machined,
making control of dimensional accuracy difficult
Can induce thermal damage to the machined surface,
adversely affecting its properties and service life.
The heat balance in chip formation can be written as:
Total amount of heat generated = (Amount of heat away in
chips ) + (Amount of heat remaining in the cutting tool )+
(Amount of heat passing into the work piece )+ (Amount
of heat radiated into the surrounding).
when a material is deformed elastically, the energy required for the operation
is stored in the material as strain energy, and no heat is generated. However,
when a material is deformed plastically, most of the energy used is converted
into heat. In metal cutting the material is subjected to extremely high strains,
and the elastic deformation forms a very small proportion of the total
deformation; therefore it may be assumed that all the energy is converted into
heat.
Various studies have been made of temperatures in cutting, based on heat transfer and
dimensional analysis, using experimental data. A simple and approximate expression for the
mean temperature for orthogonal cutting is
K = thermal diffusivity (ratio of thermal conductivity to volumetric specific
heat) of the
Work piece material (m2/sec).
pC = volumetric specific heat of the work piece (J/mm2-C)
t = depth of cut (mm)
V = cutting velocity (m/sec) c
U = specific energy in the operation (N-m/mm3)
T = mean temperature rise at the tool-chip interface (oC).
DEFINITION
The change of shape of the tool from its original shape, during cutting,
resulting from the gradual loss of tool material .
OBJECTIVES
Study the general characteristics of tool wear
Understand the causes of tool wear and their consequences
Set up the tool failure criteria and understand the meaning of tool-life
Cutting tools are subjected to an extremely severe rubbing process.
They are in metal-to-metal contact between the chip and work piece,
under conditions of very high stress at high temperature. The situation is
further aggravated (worsened) due to the existence of extreme stress and
temperature gradients near the surface of the tool.
During machining, cutting tools remove material from the component
to achieve the required shape, dimension and surface roughness (finish).
However, wear occurs during the cutting action, and it will ultimately
result in the failure of the cutting tool. When the tool wear reaches a
certain extent, the tool or active edge has to be replaced to guarantee the
desired cutting action.
TOOL WEAR PHENOMENA
The high contact stress between the tool rake-face and the chip causes
severe friction at the rake face, as well, there is friction between the flank
and the machined surface. The result is a variety of wear patterns and
scars which can be observed at the rake face and the flank face
CRATER WEAR
FLANK WEAR
NOTCH WEAR
CHIPPING
ULTIMATE FRACTURE.
Crater wear: The chip flows across the rake face, resulting in severe friction between
the chip and rake face, and leaves a scar on the rake face which usually parallels to
the major cutting edge. The crater wear can increase the working rake angle and
reduce the cutting force, but it will also weaken the strength of the cutting edge. The
parameters used to measure the crater wear can be seen in the diagram. The crater
depth KT is the most commonly used parameter in evaluating the rake face wear.
FLANK WEAR CLEARANCE SURFACE
Wear on the flank (relief) face is called Flank wear and results in the formation of a
wear land. Wear land formation is not always uniform along the major and minor
cutting edges of the tool.
Flank wear most commonly results from abrasive wear of the cutting edge against the
machined surface. Flank wear can be monitored in production by examining the tool or
by tracking the change in size of the tool or machined part. Flank wear can be
measured by using the average and maximum wear land size VB and VBmax.
1. INITIAL (OR PRELIMINARY) WEAR REGION:
Caused by micro-cracking, surface oxidation and carbon loss layer, as well as micro-
roughness at the cutting tool tip in tool grinding (manufacturing). For the new cutting
edge, the small contact area and high contact pressure will result in high wear rate.
The initial wear size is VB=0.05-0.1mm normally.
2 STEADY WEAR REGION
After the initial (or preliminary) wear (cutting edge rounding), the micro-roughness
is improved, in this region the wear size is proportional to the cutting time. The wear
rate is relatively constant.
3 SEVERE (OR ULTIMATE OR CATASTROPHIC) WEAR:
When the wear size increases to a critical value, the surface roughness of the
machined surface decreases, cutting force and temperature increase rapidly, and
the wear rate increases. Then the tool loses its cutting ability. In practice, this region
of wear should be avoided.
Flank wear and chipping will increase the friction, so that the total cutting force
will increase. The component surface roughness will be increased, especially when
chipping occurs. Flank wear will also affect the component dimensional accuracy.
When form tools are used, flank wear will also change the shape of the component
produced.
This is a special type of combined flank and rake face wear which occurs adjacent to the
point where the major cutting edge intersects the work surface.
The gashing (or grooving, gouging) at the outer edge of the wear land is an indication of
a hard or abrasive skin on the work material. Such a skin may develop during the first
machine pass over a forging, casting or hot-rolled work piece. It is also common in
machining of materials with high work-hardening characteristics, including many
stainless steels and heat-resistant nickel or chromium alloys. In this case , the previous
machining operation leaves a thin work-hardened skin.
CHIPPING
Chipping of the tool, as the name implies, involves removal of relatively large discrete particles
of tool material. Tools subjected to discontinuous cutting conditions are particularly prone to
chipping. Chipping of the cutting edge is more like micro-breakages rather than conventional
wear. Built-up edge formation also has a tendency to promote tool chipping. A built-up edge is
never completely stable, but it periodically breaks off. Each time some of the built-up material is
removed it may take with it a lump (piece) of tool edge
ULTIMATE FAILURE
The final result of tool wear is the complete removal of the cutting point - ultimate failure of
the tool. This may come about by temperature rise, which virtually causes the tool tip to soften
until it flows plastically at very low shear stress. This melting process seems to start right at
the cutting edge and because material flow blunts the edge, the melting process continues back
into the tool; within a few seconds a piece of tool almost as large as the engaged depth of cut is
removed.
ABRASIVE WEAR MECHANISM
Abrasive wear is mainly caused by the impurities within the work piece
material, such as carbon, nitride and oxide compounds, as well as the builtup fragments. This is a mechanical wear, and it is the main cause of the tool
wear at low cutting speeds.
ADHESIVE WEAR MECHANISM
The simple mechanism of friction and wear proposed by Bowden and Tabor is based on the
concept of the formation of welded junctions and subsequent destruction of these. Due to the
high pressure and temperature, welding occurs between the fresh surface of the chip and rake
face (chip rubbing on the rake face results in a chemically clean surface). [Process is used to
advantage when Friction Welding to produce twist drills, and broaches, and in tool
manufacturing] Severe wear is characterized by considerable welding and tearing of the softer
rubbing surface at high wear rate, and the formation of relatively large wear particles. Under
mild wear conditions, the surface finish of the sliding surfaces improves
DIFFUSION WEAR MECHANISM
This diffusion results in changes of the tool and work piece chemical composition.
There are several ways in which the wear may be dependent on the diffusion mechanism.
1. Gross softening of the tool
Diffusion of carbon in a relatively deep surface layer of the tool may cause softening and
subsequent plastic flow of the tool.
This flow may produce major changes in the tool geometry, which result in high forces and a
sudden complete failure of the tool.
2. Diffusion of major tool constituents into the work. (chemical element loss)
The tool matrix or a major strengthening constituent may be dissolved into the work and
chip surfaces as they pass the tool. In cast alloy, carbide or ceramic tools, this may be the
prime wear phenomenon. With HSS tools, iron diffusion is possible, but it seems unlikely to
be the predominant wear process. Diamond tool - cutting iron and steel is the typical example
of carbon diffusion.
3. Diffusion of a work-material component into the tool
A constituent of the work material diffusing into the tool may alter the
physical properties of a surface layer of the tool.
For example, the diffusion of lead into the tool may produce a thin
brittle surface layer, this thin layer can be removed by fracture or
chipping.
CONSEQUENCES OF TOOL WEAR
INFLUENCE ON CUTTING FORCES
Crater wear, flank wear (or wear-land formation) and chipping of the cutting edge
affect the performance of the cutting tool in various ways. The cutting forces are
normally increased by wear of the tool. Crater wear may, however, under certain
circumstances, reduce forces by effectively increasing the rake angle of the tool.
Clearance-face (flank or wear-land) wear and chipping almost invariably increase the
cutting forces due to increased rubbing forces.
SURFACE FINISH ( ROUGNESS)
The surface finish produced in a machining operation usually deteriorates as the tool
wears. This is particularly true of a tool worn by chipping and generally the case for a
tool with flank-land wear - although there are circumstances in which a wear land may
burnish (polish) the work piece and produce a good finish.
DIMENSIONAL ACCURACY
Flank wear influences the plan geometry of a tool; this may affect the dimensions of the
component produced in a machine with set cutting tool position or it may influence the
shape of the components produced in an operation utilizing a form tool.
(If tool wear is rapid, cylindrical turning could result in a tapered workpiece)
VIBRATION OR CHATTER
Vibration or chatter is another aspect of the cutting process which may be influenced by
tool wear. A wear land increases the tendency of a tool to dynamic instability. A cutting
operation which is quite free of vibration when the tool is sharp, may be subjected to an
unacceptable chatter mode when the tool wears.
The shop floor has received an order to make 40 components made of
AISI 4140 steel, high speed steel cutting tool is used to produce the
component. A new machinist says that the cutting time can be reduced to
half the time which was before if the tool room would purchase a suitable
tungsten carbide cutter. But the foreman says he does not believe that the
machinists estimate is realistic, and he is not going to spend more money
on the carbide tool. Both of them went to the supervisor of the shop, for a
decision on whether or not to buy the cutter.
Let
Length=600mm
Diameter=150mm.
Labour cost/hr =Rs12/Machine overhead/hr =Rs 400/Grinding cost/hr = Rs 15/Grinding machine overhead cost /hr = Rs 50/Idle time = 5mins
Initial tool cost (hss)= Rs60/Initial tool cost (carbide)= Rs80/-
Tool grinding cost = 5(15+50)/60
Overhead cost Co = 12+40=52/hr =Rs0.8667/min
Tool cost = Ce=60+5.417*9/10=Rs10.875/-
Factors to be considered in the selection of cutting tool material:
•Work material characteristics (chemical and metallurgical state).
•Part characteristics (geometry, accuracy, finish, and surface integrity
requirements)
•Machine tool characteristics, including the work holders (adequate
rigidity with high speed and feed ranges)
•Support systems ( operator’s ability, sensors, controls, method of
lubrication and chip removal)
Required characteristics of a tool material:
•High hardness
•Resistance to abrasion, wear, chipping, of the cutting edge
•High toughness (impact strength)
•High hot hardness
•Strength to resist bulk deformation
•Good chemical stability (inertness or negligible affinity with the work material)
•Adequate thermal properties
•High elastic modulus (stiffness)
•Consistent tool life
•Correct geometry and surface finish
TOOL LIFE EXPECTANCY
The Taylor’s equation for tool life expectancy provides a good
approximation.
VcTn = C
A more general form of the equation is
where
•Vc=cutting speed
•T=tool life
•D=depth of cut
•F=feed rate
•x and y are determined experimentally
n and C are constants found by experimentation or published data;
they are properties of tool material, workpiece and feed rate
From the data hand book
For high speed material and work material –steel 4140,230bhn.
Depth of cut=0.050inches. =1.27mm.
Feed=0.0127inches per revolution
N=0.180
C=190
Cutting speed V=40 m/min=130 ft/min.
Taylor’s tool life equation is given by VcTn = C
logV+nlogT=logC
log130+0.180logT=log190
T=8.234 mins
For carbide material and work material –steel 4140,230bhn.
Depth of cut=0.062inches. =1.574mm.
Feed=0.025inches per revolution
N=0.25
C=475
Cutting speed V=40 m/min=300 ft/min.
Taylor’s tool life equation is given by VcTn = C
logV+nlogT=logC
log300+0.25logT=log475
T=6 mins
ECONOMY
MINIMUM COST CRITERIA HSS MATERIAL
n
Co
n
Optimum cutting speed V=C ----------------------------Ce + TcCo
1- n
V=89.310 m/min
Optimum tool life T =
Tc + Cc /Co
1- n/ n
T=66mins
Machining Time Tm = 3.1428DL/1000fV
Total time =Ti + Tm(Tc/T)
Tt=15.192mins
Cost Of Operation = Co ( Ti ) + Tm (Ce + TcCo )
C=Rs129/-
Tm=9.893mins
MAXIMUM PRODUCTION RATE CRITERION
HSS MATERIAL
Optimum Cutting Speed, V = C (n/TC(1-n))^n
V=127.65m/min
Optimum tool life, T= Tc(1-n)/n
T=9mins
Machining Time Tm = 3.1428DL/1000fV
Tm=6mins
Total time =Ti + Tm(Tc/T)
Tt=12.33mins
Cost Of Operation = Co ( Ti ) + Tm (Ce + TcCo )
C=Rs79.98/-
ECONOMY
MINIMUM COST CRITERIA CARBIDE MATERIAL
n
Co
n
Optimum cutting speed V=C ----------------------------Ce + TcCo
1- n
V=184.80 m/min
Optimum tool life T =
Tc + Cc /Co
1- n/ n
T=43.64mins
Machining Time Tm = 3.1428DL/1000fV
Total time =Ti + Tm(Tc/T)
Tt=9mins
Cost Of Operation = Co ( Ti ) + Tm (Ce + TcCo )
C=Rs29/-
Tm=2mins
MAXIMUM PRODUCTION RATE CRITERION
CARBIDE MATERIAL
Optimum Cutting Speed, V = C (n/TC(1-n))^n
V=303.3m/min
Optimum tool life, T= Tc(1-n)/n
T=6mins
Machining Time Tm = 3.1428DL/1000fV
Tm=1.47mins
Total time =Ti + Tm(Tc/T)
Tt=6.97mins
Cost Of Operation = Co ( Ti ) + Tm (Ce + TcCo )
C=Rs22.96/-
CONCLUSION
On comparison the tool life of the has material is better than the carbide
material.
But the machining time using the carbide material is lesser than using
the hss material.
Cost of the operation is lesser in case of carbide material comparatively.
Hence the shop floor can go with the carbide tool material provided with
good cutting fluid to avoid friction and excess of heat generation and
adverse effects of high cutting speeds