The document discusses the theory of metal cutting. It covers topics such as chip formation, shear plane angle determination using the Merchant model, forces acting on the chip, the Merchant equation, power and energy relationships, and cutting temperature analysis. It provides the theoretical foundation for understanding machining processes and operations.

1. THEORY OF METAL CUTTING
1. Overview of Machining Technology
2. Theory of Chip Formation in Metal Machining
3. Force Relationships and the Merchant Equation
4. Power and Energy Relationships in Machining
5. Cutting Temperature
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1

2. Material Removal Processes
• A family of shaping operations, the common feature of which is
removal of material from a starting work part so the remaining
part has the desired geometry
• Machining – material removal by a sharp cutting tool, e.g., turning,
milling, drilling
• Abrasive processes – material removal by hard, abrasive particles,
e.g., grinding
• Nontraditional processes - various energy forms other than sharp
cutting tool to remove material
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3. The family tree
of material
removal
processes
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3

4. • Cutting action involves shear deformation of work material to form
a chip, and as chip is removed, new surface is exposed: (a) positive
and (b) negative rake tools
Dept of Mechanical Engg, ATMECE, Mysuru
Machining

5. Why Machining is Important
• Variety of work materials can be machined
• Most frequently used to cut metals
• Variety of part shapes and special geometric features
possible:
• Screw threads
• Accurate round holes
• Very straight edges and surfaces
• Good dimensional accuracy and surface finish
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6. Disadvantages of Machining
• Wasteful of material
• Chips generated in machining are wasted material
• At least in the unit operation
• Time consuming
• A machining operation generally takes longer to shape a given
part than alternative shaping processes
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7. Machining in the
Manufacturing Sequence
• Generally performed after other basic manufacturing
processes, such as casting, forging, and bar drawing
• Other processes create the general shape of the starting work part
• Machining provides the final shape, dimensions, finish, and special
geometric details that other processes cannot create
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8. Machining Operations
• Most important machining operations:
• Turning
• Drilling
• Milling
• Other machining operations:
• Shaping and planing
• Broaching
• Sawing
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9. • Single point cutting tool removes material from a rotating
workpiece to form a cylindrical shape
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Turning

10. • Used to create a round hole,
usually by means of a
rotating tool (drill bit) with
two cutting edges
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Drilling
10

11. • Rotating multiple-cutting-edge tool is moved across work to cut a
plane or straight surface
• Two forms: peripheral milling (left) and face milling
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Milling
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12. Cutting Tool Classification
1. Single-Point Tools
• One dominant cutting edge
• Point is usually rounded to form a nose radius
• Turning uses single point tools
2. Multiple Cutting Edge Tools
• More than one cutting edge
• Motion relative to work achieved by rotating
• Drilling and milling use rotating multiple cutting edge tools
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13. Cutting Tools
• (a) Single-point tool showing rake face, flank, and tool point;
and (b) a helical milling cutter, representative of tools with
multiple cutting edges
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14. Cutting Conditions in
Machining
• Three dimensions of a machining process
• Cutting speed v – primary motion
• Feed f – secondary motion
• Depth of cut d – penetration of tool below original work surface
• For certain operations (e.g., turning), material removal rate
RMR can be computed as
RMR = v f d
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15. Cutting Conditions in Turning
• Speed, feed, and depth of cut in a turning operation
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16. Roughing vs. Finishing Cuts
• In production, several roughing cuts are usually taken on a
part, followed by one or two finishing cuts
• Roughing - removes large amounts of material from starting work
part
• Some material remains for finish cutting
• High feeds and depths, low speeds
• Finishing - completes part geometry
• Final dimensions, tolerances, and finish
• Low feeds and depths, high cutting speeds
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17. Machine Tool
• A power-driven machine that performs a machining operation,
including grinding
• Functions in machining:
• Holds work part
• Positions tool relative to work
• Provides power at speed, feed, and depth that have been set
• The term also applies to machines that perform metal forming
operations
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18. • Simplified 2-D model of machining that describes the mechanics
of machining fairly accurately
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Orthogonal Cutting Model
18

19. Chip Thickness Ratio
where r = chip thickness ratio; to = thickness of the chip prior
to chip formation; and tc = chip thickness after separation
• Chip thickness after cut is always greater than before, so chip
ratio is always less than 1.0
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c
o
t
t
r 
19

20. Determining Shear Plane Angle
• Based on the geometric parameters of the orthogonal model,
the shear plane angle  can be determined as:
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where r = chip ratio, and  = rake angle



sin
cos
tan
r
r


1
20

21. • (a) Chip formation depicted as a series of parallel plates sliding relative
to each other, (b) one of the plates isolated to show shear strain, and (c)
shear strain triangle used to derive strain equation
Dept of Mechanical Engg, ATMECE, Mysuru
Shear Strain in Chip Formation

22. Shear Strain
• Shear strain in machining can be computed from the
following equation, based on the preceding parallel plate
model
 = tan( - ) + cot 
where  = shear strain,  = shear plane angle, and  =
rake angle of cutting tool
Dept of Mechanical Engg, ATMECE, Mysuru

23. Actual Chip Formation
• 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
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24. Four Basic Types of Chip in
Machining
1. Discontinuous chip
2. Continuous chip
3. Continuous chip with Built-up Edge (BUE)
4. Serrated chip
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25. • Brittle work materials
• Low cutting speeds
• Large feed and depth of cut
• High tool-chip friction
Optics and Lasers in Engineering, Volume 49, Issue 2, February
2011, Pages 240–247
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Discontinuous Chip
25

26. • Ductile work materials
• High cutting speeds
• Small feeds and depths
• Sharp cutting edge
• Low tool-chip friction
Journal of Materials Processing Technology, Volume 121, Issues 2–3, 28
February 2002, Pages 363–372
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Continuous Chip
26

27. • Ductile materials
• Low-to-medium cutting speeds
• Tool-chip friction causes portions
of chip to adhere to rake face
• BUE forms, then breaks off,
cyclically
Springerimages.com
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Continuous with BUE
27

28. • Semi-continuous - saw-tooth
appearance
• Cyclical chip forms with
alternating high shear strain then
low shear strain
• Associated with difficult-to-
machine metals at high cutting
speeds
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Serrated Chip
(springerimages.com)
28

29. • (a) Friction force F and Normal force to friction N
• (b) Shear force Fs and Normal force to shear Fn
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Forces Acting on Chip
29

30. Resultant Forces
• Vector addition of F and N = resultant R
• Vector addition of Fs and Fn = resultant R'
• Forces acting on the chip must be in balance:
• R' must be equal in magnitude to R
• R’ must be opposite in direction to R
• R’ must be collinear with R
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31. Coefficient of Friction
• Coefficient of friction between tool and chip
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 Friction angle related to coefficient of friction as
N
F



 tan

31

32. Shear Stress
• Shear stress acting along the shear plane
where As = area of the shear plane
• Shear stress  = shear strength S of work material during
cutting
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s
s
F
A
 

sin
w
t
A o
s 
32

33. • F, N, Fs, and Fn cannot
be directly measured
• Forces acting on the
tool that can be
measured: Cutting
force Fc and Thrust
force Ft
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Cutting Force and Thrust Force
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34. Forces in Metal Cutting
• Equations to relate the forces that cannot be measured to the
forces that can be measured:
F = Fc sin + Ft cos
N = Fc cos - Ft sin
Fs = Fc cos - Ft sin
Fn = Fc sin + Ft cos
• Based on these calculated force, shear stress and coefficient
of friction can be determined
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35. The Merchant Equation
• Of all the possible angles at which shear deformation can occur,
the work material will select a shear plane angle  that
minimizes energy
• Derived by Eugene Merchant
• Based on orthogonal cutting, but validity extends to 3-D
machining
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2
2
45


 


35

36. What the Merchant Equation
Tells Us
• To increase shear plane angle
• Increase the rake angle
• Reduce the friction angle (or reduce the coefficient of friction)
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2
2
45


 


36

37. • Higher shear plane angle means smaller shear plane which means
lower shear force, cutting forces, power, and temperature
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Effect of Higher Shear Plane
Angle
37

38. Power and Energy
Relationships
• A machining operation requires power
• The power to perform machining can be computed from:
Pc = Fc v
where Pc = cutting power; Fc = cutting force; and v = cutting
speed
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39. Power and Energy
Relationships
• In U.S. customary units, power is traditional expressed as
horsepower (dividing ft-lb/min by 33,000)
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where HPc = cutting horsepower, hp
000
33,
v
F
HP c
c 
39

40. Power and Energy
Relationships
• Gross power to operate the machine tool Pg or HPg is given by
or
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where E = mechanical efficiency of machine tool
 Typical E for machine tools  90%
E
P
P c
g 
E
HP
HP c
g 
40

41. Unit Power in Machining
• Useful to convert power into power per unit volume rate of
metal cut
• Called unit power, Pu or unit horsepower, HPu
or
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where RMR = material removal rate
MR
c
U
R
P
P =
MR
c
u
R
HP
HP =
41

42. Specific Energy in Machining
• Unit power is also known as the specific energy U
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where Units for specific energy are typically
N-m/mm3 or J/mm3 (in-lb/in3)
w
vt
v
F
R
P
P
U
o
c
MR
c
u =
=
=
42

43. Cutting Temperature
• 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
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44. Cutting Temperatures are
Important
• High cutting temperatures result in the following:
• Reduce tool life
• Produce hot chips that pose safety hazards to the machine
operator
• Can cause inaccuracies in part dimensions due to thermal
expansion of work material
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45. Cutting Temperature
• Analytical method derived by Nathan Cook from dimensional
analysis using experimental data for various work materials
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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 work material
333
0
4
0
.
.







K
vt
C
U
T o

45

46. Cutting Temperature
• Experimental methods can be used to measure temperatures
in machining
• Most frequently used technique is the tool-chip thermocouple
• Using this method, Ken Trigger determined the
speed-temperature relationship to be of the form:
T = K vm
where T = measured tool-chip interface temperature, and v =
cutting speed
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47. Example 1
In an orthogonal cutting operation, the 0.250 in wide tool has a rake
angle of 5. The lathe is set so the chip thickness before the cut is
0.010 in. After the cut, the deformed chip thickness is measured to be
0.027 in. Calculate (a) the shear plane angle and (b) the shear strain
for the operation.
• Solution: (a) r = to/tc = 0.010/0.027 = 0.3701
•  = tan-1(0.3701 cos 5/(1 - 0.3701 sin 5)) = tan-1(0.3813) = 20.9
• (b) Shear strain  = cot 20.9 + tan (20.9 – 5) = 2.623 + 0.284 = 2.907
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48. Example 2
In a turning operation on stainless steel with hardness = 200 HB, the
cutting speed = 200 m/min, feed = 0.25 mm/rev, and depth of cut = 7.5
mm. How much power will the lathe draw in performing this operation if
its mechanical efficiency = 90%. Use Table 21.2 to obtain the appropriate
specific energy value.
• Solution: From Table 21.2, U = 2.8 N-m/mm3 = 2.8 J/mm3
• RMR = vfd = (200 m/min)(103 mm/m)(0.25 mm)(7.5 mm) = 375,000
mm3/min = 6250 mm3/s
• Pc = (6250 mm3/s)(2.8 J/mm3) = 17,500 J/s = 17,500 W = 17.5 kW
• Accounting for mechanical efficiency, Pg = 17.5/0.90 = 19.44 kW
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49. Example 3
Consider a turning operation performed on steel whose hardness = 225 HB at a speed = 3.0 m/s, feed =
0.25 mm, and depth = 4.0 mm. Using values of thermal properties found in the tables and definitions of
Section 4.1 and the appropriate specific energy value from Table 21.2, compute an estimate of cutting
temperature using the Cook equation. Assume ambient temperature = 20C.
• Solution: From Table 21.2, U = 2.2 N-m/mm3 = 2.2 J/mm3
• From Table 4.1,  = 7.87 g/cm3 = 7.87(10-3) g/mm3
• From Table 4.1, C = 0.11 Cal/g-C. From note “a” at the bottom of the table, 1 cal = 4.186 J.
• Thus, C = 0.11(4.186) = 0.460 J/ g-C
• C = (7.87 g/cm3)(0.46 J/g-C) = 3.62(10-3) J/mm3-C
• From Table 4.2, thermal conductivity k = 0.046 J/s-mm-C
• From Eq. (4.3), thermal diffusivity K = k/C
• K = 0.046 J/s-mm-C /[(7.87 x 10-3 g/mm3)(0.46 J/g-C)] = 12.7 mm2/s
• Using Cook’s equation, to = f = 0.25 mm
• T = (0.4(2.2)/3.62(10-3))[3(103)(0.25)/12.7]0.333 = 0.2428(103)(59.06)0.333
• = 242.8(3.89) = 944.4 C
• Final temperature, taking ambient temperature in account T = 20 + 944 = 964C
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50. Dept of Mechanical Engg 1

51. Cutting tool materials
The selection of cutting tool material and grade is an important factor
to consider when planning a successful metal cutting operation.
A basic knowledge of each cutting tool material and its performance
is therefore important so that the correct selection for each
application can be made. Considerations include the
workpiece material to be machined, the component type and shape,
machining conditions and the level of surface quality required for
each operation.
Dept of Mechanical Engg 2

52. Cutting-Tool Materials
Tool bits generally made of seven
materials
o High-speed steel
o Cast alloys (such as stellite)
o Cemented carbides
o Ceramics
o Cermets
o Cubic Boron Nitride
o Polycrystalline Diamond
Dept of Mechanical Engg 3

53. Cutting Tool Properties
• Hardness
– Cutting tool material must be 1 1/2 times harder than
the material it is being used to machine.
• Capable of maintaining a red hardness during
machining operation
– Red hardness: ability of cutting tool to maintain sharp
cutting edge
– Also referred to as hot hardness or hot strength
Dept of Mechanical Engg 4

54. • Wear Resistance
o Able to maintain sharpened edge throughout the cutting
operation
o Same as abrasive resistance .
• Shock Resistance
o Able to take the cutting loads and forces
• Shape and Configuration
– Must be available for use in different sizes and shapes.
Dept of Mechanical Engg 5

55. the designation of hard
cutting materials
Hard metals:
HW Uncoated hard metal containing primarily tungsten
carbide (WC).
HT Uncoated hard metal, also called cermet , containing
primarily titanium carbides (TIC) or titanium nitrides (TIN) or
both.
HC Hard metals as above, but coated
Dept of Mechanical Engg 6

56. High-Speed Steel
• May contain combinations of tungsten, chromium,
vanadium, molybdenum, cobalt .
• Can take heavy cuts, withstand shock and maintain
sharp cutting edge under red heat
• Generally two types (general purpose)
o Molybdenum-base (Group M)
o Tungsten-base (Group T)
• Cobalt added if more red hardness desired
Dept of Mechanical Engg 7

57. Cast Alloy
• Usually contain 25% to 35% chromium, 4% to 25%
tungsten and 1% to 3% carbon
o Remainder cobalt
• Qualities
o High hardness
o High resistance to wear
o Excellent red-hardness
• Operate 2 ½ times speed of high-speed steel
• Weaker and more brittle than high-speed steel
Dept of Mechanical Engg 8

58. the designation of hard
cutting materials
Ceramics:
CA Oxide ceramics containing primarily aluminium oxide
(Al2O3).
CM Mixed ceramics containing primarily aluminium oxide
(Al2O3) but containing components other than oxides.
CN Nitride ceramics containing primarily silicon nitride
(Si3N4).
CC Ceramics as above, but coated.
Dept of Mechanical Engg 9

59. the designation of hard
cutting materials
Diamond:
DP Polycrystalline diamond*
Boron nitride:
BN Cubic boron nitride*
*(Polycrystalline diamond and cubic boron nitride are
also called superhard cutting materials ).
Dept of Mechanical Engg 10

60. Cutting tool materials have different combinations of
hardness, toughness and wear resistance, and are
divided into numerous grades with specific properties.
Generally , a cutting tool material that is successful in its
application should be:
• Hard, to resist flank wear and deformation
• Tough, to resist bulk breakage
• Non-reactive with the workpiece material
• Chemically stable, to resist oxidation and diffusion
• Resistant to sudden thermal changes.
Dept of Mechanical Engg 11

61. Coated cemented
carbide (HC)
Coated cemented carbide currently represents 80-90% of all
cutting tool inserts.
Its success as a tool material is due to its unique combination
of wear resistance and toughness, and its ability to be formed
in complex shapes.
Coated cemented carbide combines cemented carbide
with a coating. Together they form a grade which is
customized for its application.
Coated cemented carbide grades are the first
choice for a wide variety of tools and
applications.
Dept of Mechanical Engg 12

62. Coating – CVD
Definition and properties:
CVD stands for Chemical Vapor Deposition.
The CVD coating is generated by chemical reactions
at temperatures of 700-1050°C.
CVD coatings have high wear resistance and excellent
adhesion to cemented carbide.
The first CVD coated cemented carbide was the single
layer titanium carbide coating (TiC).
Alumina coatings (Al2O3) and titanium nitride (TiN)
coatings were introduced later. More recently, the modern
titanium carbonitride coatings (MT-Ti(C,N) or MT-TiCN,
also called MT-CVD) were developed to improve grade
properties through their ability to keep the cemented carbide
interface intact.
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63. Modern CVD coatings combine MT-Ti(C,N), Al2O3 and TiN. The
coating properties have been continuously improved for adhesion,
toughness and wear properties through microstructural
optimizations and post-treatments.
MT-Ti(C,N) - Its hardness provides abrasive wear resistance,resulting in
reduced flank wear.
CVD-Al2O3 – Chemically inert with low thermal conductivity , making it
resistant to crater wear. It also acts as a thermal barrier to improve plastic
deformation resistance.
CVD-TiN - Improves wear resistance and is used for wear detection.
Post-treatments - Improve edge toughness in interrupted cuts and reduce
smearing tendencies.
Dept of Mechanical Engg 14

64. Applications
CVD coated grades are the first choice in a wide range of applications
where wear resistance is important.
Such applications are found in general turning and boring of steel, with
crater wear resistance offered by the thick CVD coatings; general turning
of stainless steels and for milling grades in ISO P, ISO M, ISO K.
For drilling, CVD grades are usually used in the peripheral insert.
Dept of Mechanical Engg 15

65. Coating – PVD
Definition and properties
Physical Vapor Deposition (PVD) coatings are formed
at relatively low temperatures (400-600°C).
The process involves the evaporation of a metal which
reacts with, for example, nitrogen to form a hard nitride
coating on the cutting tool surface.
PVD coatings add wear resistance to a grade due to their
hardness. Their compressive stresses also add edge
toughness and comb crack resistance.
Dept of Mechanical Engg 16

66. The main PVD-coating constituents are described below. Modern
coatings are combinations of these constituents in sequenced layers
and/or lamellar coatings. Lamellar coatings have numerous thin
layers,in the nanometer range, which make the coating even harder.
PVD-TiN - Titanium nitride was the first PVD coating. It has all-round
properties and a golden color.
PVD-Ti(C,N) - Titanium carbonitride is harder than TiN and adds flank wear
resistance.
PVD-(Ti,Al)N - Titanium aluminium nitride has high hardness in combination
with oxidation resistance, which improves overall wear resistance.
PVD-oxide - Is used for its chemical inertness and enhanced crater wear
resistance.
Dept of Mechanical Engg 17

67. Applications
PVD coated grades are recommended for tough, yet
sharp, cutting edges, as well as in smearing materials.
Such applications are widespread and include all solid
end mills and drills, and a majority of grades for grooving,
threading and milling. PVD-coated grades are also
extensively used for finishing applications and as the
central insert grade in drilling.
Dept of Mechanical Engg 18

68. Cemented carbide
Definition and properties
Cemented carbide is a powdery metallurgical material; a composite
of tungsten carbide (WC) particles and a binder rich in metallic
cobalt (Co). Cemented carbides for metal cutting applications
consist of more than 80% of hard phase WC. Additional cubic
carbonitrides are other important components, especially in gradient
sintered grades.
The cemented carbide body is formed, either through powder
pressing or injection moulding techniques, into a body, which is
then sintered to full density.
Dept of Mechanical Engg 19

69. WC grain size is one of the most important parameters for adjusting the
hardness/toughness relationship of a grade; the finer grain size means
higher hardness at a given binder phase content.
The amount and composition of the Co-rich binder controls the grade’s toughness
and resistance to plastic deformation. At equal WC grain size, an increased amount
of binder will result in a tougher grade, which is more prone to plastic deformation
wear. A binder content that is too low may result in a brittle material.
Cubic carbonitrides, also referred to as γ-phase, are generally added to increase hot
hardness and to form gradients.
Gradients are used to combine improved plastic deformation resistance with edge
toughness. Cubic carbonitrides concentrated in the cutting edge improve the hot
hardness where it is needed. Beyond the cutting edge, a binder rich in tungsten
carbide structure inhibits cracks and chip hammering fractures.
Dept of Mechanical Engg 20

70. Applications
Medium to coarse WC grain size
Medium to coarse WC grain sizes provide
the cemented carbides with a superior
combination of high hot hardness and
toughness. These are used in combination
with CVD or PVD coatings in grades for all
areas.
Fine or submicron WC grain size Fine or
submicron WC grain sizes are used for sharp
cutting edges with a PVD coating to further
improve the strength of the sharp edge.
They also benefit from a superior resistance
to thermal and mechanical cyclic loads.
Typical applications are solid carbide drills,
solid carbide end mills, parting off and
grooving inserts, milling and grades for
finishing.
Cemented carbide with gradient The
beneficial dual property of gradients is
Dept of Mechanical Engg 21

71. Uncoated Cemented
Carbide (HW)
Definition and properties
Uncoated cemented carbide grades
represent a very small proportion of the
total assortment. These grades are
either straight WC/Co or have a high
volume of cubic carbonitrides.
Applications
Typical applications are machining of
HRSA (heat resistant super alloys) or
titanium alloys and turning hardened
materials at low speed.
The wear rate of uncoated cemented
carbide grades is rapid yet controlled,
with a self-sharpening action.
Dept of Mechanical Engg 22

72. Cermet (CT)
Definition and properties
A cermet is a cemented carbide with titanium
based hard particles. The name cermet
combines the words ceramic and metal.
Originally, cermets were composites
of TiC and nickel. Modern cermets are nickel-
free and have a designed structure of titanium
carbonitride Ti(C,N) core particles, a second
hard phase of (Ti,Nb,W)(C,N) and a W-rich
cobalt binder.
Ti(C,N) adds wear resistance to the grade, the
second hard phase increases the plastic
deformation resistance, and the amount of
cobalt controls the toughness.
In comparison to cemented carbide, cermet
has improved wear resistance and reduced
smearing tendencies. On the other hand, it
Dept of Mechanical Engg 23

73. Applications
Cermet grades are used in smearing applications where built-up
edge is a problem. Its self-sharpening wear pattern keeps cutting
forces low even after long periods in
cut. In finishing operations, this enables a long tool life and close
tolerances, and
results in shiny surfaces.
Typical applications are finishing in stainless steels, nodular cast irons,
low carbon
steels and ferritic steels. Cermets can also be applied for trouble
shooting in all
ferrous materials.
Hints:
• Use low feed and depth of cut.
• Change the insert edge when flank wear reaches 0.3 mm.
• Avoid thermal cracks and fractures by machining without coolant.
Dept of Mechanical Engg 24

74. Ceramic (CA, CM, CN,
CC)
Definition and properties
All ceramic cutting tools have excellent wear resistance at high cutting
speeds.
There are a range of ceramic grades available for a variety of
applications.
Oxide ceramics are aluminium oxide based (Al2O3), with added
zirconia (ZrO2) for crack inhibition. This generates a material that is
chemically very stable, but which lacks thermal shock resistance.
(1) Mixed ceramics are particle reinforced through the addition of
cubic carbides or carbonitrides (TiC, Ti(C,N)). This improves toughness
and thermal conductivity.
Dept of Mechanical Engg 25

75. (2) Whisker-reinforced ceramics use silicon carbide whiskers (SiCw)
to dramatically increase toughness and enable the use of coolant.
Whisker-reinforced ceramics are ideal for machining Ni-based alloys.
(3) Silicon nitride ceramics (Si3N4) represent another group of ceramic
materials. Their elongated crystals form a self-reinforced material with high
toughness. Silicon nitride grades are successful in grey cast iron, but a lack of
chemical stability limits their use in other workpiece materials.
Sialon (SiAlON) grades combine the strength of a self-reinforced silicon
nitride network with enhanced chemical stability. Sialon grades are ideal for
machining heat resistant super alloys (HRSA).
Dept of Mechanical Engg 26

76. CC620 Oxide ceramic for high speed finishing of grey cast iron in stable and
dry conditions.
CC6050 Mixed ceramic for light, continuous finishing in hardened materials.
CC650 Mixed ceramic for high speed finishing of grey cast irons and
hardened materials, and for semi-finishing operations in HRSA with low toughness
demands.
CC670 Whisker ceramic with excellent toughness for turning, grooving and
milling of Ni-based alloys . Can also be used for hard part turning in unfavorable
conditions.
CC6190 Silicon nitride grade for rough to finish turning and high speed dry
milling of cast iron, perlitic nodular
CC6090 cast irons and hardened cast irons.
CC6090 Coated silicon nitride grade for light roughing to finish turning of cast
iron.
GC1690 Sialon grade for optimized performance when turning pre-machined
HRSA in stable conditions.
CC6060 Predictable wear due to good notch wear resistance.
Dept of Mechanical Engg 27

77. Polycrystalline cubic boron
nitride, CBN (BN)
Definition and properties
Polycrystalline cubic boron nitride, CBN, is a
material with excellent hot hardness that
can be used at very high cutting speeds. It
also exhibits good toughness and thermal
shock resistance.
Modern CBN grades are ceramic
composites with a CBN content of 40-65%.
The ceramic binder adds wear resistance to
the CBN, which is otherwise prone to
chemical wear. Another group of grades
are the high content CBN grades, with 85%
to almost 100% CBN. These grades may
have a metallic binder to improve their
toughness.
Dept of Mechanical Engg 28

78. CBN is brazed onto a cemented carbide carrier to form an
insert. The Safe-Lok™ technology further enhances the
bondage of CBN cutting tips on negative inserts.
Applications
CBN grades are largely used for finish turning of hardened
steels, with a hardness over 45 HRc. Above 55 HRc, CBN is the
only cutting tool which can replace traditionally used
grinding methods. Softer steels, below 45 HRc, contain a
higher amount of ferrite, which has a negative effect on the
wear resistance of CBN.
CBN can also be used for high speed roughing of grey cast
irons in both turning and milling operations.
Dept of Mechanical Engg 29

79. CB7015 PVD coated CBN grade with ceramic binder for continuous
turning, and light interrupted cuts in hardened steels.
CB7025 CBN grade with ceramic binder for interrupted cuts and high
toughness demands when turning hardened steels.
CB7050 High content CBN grade with metallic binder for heavy
interrupted cuts in hardened steels and for finishing grey cast iron. PVD
coated .hardness demands when turning hardened steels.
Dept of Mechanical Engg 30

80. Polycrystalline diamond, PCD (DP)
Definition and properties
PCD is a composite of diamond particles sintered
together with a metallic binder. Diamond is the
hardest, and therefore the most abrasion resistant,
of all materials. As a cutting tool, it has good wear
resistance but it lacks chemical stability at high
temperatures and dissolves easily in iron.
CD10
PCD grade for finishing and semi-finishing of non-ferrous and non-metallic
materials in turning and milling.
Dept of Mechanical Engg 31

81. To understand the advantages and limitations of each material, it is
important to have some knowledge of the different wear mechanisms
to which cutting tools are subjected.
Abrasive
Flank wear
The most common type of wear and the preferred wear
type, as it offers predictable and stable tool life. Flank
wear occurs due to abrasion, caused by hard constituents
in the workpiece material.
Dept of Mechanical Engg 32

82. • Chemical Crater wear
Crater wear is localized to the rake side of the insert. It is
due to a chemical reaction between the workpiece material
and the cutting tool and is amplified by cutting speed.
Excessive crater wear weakens the cutting edge and may
lead to fracture.
Adhesive
Built-up edge (BUE)
This wear type is caused by pressure welding of the
chip to the insert. It is most common when machining
sticky materials, such as low carbon steel, stainless
steel and aluminium. Low cutting speed increases the
formation of built-up edge.
Dept of Mechanical Engg 33

83. Adhesive Notch wear
Insert wear characterized by excessive localized
damage on both the rake face and flank of the insert at
the depth of cut line. Caused by adhesion (pressure
welding of chips) and a deformation hardened
surface. A common wear type when machining
stainless steels and HRSA.
Thermal Plastic deformation
Plastic deformation takes place when the tool
material is softened. This occurs when the cutting
temperature is too high for a certain grade. In
general, harder grades and thicker coatings improve
resistance to plastic deformation wear.
Dept of Mechanical Engg 34

84. Thermal
Thermal cracks
When the temperature at the cutting edge changes
rapidly from hot to cold, multiple cracks may appear
perpendicular to the cutting edge. Thermal cracks are
related to interrupted cuts, common in milling
operations, and are aggravated by the use of coolant.
Mechanic
Edge chipping/breakage
Chipping or breakage is the result of an overload of
mechanical tensile stresses. These stresses can be due
to a number of reasons, such as chip hammering, a
depth of cut or feed that is too high, sand inclusions in
the workpiece material, built-up edge, vibrations or
excessive wear on the insert.
Dept of Mechanical Engg 35

85. LATHE OPERATIONS

86. Bonus Quiz 1
• Name the three primary parameters that must
be specified for a machining operation.
• These three parameters allow us to decide if we
have the power to physically perform the
operation. What (three letters) calculation can
we get from the primary parameters to begin to
address the necessary power requirements?
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87. Manufacturing Operations
• Four classes of Processing Operations:
• Solidification Processes
• Particulate Processes
• Deformation Processes
• Material Removal Processes
• Two classes of Assembly Operations:
• Mechanical Assembly
• Joining
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88. Machining
Variety of work materials can
be machined
• Most frequently applied to
metals
Variety of part shapes and
special geometry features
possible, such as:
• Screw threads
• Accurate round holes
• Very straight edges and flat
surfaces
Good dimensional accuracy
and surface finish
Wasteful of material
• Chips generated in machining
are wasted material, at least in
the unit operation
Time consuming
• A machining operation
generally takes more time to
shape a given part than
alternative shaping processes,
such as casting, powder
metallurgy, or forming
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89. Machining Operations
• Generally performed after other manufacturing
processes (casting, forging, …)
• Other processes create the general shape of the workpart
• Machining provides the final shape, dimensions, finish, and
special geometric details that other processes cannot create
• Most important machining operations:
• Turning
• Drilling
• Milling
• Other machining operations:
• Shaping and planing
• Broaching
• Sawing
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90. Primary Machining Parameters
• Cutting Speed – (v)
• Primary motion
• Peripheral speed m/s ft/min
• Feed – (f)
• Secondary motion
• Turning: mm/rev in/rev
• Milling: mm/tooth in/tooth
• Depth of Cut – (d)
• Penetration of tool below original work surface
• Single parameter mm in
• Resulting in Material Removal Rate – (MRR)
MRR = v f d mm3/s in3/min
where v = cutting speed; f = feed; d = depth of cut
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91. Turning Parameters Illustrated
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Figure 22.5 - Turning operation [Groover (2004), p.503]

92. Drilling
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• Creates a round hole in a
workpart
• Contrasts with boring
which can only enlarge an
existing hole
• Cutting tool called a drill
or drill bit
• Customarily performed on
a drill press
Figure 21.3 (b) drilling
[Groover (2004), p.501]

93. Milling Parameters Illustrated
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Figure 21.3 - Two forms of milling:
(a) peripheral milling, and (b) face milling
[Groover (2004), p.516]

94. Machining Operations &
Parameters
Operation Type Speed Feed Depth of Cut
Turning:
workpiece rotates
single point cutting
Surface speed
(periphery) of
workpiece
Parallel to the
workpiece axis*
(*except parting/grooving)
Tool penetration
below original
work surface
Drilling:
tool rotates
single pass cutting
Surface speed
(periphery) of
tool
Parallel to the
tool axis
Tool penetration
below original
work surface
(depth of hole)
Milling:
tool rotates
multi-point cutting
Surface speed
(periphery) of
tool
Perpendicular to
the tool axis
Tool penetration
below original
work surface
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95. Cut Types: Roughing &
Finishing
Cut Type
Number
of
Passes
Speed Feed Depth of Cut
Roughing:
removes large
amounts to get
close to shape
1 + Low High
0.4 - 1.25 mm/
.015 - .050 in/
High
2.5 - 20 mm
.100 - .750 in
Finishing:
achieves final
dimensions,
tolerances, and
finish
1 - 2 High Low
0.125 - 0.4 mm/
.005 - .015 in/
Low
0.75 - 2.0 mm
.030 - .075 in
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96. Turning
• A single point cutting tool removes material from a
rotating workpiece to generate a rotationally
symmetric shape
• Machine tool is called a lathe
• Types of cuts:
• Facing
• Contour turning
• Chamfering
• Parting (Cut-off) / Grooving
• Threading
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97. Turning Parameters Illustrated
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Figure 22.5 - Turning operation [Groover (2004), p.503]

98. Facing
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Figure 22.6 (a) facing
Tool is fed
radially inward

99. Contour Turning
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Instead of feeding the tool
parallel to the axis of
rotation, tool follows a
contour that is not
necessarily straight (thus
creating a contoured
form).
Figure 22.6 (c) contour turning

100. Right & Left Hand Tools
• Right Hand Tool:
• Cuts from right to left
• Left Hand Tool:
• Cuts from left to right
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101. Chamfering
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Cutting edge cuts an angle
on the corner of the
cylinder, forming a
"chamfer"
Figure 22.6 (e) chamfering

102. Parting (Cutoff) / Grooving
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Tool is fed radially into
rotating work at some
location to cut off end of
part, or provide a groove
Figure 22.6 (f) cutoff

103. Threading
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Pointed form tool is fed
linearly across surface of
rotating workpart parallel
to axis of rotation at a large
feed rate, thus creating
threads
Figure 22.6 (g) threading

104. Engine Lathe
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Figure 22.7
Diagram of
an engine
lathe,
showing its
principal
components

105. Chuck
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Figure 22.8 (b) three-jaw chuck

106. Turret Lathe
• Manual operation is replaced by a “turret” that holds
multiple tools
• Tools are rapidly brought into action by indexing the turret
• Tool post is replaced by multi-sided turret to index multiple
tools
• Applications: high production work that requires a sequence
of cuts on the part
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107. CNC Turret Lathe
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Tool Turret
Spindle Speed
Spindle
Cross Slide
+ Z-axis
+ X-axis
Ways

108. CNC Lathe: Air-Operated
Chuck
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Right Hand
Profile Tool
Chuck

109. CNC Lathe: Tool Turret
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Tool Turret
Right Hand
Profile Tool
Left Hand
Profile Tool
Grooving /
Parting Tool
Tool Holder

110. Machining Calculations:
Turning
• Spindle Speed - N (rpm)
• v = cutting speed
• Do = outer diameter
• Feed Rate - fr (mm/min -or- in/min)
• f = feed per rev
• Depth of Cut - d (mm/rev -or- in/rev)
• Do = outer diameter
• Df = final diameter
• Machining Time - Tm (min)
• L = length of cut
• Mat’l Removal Rate - MRR (mm3/min -or- in3/min)
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o
D
π
v
N 
2
f
o D
D
d


r
m
f
L
T 
f
N
fr 
d
f
v
M R R 

111. Questions & Issues
• Finish Machining (Drilling & Milling) Next Week:
• Next Topic: Process Planning
• Following Week: Group Technology
• Lab this week:
• Fixturing (manual tools & drill press)
• Lab next week:
• Manual Lathe & Mill Operations:
• Rough & Finish Profiling Cuts
• Facing Cuts
• Parting Cuts
• Tool Changes
• Touch-Off
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112. Drilling machine

113. Introduction
• Drilling is a metal cutting process carried out by a rotating
cutting tool to make circular holes in solid materials.
• Tool which makes hole is called as drill bit or twist drill.
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114. Drillingmachine
• A power operated machine tool which holds the drill in its
spindle rotating at high speeds and when actuated move
linearly against the work piece produces a hole.
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115. Types of drilling machine.
• Portable drilling machine
• Bench drilling machine
• Radial drilling machine
• Pillar drilling machine
• Gang drilling machine
• Multiple drilling machine
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116. Portable drilling machine
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117. Bench drilling machine
• These are light duty machines used in small workshops.
• Also called Sensitive drilling machines because of its accurate
and well balanced spindle.
• Holes of diameter 1 mm to 15 mm.
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118. Bench drilling machine
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119. parts
• Vertical main column
• Base
• Moving drill head
• Work table
• Electric motor
• Variable speed gear
box and spindle feed
mechanism.
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120. working
• Work piece with the exact location marked on
it with the centre punch is clamped rigidly on
the work table.
• spindle axis and center punch indentation are
in same line.
• Machine is started and drill bit is lowered by
rotating feed handle.
• Drill bit touches the work and starts removing
material.
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121. Bench drilling machine
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122. Radial drilling machine
• These are heavy duty and versatile drilling machine used to
perform drilling operate on large and heavy work piece.
• Holes up to 7.5 cm.
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123. Radial drilling machine
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124. parts
• Heavy base
• Vertical column
• Horizontal arm
• Drilling head
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125. working
• Work piece is marked for exact location and mounted on the
work table.
• Drill bit is then located by moving the radial arm and drill to
the marked location.
• By starting drill spindle motor holes are drilled.
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126. Drilling machine operation
• Reaming
• Boring
• Counter boring
• Counter sinking
• Spot facing
• Tapping
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127. Reaming
• It is a process of smoothing the surface of drilled holes with a
tool.
• Tool is called as reamer.
• Initially a hole is drilled slightly smaller in size.
• Drill is replaced by reamer.
• Speed is reduced to half that of the drilling.
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128. Reaming
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129. Boring
• It is process carried
on a drilling
machine to increase
the size of an
already drilled hole.
• Initially a hole is
drilled to the
nearest size and
using a boring tool
the size of the hole
is increased.
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130. Counter boring
• This process
involves increasing
the size of a hole at
only one end.
• Cutting tool will
have a small
cylindrical portion
called pilot.
• Cutting speed = two-
thirds of the drilling
speed for the same
hole.
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131. Counter sinking
• This is an operation
of making the end of
a hole into a conical
shape.
• Cutting speed = half
of the cutting speed
of drilling for same
hole.
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132. Dept
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133. Spot facing
• It is a finishing
operation to
produce flat round
surface usually
around a drilled
hole, for proper
seating of bolt head
or nut.
• It is done using a
special spot facing
tool.
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134. Dept
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135. Dept
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136. Tapping
• Process of cutting
internal threads
with a thread tool
called as tap.
• Tap is a fluted
threaded tool used
for cutting internal
thread
• Cutting speed is
very slow.
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137. Dept
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138. Specification of a radial drilling
machine
• Power capacity eg:
1.5 hp for drilling
motor and 0.5 hp for
elevating motor.
• The range of speed
of spindle eg: 50 to
2800 rpm.
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139. • Length of arm on
which drill head can
traverse. eg: 600
mm.
• Vertical movement of
the arm eg: 500 mm.
• Angular swing of arm
eg: 360˚
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140. • Range to which drill
bit can reach eg: 350
mm to 900 mm.
• Drill depth eg: 32
mm for steel.
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141. Dept
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142. Machining Processes Used to Produce
Various Shapes: Milling

143. PartsMadewithMachiningProcessesofChapter24
Figure 24.1 Typical parts and shapes that can be produced with the
machining processes described in this chapter.
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144. MillingandMillingMachines
Millingoperations
• Milling: a process in which a rotating multi-tooth cutter
removes material while traveling along various axes with
respect to the workpiece.
• Figure 24.2: basic types of milling cutters & milling
operations
• In peripheral milling (also called plain milling), the axis
of cutter rotation is parallel to the workpiece surface.
When the cutter is longer than the width of the cut, the
process is called slab milling
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145. MillingCuttersandMillingOperations
Figure 24.2 Some basic types of milling cutters and milling operations. (a) Peripheral milling. (b) Face
milling. (c) End milling. (d) Ball-end mill with indexable coated-carbide inserts machining a cavity in a
die block. (e) Milling a sculptured surface with an end mill, using a five-axis numerical control machine.
Source: (d) Courtesy of Iscar. (e) Courtesy of The Ingersoll Milling Machine Co.
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146. MillingOperations
Figure 24.3 (a) Schematic illustration of conventional milling and climb milling. (b) lab-
milling operation showing depth-of-cut, d; feed per tooth, f; chip depth-of-cut, tc; and
workpiece speed, v. (c) Schematic illustration of cutter travel distance, lc, to reach full
depth-of-cut.
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147. MillingandMillingMachines
Millingoperations:Slabmilling
• Conventional Milling (Up Milling)
• Max chip thickness is at the end of the cut
• Advantage: tooth engagement is not a function of
workpiece surface characteristics, and contamination or
scale on the surface does not affect tool life.
• Cutting process is smooth
• Tendency for the tool to chatter
• The workpiece has a tendency to be pulled upward,
necessitating proper clamping.
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148. MillingandMillingMachines
Millingoperations:Slabmilling
• Climb Milling (Down Milling)
• Cutting starts at the surface of the workpiece.
• Downward compression of cutting forces hold workpiece
in place
• Because of the resulting high impact forces when the
teeth engage the workpiece, this operation must have a
rigid setup, and backlash must be eliminated in the table
feed mechanism
• Not suitable for machining workpiece having surface
scale.
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ATMECE,
Mysuru
7

149. MillingandMillingMachines
Millingoperations:Slabmilling
MillingParameters
•
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150. MillingandMillingMachines
Millingoperations:Slabmilling
MillingParameters
• EXAMPLE 24.1 Material-removal Rate, Power, Torque, and
Cutting Time in Slab Milling
• A slab-milling operation is being carried out on a 300-mm-long,
100-mm-wide annealed mild-steel block at a feed f = 0.25
mrn/tooth and a depth of cut d = 3.0 mm. The cutter is D = 50 mm
in diameter, has 20 straight teeth, rotates at N = 100 rpm, and, by
definition, is wider than the block to be machined, Calculate the
material-removal rate, estimate the power and torque required for
this operation, and calculate the cutting time.
• Solution:
From table 21.2 U=3 W.S/mm3
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151. MillingandMillingMachines
Millingoperations:Slabmilling
MillingParameters-Example24.2
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10

152. Face-MillingOperation
Figure 24.4 Face-milling operation showing (a) action of an insert in face
milling; (b) climb milling; (c) conventional milling; (d) dimensions in face milling.
The width of cut, w, is not necessarily the same as the cutter radius.
The cutter is mounted
on a spindle whose axis
of rotation is
perpendicular to wp
surface.
Lc= D/2
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153. Face-MillingCutterwithIndexableInserts
Figure 24.5 A face-milling cutter with indexable inserts. Source:
Courtesy of Ingersoll Cutting Tool Company.
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
12

154. EffectofInsertShape
onFeedMarksona
Face-MilledSurface
Figure 24.6 Schematic illustration of the effect of insert shape on feed marks on a face-
milled surface: (a) small corner radius, (b) corner flat on insert, and (c) wiper, consisting of
small radius followed by a large radius which leaves smoother feed marks. (d) Feed marks
due to various insert shapes.
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Mysuru
13

155. Face-MillingCutter
Figure 24.7 Terminology for a face-milling cutter.
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156. EffectofLeadAngleonUndeformedChipThicknessinFace
Milling
Figure 24.8 The effect of the lead angle on the
undeformed chip thickness in face milling. Note
that as the lead angle increases, the chip
thickness decreases, but the length of contact
(i.e., chip width) increases. The edges of the
insert must be sufficiently large to accommodate
the contact length increase.
Lead angle of insert has a direct
influence on undeformed chip
thickness
As the lead angle increases,
undeformed chip thickness
decreases, length of contact
increases
Range of lead angles = 0-45
X-sectional area of undeformed
chip remains constant
As lead angle decreases, there is
a smaller vertical force comp (axial
force)
Ratio of cutter diameter, D, to
width of cut should be no less than
3:2
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15

157. PositionofCutterandInsertinFaceMilling
Figure 24.9 (a) Relative position of the cutter and insert as it first engages the
workpiece in face milling. (b) Insert positions towards the end of cut. (c) Examples of
exit angles of insert, showing desirable (positive or negative angle) and undesirable
(zero angle) positions. In all figures, the cutter spindle is perpendicular to the page and
rotates clockwise.
EXAMPLE 24.2 Material-removl Rate, Power Required, and
Cutting Time in Face Milling
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16

158. MillingandMillingMachines
Millingoperations:EndMilling
• The cutter usually rotates on an axis perpendicular to
workpiece
• End mills are available with hemispherical ends (bull
nose mills) for the production of sculptured surfaces, such
on dies and molds.
• End milling can produce a variety of surfaces at any
depth, such as curved, stepped, and pocketed.
Dept
of
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17

159. BallNoseEndMills
Figure 24.10 Ball nose end mills.
These cutters are able to produce
elaborate contours and are often
used in the machining of dies and
molds. (See also Fig. 24.2d.)
Source: Courtesy of Dijet, Inc.
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
18

160. Cutters
Figure 24.11 Cutters for (a) straddle milling, (b) form
milling, (c) slotting, and (d) slitting with a milling cutter.
a. Straddle: more cutters are
used to machine two parallel
surfaces on the workpiece
b. Form milling produces
curved profiles using cutters
that have specially shaped
teeth
Slotting and slitting operations
are performed with circular
cutters. [T-slot cutters,
Dept
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19

161. T-SlotCuttingandShellMill
Figure 24.12 (a) T-slot cutting with a milling cutter. (b) A shell mill.
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
20

162. GeneralRecommendationsforMillingOperations
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
21

163. TroubleshootingGuideforMillingOperations
Dept
of
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Engg,
ATMECE,
Mysuru
22

164. MachinedSurfaceFeaturesinFaceMilling
Figure 24.13 Machined surface features in face milling. See also Fig. 24.6.
Dept
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ATMECE,
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23

165. EdgeDefectsinFaceMilling
Figure 24.14 Edge defects in face milling: (a) burr formation along
workpiece edge, (b) breakout along workpiece edge, and (c) how it can be
avoided by increasing the lead angle (see also last row in Table 24.4).
Dept
of
Mechanical
Engg,
ATMECE,
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24

166. MillingandMillingMachine
DesignAndOperatingGuidelines
• Use standard milling cutters as much as possible
• Chamfers should be used instead of radii
• Avoid internal cavities and pockets with sharp corners
• Workpiece should be sufficiently rigid to minimize any
deflections resulting from clamping and cutting forces
Dept
of
Mechanical
Engg,
ATMECE,
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25

167. MillingandMillingMachine
MillingMachines
• The basic components of these machines are as follows:
• Worktable: on which the workpiece is clamped using T-slots. The
table moves longitudinally relative to the saddle.
• Saddle: supports the table and can move in the transverse direction.
• Knee: supports the saddle and gives the table vertical movement so
that thedepth of cut can be adjusted and workpieces with various
heights can be accommodated.
• Overerarm: used on horizontal machines; it is adjustable to
accommodate different arbor lengths.
• Head: contains the spindle and cutter holders. In vertical machines,
the head may be fixed or can be adjusted vertically, and it can be
swiveled in a vertical plane on the column for cutting tapered
surfaces.
Dept
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Mechanical
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ATMECE,
Mysuru
26

168. Column-and-KneeTypeMillingMachines
Figure 24.15 Schematic illustration of (a) a horizontal-spindle column-and-
knee type milling machine and (b) vertical-spindle column-and-knee type
milling machine. Source: After G. Boothroyd.
Dept
of
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Engg,
ATMECE,
Mysuru
27

169. FIGURE 24.16 Schematic illustration of a bed-type milling machine.
Bed-typeMillingMachine
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28

170. CNCVertical-SpindleMillingMachine
Figure 24.16 A computer numerical-control (CNC) vertical-spindle milling machine. This
machine is one of the most versatile machine tools. The original vertical-spindle milling
machine used in job shops is still referred to as a “Bridgeport”, after its manufacturer in
Bridgeport, Connecticut. Source: Courtesy of Bridgeport Machines Dibision, Textron Inc.
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
29

171. Five-AxisProfileMillingMachine
Figure 24.18 Schematic illustration of a five-axis profile milling machine. Note that
there are three principal linear and two angular movements of machine components.
Dept
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30

172. Grinding machines

173. Grinding
• Grinding is a surface finishing operation where very thin layer
of material is removed in the form of dust particles.
• Thickness of material removed is in range of 0.25 to 0.50 mm.
• Tool used is a abrasive wheel.
Dept
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174. Dept
of
Mechanical
Engg,
ATMECe,
Mysuru
3

175. Dept
of
Mechanical
Engg,
ATMECe,
Mysuru
4

176. Abrasives
• Abrasive is the material employed for sharpening, grinding
and polishing operations.
• Natural abrasive – emery, corundum, quartz, sandstone,
diamond, etc.
• Artificial abrasive – carborundum, aloxite, alundum, etc.
Dept
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5

177. Applications of abrasives
 Corundum : is a natural mineral which consists of aluminium
oxide. Hardest natural substance after diamond.
 Used for shaping, finishing and polishing other tools.
 Emery : natural abrasive consisting of aluminium oxide and
little amount of iron oxide.
 Silicon carbide : synthetic abrasive harder than aluminium
oxide.
 Used to grind metals like iron, brass and soft bronze.
 Used in non metals like wood and leather industries.
Dept
of
Mechanical
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ATMECe,
Mysuru
6

178. • Zirconia aluminia : it is a mixture of zirconium oxide and
aluminium oxide.
• Used in casting and foundry industries.
• Cubic boron nitride : is made up of boron nitride with a cubic
crystalline structure.
• Used for hard coating material.
• Diamond :
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179. Bonding materials
• These are adhesives which holds the abrasive grains together.
• Vitrified process :
• Silicate process :
• Elastic process :
• Rubber or vulcanite process :
Dept
of
Mechanical
Engg,
ATMECe,
Mysuru
8

180. Grinding machines
• Grinding machine is a power operated
machine tool where, the work piece is fed
against constantly rotating abrasive wheel
to remove thin layer of material from work.
Dept
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Mechanical
Engg,
ATMECe,
Mysuru
9

181. Principle of grinding machines
• Work piece is fed against the rotating abrasive wheel.
• Due to action of rubbing or friction between the abrasive particles
and work piece material is removed.
Dept
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Mechanical
Engg,
ATMECe,
Mysuru
10

182. Classification of grinding machine
• Bench grinding machine
• Surface grinding machine
• Cylindrical grinding machine
• Center less grinding machine
• Internal grinding machine
• Special purpose grinding machine
Dept
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Mechanical
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ATMECe,
Mysuru
11

183. Surface grinding machine
• It is machine basically used to grind flat surface.
• Job is mounted to a table which moves longitudinally as well
as in transverse direction.
• Manual feed or power feed.
• Work piece can clamped in two ways
• Manual clamps.
• Magnetic chuck.
Dept
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ATMECe,
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12

184. • Internal pump and piping arrangement for coolant.
• Protective guard for safety.
Dept
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ATMECe,
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13

185. • Base
• Column
• Table traverse
and vertical feed
hand wheel.
• Wheel guard and
protective guard.
Dept
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ATMECe,
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14

186. • Working
• Work piece is clamped to the table by operating magnetic chuck.
• Required grade of grinding tool is fixed to spindle.
• Grinding operation is carried out be operating both table traverse
wheel and vertical feed hand wheel.
Dept
of
Mechanical
Engg,
ATMECe,
Mysuru
15

187. Cylindrical grinding machine
• It is a process of grinding curved surfaces.
• Surface may be straight or tapered.
• Work piece is mounted on two centers, one is tailstock centre
and the other is headstock centre.
• Head stock center may or may not revolve.
Dept
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ATMECe,
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16

188. Working principle
Dept
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ATMECe,
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17

189. Dept
of
Mechanical
Engg,
ATMECe,
Mysuru
18

190. Centre less grinding machine
• It is used to grind curved surface work piece which are long
and slender.
• Work piece rests on a work-rest blade and is backed by a
second wheel called as regulating wheel.
• Grinding wheel pushes the work piece down the work-rest
blade against the regulating wheel.
Dept
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191. Dept
of
Mechanical
Engg,
ATMECe,
Mysuru
20

192. Dept
of
Mechanical
Engg,
ATMECe,
Mysuru
21

193. Cutting terminology
• Speed : it is the peripheral speed of the work piece per unit
time. (m/min)
• Feed : it is the distance travelled by the tool during each
revolution of the work piece. (mm/revolution).
• Depth of cut : it is the perpendicular distance measured from
the original surface to the machined surface of the work
piece. (mm)
•
Dept
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Engg,
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194. Dept
of
Mechanical
Engg,
ATMECe,
Mysuru
23

195. Dept
of
Mechanical
Engg,
ATMECe,
Mysuru
24

196. Dept
of
Mechanical
Engg,
ATMECe,
Mysuru
25

197. Dept
of
Mechanical
Engg,
ATMECe,
Mysuru
26

198. BROACHING MACHINE

199. Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
2

200. • It is a multiple tooth
cutting operation with the
tool reciprocating as in
sawing machine.
• Machining operation
completed in a single
stroke.
• Teeth are at a gradually
increasing height.
• Broach are originally
developed for machining
internal keyways.
• It is extensively used in
mass automobile
component manufacture
for various other surfaces.
Dept
of
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Engg,
ATMECE,
Mysuru
3

201. Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
4

202. Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
5

203. BROACHING
• a multiple tooth cutting tool
• the forming tool moves linearly relative to the
workpiece in the direction of the tool axis
• Movement through or along the part
Dept of Mechanical Engg, ATMECE,
Mysuru 6

204. Broaching machines
•vertical ►
•horizontal ▼
Dept of Mechanical Engg, ATMECE,
Mysuru 7

205. • Mostly all are pull type.
• Both internal and external broaching can be done.
• Consists of a box type bed having length is twice the length
of stroke.
• All modern machines are provided with hydraulic drive
housed in the bed.
• Job located in the adapter which is fitted on front vertical
face.
• Small end is connected to hole of the job, then connected
to pulling end which is mounted on front end of ram.
• Ram is connected to hydraulic drive.
• Rear end is supported by guide.
Horizontal Broaching machine
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
8

206. Horizontal Broaching machine
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
9

207. -Cutting speed- 4 to 15 mpm.
-Return speed- 35 mpm.
-Automatic stops are provided to control the
stroke of ram.
-Used for small works like key ways splines,
gun barrel
-refilling, cutting internal and external gears
with helix angle less than 150
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
10

208. Vertical broaching machine
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
11

209. Applications of broaching
• Examples of internal
shapes that can be
done on broaching
machine.
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
12

210. Specification of broaching machine
• Power of the motor and its speed
• Length of bed
• Length of slide stroke
• Rated pulling force
• Cutting stroke speed
• Number of speeds
• Return stroke speed
• Maximum size of cut
• Weight of machine
• Size and floor area
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
13

211. Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
14

212. Broach tool nomencluture
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
15

213. • Pull end- connected to pulling head of broaching machine.
• Front pilot- this locates the broach centrally with the hole to
be broached.
• Roughing teeth and semi finished teeth- used for removing
most of metal in broaching.
• Finishing teeth- meant for finishing the hole to the size and
shape.
• Rear pilot- meant for giving support to the broach after the
last tooth leaving the work piece.
• Land- top portion of teeth.
• Clearance or back off angle- back of the tooth sloped to
give clearance angle.
• Rake or face angle- angle made by sloping the front face of
tooth. Depends upon workpiece material.
• Pitch- linear distance between one tooth to the next tooth.
It is more in roughing teeth than finishing teeth.
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
16

214. Broaching tool
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
17

215. Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
18

216. Broaching tool
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
19

217. External broaching tool
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
20

218. Broaching process
• on a press – the tool is pushed
• on a broaching machine – the tool is pulled
• Using special machine – stationary broach
Dept of Mechanical Engg, ATMECE,
Mysuru 21

219. Broached shapes
• Internal – holes and other round shapes, keyways, profiles,
gears
– Need leading hole to place the pilot
• External – faces, T-shape, co-planar surfaces, gears
• Holes calibration – Broach diameter slightly bigger than the
hole.
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
22

220. Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
23

221. Keyway broaches
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
24

222. Rotary broaching
• internal
Dept
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Engg,
ATMECE,
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25

223. Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
26

224. Rotary broaching - limitations
Dept
of
Mechanical
Engg,
ATMECE,
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Broach length
Spiraling

225. Broaching limitions
• Machined volume
• Limited by chip thickness long broach
• Speed
• No wear demands  low temperature, forces
• Tool costs
• Expensive production long tool life
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
28

226. broaching
Dept
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Mechanical
Engg,
ATMECE,
Mysuru
29

227. Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
30

228. The end

229. NON TRADITIONAL MACHINE

230. Non-traditionalMachiningProcesses
Manufacturing processes can be broadly divided into two groups:
a) primary manufacturing processes : Provide basic shape and size
b) secondary manufacturing processes : Provide final shape and size with
tighter control on dimension, surface characteristics
Material removal processes once again can be divided into two groups
1. Conventional Machining Processes
2. Non-Traditional Manufacturing Processes or non-conventional
Manufacturing processes
Conventional Machining Processes mostly remove material in the form
of chips by applying forces on the work material with a wedge shaped
cutting tool that is harder than the work material under machining
condition.

231. Non-traditionalMachiningProcesses
The major characteristics of conventional machining are:
• Generally macroscopic chip formation by shear deformation
• Material removal takes place due to application of cutting forces –
energy domain can be classified as mechanical
• Cutting tool is harder than work piece at room temperature as
well as under machining conditions
Non-conventional manufacturing processes is defined as a group of
processes that remove excess material by various techniques
involving mechanical, thermal, electrical or chemical energy or
combinations of these energies but do not use a sharp cutting tools
as it needs to be used for traditional manufacturing processes.
The major characteristics of Non-conventional machining are:
1. Material removal may occur with chip formation or even no chip
formation may take place. For example in AJM, chips are of
microscopic size and in case of Electrochemical machining material
removal occurs due to electrochemical dissolution at atomic level.

232. Non-traditionalMachiningProcesses
The major characteristics of Non-conventional machining:
2. In NTM, there may not be a physical tool present. For example in laser
jet machining, machining is carried out by laser beam. However in
Electrochemical Machining there is a physical tool that is very much
required for machining
3. In NTM, the tool need not be harder than the work piece material. For
example, in EDM, copper is used as the tool material to machine
hardened steels.
4. Mostly NTM processes do not necessarily use mechanical energy to
provide material removal. They use different energy domains to
provide machining. For example, in USM, AJM, WJM mechanical
energy is used to machine material, whereas in ECM electrochemical
dissolution constitutes material removal.

233. Classificationof NTM processes
classification of NTM processes is carried out depending on the nature of
energy used for material removal.
1. Mechanical Processes
• Abrasive Jet Machining (AJM)
• Ultrasonic Machining (USM)
• Water Jet Machining (WJM)
• Abrasive Water Jet Machining (AWJM)
2. Electrochemical Processes
• Electrochemical Machining (ECM)
• Electro Chemical Grinding (ECG)
• Electro Jet Drilling (EJD)
3. Electro-Thermal Processes
• Electro-discharge machining (EDM)
• Laser Jet Machining (LJM)
• Electron Beam Machining (EBM)
4. Chemical Processes
• Chemical Milling (CHM)
• Photochemical Milling (PCM)

234. Needsfor NonTraditional Machining
• Extremely hard and brittle materials or Difficult to machine materials are
difficult to machine by traditional machining processes.
• When the workpiece is too flexible or slender to support the cutting or
grinding forces.
• When the shape of the part is too complex.
• Intricate shaped blind hole – e.g. square hole of 15 mmx15 mm with a
depth of 30 mm
• Deep hole with small hole diameter – e.g. φ 1.5 mm hole with l/d = 20
• Machining of composites.

235. AbrasiveJet Machining
In Abrasive Jet Machining (AJM), abrasive particles are made to impinge
on the work material at a high velocity. The high velocity abrasive particles
remove the material by micro-cutting action as well as brittle fracture of the
work material.

236. AbrasiveJet Machining
In AJM, generally, the abrasive particles of around 50 μm grit size would
impinge on the work material at velocity of 200 m/s from a nozzle of I.D. of
0.5 mm with a stand off distance of around 2 mm. The kinetic energy of
the abrasive particles would be sufficient to provide material removal due
to brittle fracture of the work piece or even micro cutting by the abrasives.

237. AbrasiveJet Machining
AJM set-up

238. AbrasiveJet Machining
Process Parameters and Machining Characteristics
Abrasive : Material – Al2O3 / SiC
Shape – irregular / spherical
Size – 10 ~ 50 μm
Mass flow rate – 2 ~ 20 gm/min
Carrier gas : Composition – Air, CO2, N2
Density – Air ~ 1.3 kg/m3
Velocity – 500 ~ 700 m/s
Pressure – 2 ~ 10 bar
Flow rate – 5 ~ 30 lpm
Abrasive Jet : Velocity – 100 ~ 300 m/s
Mixing ratio – mass flow ratio of abrasive to gas
Stand-off distance – 0.5 ~ 5 mm
Impingement Angle – 600 ~ 900
Nozzle : Material – WC
Diameter – (Internal) 0.2 ~ 0.8 mm
Life – 10 ~ 300 hours

239. AbrasiveJet Machining
effect of process parameters on MRR

240. AbrasiveJet Machining

241. AbrasiveJet Machining
Modelling of material removal
Material removal in AJM takes place due to brittle fracture of the work
material due to impact of high velocity abrasive particles.
Modelling has been done with the following assumptions:
(i) Abrasives are spherical in shape and rigid. The particles are
characterised by the mean grit diameter
(ii) The kinetic energy of the abrasives are fully utilised in removing
material
(iii) Brittle materials are considered to fail due to brittle fracture and
the fracture volume is considered to be hemispherical with diameter
equal to chordal length of the indentation
(iv) For ductile material, removal volume is assumed to be equal to
the indentation volume due to particulate impact.

242. Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
14

243. USM
• USM for machining brittle work material
• Material removal primarily occurs due to the indentation of the hard
abrasive grits on the brittle work material.
• Other than this brittle failure of the work material due to indentation
some material removal may occur due to free flowing impact of the
abrasives against the work material and related solid-solid impact
erosion,
• Tool’s vibration – indentation by the abrasive grits.
• During indentation, due to Hertzian contact stresses, cracks would
develop just below the contact site, then as indentation progresses
the cracks would propagate due to increase in stress and ultimately
lead to brittle fracture of the work material under each individual
interaction site between the abrasive grits and the workpiece.
• The tool material should be such that indentation by the abrasive
grits does not lead to brittle failure.
• Thus the tools are made of tough, strong and ductile materials like
steel, stainless steel and other ductile metallic alloys.
Dept
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15

244. USM
• Process variables:
• Amplitude of vibration (ao) – 15 – 50 μm
• Frequency of vibration (f) – 19 – 25 kHz
• Feed force (F) – related to tool dimensions
• Feed pressure (p)
• Abrasive size – 15 μm – 150 μm
• Abrasive material – Al2O3
- SiC
- B4C
- Boronsilicarbide
- Diamond
Flow strength of work material
Flow strength of the tool material
Contact area of the tool – A
Volume concentration of abrasive in water slurry – C
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
16

245. USM Equipment
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
17

246. Modelling
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
18

247. Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
19

248. Modelling
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
20

249. Modelling
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
21

250. Modelling
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
22

251. Modelling
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
23

252. WaterJet andAbrasiveWaterJet Machining
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
24

253. WaterJet andAbrasiveWaterJet Machining
• WJM - Pure
• WJM - with stabilizer
• AWJM – entrained – three phase –
abrasive, water and air
• AWJM – suspended – two phase –
abrasive and water
o Direct pumping
o Indirect pumping
o Bypass pumping
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
25

254. GeneralExperimentalconditions
Orifice – Sapphires – 0.1 to 0.3 mm
Focussing Tube – WC – 0.8 to 2.4 mm
Pressure – 2500 to 4000 bar
Abrasive – garnet and olivine - #125 to #60
Abrasive flow - 0.1 to 1.0 Kg/min
Stand off distance – 1 to 2 mm
Machine Impact Angle – 60o to 900
Traverse Speed – 100 mm/min to 5 m/min
Depth of Cut – 1 mm to 250 mm
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
26

255. WaterJet andAbrasiveWaterJet Machining
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
27

256. WaterJet andAbrasiveWaterJet Machining
• Extremely fast set-up and programming
• Very little fixturing for most parts
• Machine virtually any 2D shape on any material
• Very low side forces during the machining
• Almost no heat generated on the part
• Machine thick plates
Advantages of AWJM
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
28

257. Componentsof AWJM
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
29

258. Components of AWJM
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
30

259. Componentsof AWJM
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
31

260. Componentsof AWJM
Catcher
(c) catcher plates (TiB2)
(b) steel/WC/ceramic balls
(a) water basin
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
32

261. Modelling
Photographic view of kerf (cross section)
Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
33

262. Dept
of
Mechanical
Engg,
ATMECE,
Mysuru
34