This presentation includes Tool life , Types of tool wear, tool wear mechanisms and factors affectin tool life

1. APPA
INSTITUTE OF ENGINEERING & TECHNOLOGY, KALABURAGI
DEPARTMENT OF MECHANICAL ENGINEERING
DATE: 13TH MAY 2017
TIME: 10:30-12:30
CLASS: 4TH SEM “B”
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By:
Asst.Prof. PRASHANT MULGE
B.E., M.Tech.,(Ph.D.)

2. 1. What is tool wear/ tool failure?
2. Reasons for tool wear.
3. What happens if tool wear /fails?
4. Types of tool wear.
5. Tool wear mechanisms.
6. What is Tool life?
7. Taylor’s Tool life equation.
8. Factors affecting tool life.

3. WHAT IS TOOL WEAR/ TOOL FAILURE?
 Wear is the loss of material from the surface.
 The wear means that the tool loses its volume and
geometrical properties.
 Tool wear describes the gradual failure of cutting tools
due to regular operation.
 If the tool is not giving the satisfactory performance then
it is an indication of the tool failure.
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4. REASONS FOR TOOL WEAR
Thermal softening.
Rupture of cutting edge
Gradual wear
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5. WHAT HAPPENS IF TOOL WEAR /FAILS?
increased cutting forces.
increased cutting temperatures.
poor surface finish.
decreased accuracy of finished part.
May lead to tool breakage.
Causes change in tool geometry
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6. TYPES OF TOOL WEAR.
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FLANK WEAR
CRATER WEAR

7. FLANK WEAR
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 flank wear in which the portion of the tool in contact with the
finished part erodes.
 Flank wear is a form of wear, which appears on the flank, below
the cutting edge of the tool.
 It occurs due to the abrasion between the flank of the tool and the
newly machined work piece surface.
 Flank wear will be more near the nose of the tool, and it is not
uniform along the cutting edge.
 This type of wear occurs on all tools while cutting any type of work
material.

8. CRATER WEAR
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 crater wear in which tool contact with chips erodes the
rake face.
 Crater wear generally takes place while machining
ductile materials in which the continuous chip produced
gets curled and flows over the face of the cutting tool.
 During this process , the pressure of the hot chip
rubbing and sliding up the face of the cutting tool
results in the formation of a crater or depression at the
tool-chip interface.

9. TOOL WEAR MECHANISMS.
1. Abrasive wear
2. Adhesion wear
3. Diffusion
4. Oxidation
5. Fatigue
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10. ABRASIVE WEAR
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 Softer material sliding over the
face of hard material may contain
appreciable concentration of hard
particles
 Hard particles act as small cutting
edge like grinding wheel
 Hard particles result worn out of
tool material
 Particles of hard material are
intermittently turn out from the
surface and dragged along the
surface.

11. ADHESION WEAR
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 When softer metal slide over hard metal ,
parts of soft metal adhere high spots on the
metal due to:
 Friction
 High temperature
 Pressure
 The spots result irregular flow of chip over
the face and build up of more particles on
the tool
 Finally the built up edges will transform
the surface result uneven structure on the
tool surface

12. DIFFUSION
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 When a metal is in sliding contact with another
metal the temperature at the interface is high
 The high temperature allows the atoms of hard
material to diffuse into softer material matrix
 hence the strength and abrasiveness of the softer
material Increase
 Atoms of the softer metal may also diffuse into
harder medium, thus weakening the surface of
harder material medium
 •Diffusion phenomenon is strongly dependent
on temperature

13. OXIDATION
Oxidation is the result of reaction between tool
face and oxygen
Ex. When machining steel work piece with HSS or
cemented carbide tool , groove formation is greatly
accelerated if the cutting zone is subjected to a jet
oxygen.
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14. FATIGUE WEAR
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 Will occur when two surfaces slides in
contact with other under high pressure.
 Roughness of one surface interlocks with
those of other.
 Due to friction , compressive force will be
produced in one side and tensile on other
side, these phenomenon cause surface
crack.
 The cracks ultimately combines with one
another and lead surface crumble.

15. WHAT IS TOOL LIFE?
DEFINITION:
The tool life is the duration of actual cutting time after
which the tool is no longer usable.
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The tool life is used to calculate the tool material
performance and machinability of work piece material.

16. TAYLOR’S TOOL LIFE EQUATION
VTn = C
Where
V = Cutting speed m/min
T = tool life in min.
n = Tool life index, which
depends on tool material
C = Machining constant
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VTn fa tb= C
Where
f = feed rate in mm/min
t = depth of cut in mm
a & b constant which
depends on mechanical
properties of the work piece

17. FACTORS AFFECTING TOOL LIFE.
1. Cutting speed
2. Feed and depth of cut
3. Tool geometry
4. Tool material
5. Work material
6. Nature of cutting
7. Cutting fluids
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