This presentation contains various aspects of metal cutting like mechanics of chip formation, single point cutting tool, chip breakers, types of chips,etc

1. PRESENTATION PREPARED BY :
KUNJ THUMMAR
140050119517
METAL CUTTING

2. CONTENTS
1. Introduction
2. Mechanics of chip formation
3. Single point cutting tool and its designation
4. Methods of machining
5. Types of chips
6. Forces on single point cutting tool
7. Chip Breakers
8. Specific cutting pressure

3. INTRODUCTION
 Metal cutting or machining is the process of
producing workpiece by removing unwanted material
from a block of metal, in the form of chips.
 This process is most important because almost all
products get their final shape and size directly or
indirectly by machining.
 Its major drawback is that in this process there is a
lot of material lost in the form of chips.

4. MECHANICS OF CHIP FORMATION
 A wedge shaped tool is made to move relative to the
workpiece.
 As the tool makes contact with the workpiece it
exerts pressure on it resulting in compression of the
metal near the tool tip.
 This induces shear – type deformation within the
metal and it starts moving upward along the face of
the tool.
 As the tool advances this process of shearing goes
on increasing and material is removed.

5. MECHANICS OF CHIP FORMATION
Fig. 2.1

6. CHIP FORMATION IN DUCTILE MATERIALS
 As the tool makes contact with
the workpiece it results in
exerting pressure on the
material in front of it.
 This causes the shear
deformation in the workpiece
and the metal starts moving up
in laminar form along the face
of the tool.
 This is also known as
Pispannen’s model of chip
formation.
Fig. 2.2

7. CHIP FORMATION IN BRITTLE MATERIALS
 Cracks develop in the
workpiece near the tool tip.
 This crack results in stress
concentration.
 Hence, crack propagation
intensity increases and the
chip detaches itself from the
base material.
 This results in a
discontinuous, irregular
shape and sized chip.
Fig. 2.3

8. SINGLE POINT CUTTING TOOL
• It consists of a sharpened cutting edge called its
point .
• The point is bounded by the face, the side flank, the
end flank and the base.
• The side cutting edge is formed by intersection of
face and side flank.
• The end cutting edge is formed by intersection of
face and end flank.
• The point where end and side cutting edge meets is
called the nose of the tool.

9. SINGLE POINT CUTTING TOOL
Fig. 3.1

10. TOOL DESIGNATION
 By designation or nomenclature of the tool we mean
the designation of the shape of the tool.
 There are two systems widely used for tool
designation :
• ASA System ( American standards association
system ) or ANSI System ( American National
standards Institute system ).
• ORS ( Orthogonal Rake system)

11. TOOL DESIGNATION BY ASA SYSTEM
In this system the angles of the tool face i.e. its slope,
are defined in two orthogonal plane, one parallel to
and another perpendicular to the axis of cutting tool.
Fig. 3.2

12. TYPES OF RAKES
Fig. 3.3

13. TYPES OF RAKES
The use of positive rake is
recommended in following
conditions :
• While machining low
strength ferrous and non
ferrous materials.
• When low power machines.
• When machining long shafts
of low diameters.
• When the set up lacks
strength and rigidity.
• When cutting is done at low
speeds.
The use of negative rake is
recommended in following
conditions :
• While machining high
strength alloys.
• When there are high impact
loads.
• When there are highly rigid
setups.
• When cutting is done at high
speeds.

14. In this system the planes for designation tools are the
planes containing the principle or side cutting edge
and the plane normal to it.
TOOL DESIGNATION BY ORS SYSTEM
Fig. 3.4

15. TOOL DESIGNATION BY ORS SYSTEM
Fig. 3.5

16. METHODS OF MACHINING
 In the cutting operation the tool is wedge shaped and
has a straight cutting edge.
 Basically, there are two methods of metal cutting,
depending upon the arrangement of the cutting edge
w.r.t. the direction of relative tool work motion :
1. Orthogonal cutting
2. Oblique cutting

17. ORTHOGONAL CUTTING
 Orthogonal cutting is a type of metal cutting in which
the cutting edge of wedge shape cutting tool is
perpendicular to the direction of tool motion.
 In this cutting the cutting edge is wider than width of
cut.
 In this case the chip slides directly up the tool face.
Fig. 4.1 Fig. 4.2

18. OBLIQUE CUTTING
 In oblique cutting, the cutting edge of the tool is set at an
angle other than 90˚ with respect to the direction of the
velocity vector of the tool.
 In this case lateral direction of chip movement is obtained.
Fig. 4.3

19. DIFFERENCE BETWEEN ORTHOGONAL AND
OBLIQUE CUTTING
ORTHOGONAL CUTTING OBLIQUE CUTTING
Cutting edge is perpendicular to tool
travel.
Cutting edge is inclined at an angle less
than 90˚.
Direction of chip flow is perpendicular to
the cutting edge.
The chip flows on the tool face making an
angle.
The chip coils in a tight flat spiral. The chip flows in sideways in a long curl.
Life of tool in less. Tool life is more.
Produces sharp corners. Produces a chamfer at the end of a cut.
Smaller length of cutting edge is in contact
with the job.
For the same depth of cut the greater
length of cutting edge is in contact with the
job.
Generally parting off in lathe, broaching
and slotting operations are done by this
tool.
This method is used in all most all
machining processes.
Table 4.1

20. CHIPS AND ITS TYPES
The waste/dust material produced while machining
any surface is termed as chip. Depending on the
workpiece material and the cutting conditions, the
following types of chip formation can be distinguished.
 Continuous chips
 Discontinuous chips
 Continuous chips with built up edges (BUE)

21. CONTINUOUS CHIPS
 If the metal chips formed during machining is without
segments i.e. without breakage, than it is called as
continuous types of chips.
 Continuous chips are formed when the ductile material is
machined with high cutting speed and minimum friction
between the chip and tool face.
Fig. 5.1

22. CONTINUOUS CHIPS
 The conditions which are
responsible for the formation
of continuous types of chips
are :
I. Ductile material like mild
steel is used.
II. Bigger rake angle of the
tool.
III. High cutting speed.
IV. Minimum friction between
the chip and tool interface.
V. Small depth of cut.
• Advantages :
I. Better surface finish to the
ductile material.
II. Less heat generation due to
minimum friction between
the tool face and chip.
III. Low power consumption.
IV. Long tool life due to less
wear and tear.

23. DISCONTINUOUS CHIPS
 If the chips formed during machining process is not
continuous i.e. formed with breakage is called
discontinuous chips.
 Discontinuous types of chips are formed when hard and
brittle metals like brass, bronze and cast iron is machined.
Fig. 5.2

24. DISCONTINUOUS CHIPS
Conditions which are responsible
for the formation of discontinuous
chips are :
Low feed rate.
I. Small rake angle of the tool.
II. High cutting speed.
III. High friction forces at the chip
tool interface.
IV. Too much depth of cut.
Advantages :
The formation of discontinuous
types of chips in brittle materials
provides good surface finish,
increases the tool life and reduces
the consumption of power.
Disadvantages :
When discontinuous chips are
formed in the ductile materials,
the workpiece result in poor
surface finish and excessive wear
and tear of the tool takes place.

25. CONTINUOUS CHIP WITH BUILT UP EDGE
 Continuous chips with built up edge is formed by machining
ductile material with high friction at the chip-tool interface.
 It is similar to the continuous types of chips but it is of less
smoothness due to the built up edge.
Fig. 5.3

26. FORMATION OF BUILT UP EDGE
• When the chip flows in upward direction there exist high
friction in between the interface of the chip and tool.
• Due to the high friction between the chip and tool a very
intense heat is generated at the nose of the tool.
• The compressed metal adjacent to the tool nose gets
welded to it. This compressed metal welded to the nose is
called built up edge.
• Due to formation of the built up edge the rake angle of the
tool gets changed and so is the cutting force.

27. CONTINUOUS CHIP WITH BUILT UP EDGE
The factors which are
responsible for promoting the
formation of the BUE chips are:
 Excessive feed rate.
 Small rake angle of the tool.
 Low cutting speed.
 Lack of coolant and this
increase the friction between
the chip tool interfaces.
Advantages :
The making of the BUE has
one advantage i.e. it protects
the tool from getting damaged
from high friction and
temperature generated during
machining process and hence
the tool life increases.
Disadvantages :
The formation of these types
of chips results in rough
surface finish, change in the
rake angle and cutting forces.

28. COMPARISON BETWEEN ALL CHIP TYPES
S.
no
Factors Continuous
Chips
Discontinuous
Chips
Continuous
chips with
Built Up
Edge (BUE)
1. Material
types
Ductile Brittle, ductile
but hard
Ductile
2. Rake angle Large Small Small
3. Cutting
speed
High Medium or high Low or
medium
4. Friction
between
chip tool
interface
Minimum Maximum Maximum
5. Depth of
cut
Small High Medium
Table 5.1

29. FORCE ON A SINGLE POINT TOOL
 The work material offers resistance to the cutting tool,
during metal cutting.
 This resistance is overcome by the cutting force applied to
the tool face.
 The work done by this force in cutting is expended in
shearing the chip from the work, deforming the chip and
overcoming the friction of the chip on the tool face and tool
flank on the cutting surface.
 Magnitude of this force depends upon :
- material being machined - tool angles
- rate of feed - cutting speed
- depth of cut - coolant used

30. FORCE ON A SINGLE POINT TOOL
Fig. 6.1

31. CHIP BREAKERS
 Continuous chips produced while machining ductile
materials often causes difficulties of handling because they
occupy considerable space and have sharp edges.
 They may also be hot.
 They also get entangled and start rotating with the job.
 Hence, it is desirable to break these chips into short
convenient length for their proper disposal. This operation
of chip breaking is done by chip breakers.
 Chip breakers are classified as :
I. Groove type
II. Obstruction type

32. CHIP BREAKERS
Groove type chip
breaker :
A small groove is provided
behind the leading cutting
edge of the tool insert on
the rake face .The geometry
of groove determines
the radius of the chip
curvature.
Fig. 7.1

33. CHIP BREAKERS
Obstruction type chip
breaker :
Obstruction type either integral
or attached to the cutting tool.
Attached chip breakers can be
made adjustable to the
different cutting condition. One
of the advantage of obstruction
type chip breaker is that it
cause less wear on tool face
than groove type chip breaker
Fig. 7.2

34. CHIP BREAKERS
Advantages :
 Ensure safety for operator.
 Increase tool life.
 Facilitate the removal of chips from cutting zone.
 Reduce the cutting resistance and vibration, hence
increase machine performance.
 Machined surface do not get spoiled by
continuous chips.
 Increase productivity (decrease time loss) – small chips
take less volume than continuous chip, so it does not
need chip disposal as frequent as continuous chip.

35. CHIP BREAKERS
Disadvantages of chip breaker :
 Frequent chip braking and hitting at flank of tool may
causes harmful vibration.
 Some cases the use of chip breaker causes the
spoilage of surface finish quality.
 Heat and stress concentrated at sharp cutting edge,
results the rapid failure of cutting edge.

36. BIBLIOGRAPHY
 A Text book of manufacturing technology by R.K.
Rajput – Laxmi publications.
 A Text book of production engineering by P.C. Sharma
– Chapter no. 14 – S. Chand and company Limited,
2006 Edition, ISBN 81-219-0421-8.
 Manufacturing process II – Lecture by Dr. V.K. Jain
Indian Institute of technology, Kanpur.
 Images from www.google.com
 www.mecholic.com
 www.mechanicalbooster.com