Tools material for cutting for engineering

1. MFGE 307THEORY OF MANUFACTURING TECHNOLOGY II
Chapter 4
CUTTING TOOLS:
Material and Geometry
Prof. Dr. S. Engin KILIÇ
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2. MFGE 307THEORY OF MANUFACTURING TECHNOLOGY II
Tools must be so selected that they can cut properly and efficiently
under the selected cutting conditions which may lead to a harsh
cutting environment due to high cutting temperatures and high
cutting pressures.
In selection two principal aspects must be considered:
a) tool geometry b) tool material.
The geometry  the optimum performance for the given
tool material and the operation.
The tool material  highest possible strength, resistance and durability
against forces, temperatures and wearing action
during machining
Cutting Tools
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3. MFGE 307THEORY OF MANUFACTURING TECHNOLOGY II
Cutting Tools - Geometry
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The cutting tool geometry is of prime importance because it directly affects:
1. Chip control: The tool geometry defines the direction of chip flow. This direction
is important to control chip breakage and evacuation.
2. Productivity of machining: The cutting feed per revolution is considered the
major resource in increasing productivity. This feed can be significantly increased
by adjusting the tool cutting edge angle. For example, the most common use of this
feature is found in milling, where increasing the lead angle to 45° allows the feed
rate to be increased 1.4-fold. As such, a wiper insert is introduced to reduce the feed
marks left on the machined surface due to the increased feed.
3. Tool life: The geometry of the cutting tool directly affects tool life as this
geometry defines the magnitude and direction of the cutting force and its
components, the sliding velocity at the tool–chip interface, the distribution of the
thermal energy released in machining, the temperature distribution in the cutting
wedge etc.

4. MFGE 307THEORY OF MANUFACTURING TECHNOLOGY II
Cutting Tools - Geometry
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4. The direction and magnitude of the cutting force and thus its components:
Four components of the cutting tool geometry, namely, the rake angle, the tool
cutting edge angle, the tool minor cutting edge angle and the inclination angle,
define the magnitudes of the orthogonal components of the cutting force.
5. Quality (surface integrity and machining residual stress) of machining:
The correlation between tool geometry and the theoretical topography of
the machined surface is common knowledge. The influence of the cutting
geometry on the machining residual stress is easily realized if one recalls
that this geometry defines to a great extent the state of stress in the deformation
zone, i.e., around the tool.

5. MFGE 307THEORY OF MANUFACTURING TECHNOLOGY II
Kalpakjian-Schimid, 2008
Cutting Tools - Geometry
(a) Schematic illustration of a right-hand cutting tool for turning. Although these tools have traditionally been
produced from solid tool-steel bars, they are now replaced by inserts of carbide or other tool materials of various
shapes and sizes, as shown in (b).
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6. MFGE 307THEORY OF MANUFACTURING TECHNOLOGY II
Cutting Tools - Geometry
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7. MFGE 307THEORY OF MANUFACTURING TECHNOLOGY II
Side Rake Angle (gs):
 great influence on chip formation
less deformation of removed layer of w.p.
 as increased  less resistance to chip formation
lower cutting forces
lower power consumption
less heat transfer area on rake
 substantial increase  weakening of cutting edge
catastrophic tool failure
Cutting Tools - Geometry
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8. MFGE 307THEORY OF MANUFACTURING TECHNOLOGY II 8
Cubic Boron Nitrade (Cont’d)
 CBN can be most economically used in machining hardened
steel (60-68 Rc) and chilled CI at speeds (45-60 m/min) and
feeds of 0.2-0.4 mm/rev.
 Long tool life so that rolls may be machined to a dimensional
tolerance and surface finish which eliminate grinding
operation.
 High hot hardness value.
 Excellent abrasive resistance and resistance to react with
ferrous materials.
 Good toughness when used with negative rake and chamfers
can be used for interrupted cutting of hardened steel.

9. MFGE 307THEORY OF MANUFACTURING TECHNOLOGY II 9
Diamonds
 Hardest of all materials.
 Used in operations where other tools cannot perform effectively.
 Have much lower wear rate and longer tool life than carbides and
ceramics where abrasion is dominant wear mechanism.
 Single crystal natural diamonds are used to produce surfaces of
extremely high accuracy and finish. (e.g. optical instruments and gold
jewellery).
 Deficient in toughness, easy chipping of cutting edges.
 Polycrystalline diamond tools are made with a layer of consolidated
synthetic diamonds (0.5 - 1 mm thick) bonded on cemented carbide
substrates (2 - 2.5 mm thick).

10. MFGE 307THEORY OF MANUFACTURING TECHNOLOGY II 10
Diamonds (Cont’d)
 Cost 20-30 times the equivalent carbide tool.
 Edges less sensitive to accidental damage.
 Maintain exceptional wear resistance.
 Recommended for machining aluminium alloys (speeds can be over
500 m/min with long life).
 Also used in machining copper and copper alloys and cemented
carbides in pre-sintered condition.
 Not used for high speed machining of steel and nickel because of
excessive wear.
 Diamond does not revert to graphitic form in the absence of air at
temperatures below 1500oC.
 In contact with iron, graphitization begins just over 730oC.

11. MFGE 307THEORY OF MANUFACTURING TECHNOLOGY II 11
Hardness of Tool Materials

12. MFGE 307THEORY OF MANUFACTURING TECHNOLOGY II 12
Hardness of Tool Materials
Viktor P. Astakhov and J. Paulo Davim