A brief overview of metal cutting, tools, and factors.

1. METAL CUTTING
AND CUTTING
TOOLS
By: 1915127, 1915128, 1915129, 1715121

2. INTRODUCTION
◦ METAL CUTTING is the process of removing
unwanted material in the form of chips, from a
block of metal, using cutting tool . The various
cutting processes fall into two groups:
• Continuous contact Cutting: Turning, shaping,
drilling, etc.
• Intermittent Cutting: Milling, Honing, Grinding, etc.
◦ A METAL CUTTING TOOL is a tool which is
used to remove material from a metal work
piece through the process of shear deformation.
The cutting process may be achieved by using a
single-point or multi-point tool.

3. RELATIVE MOTION FOR VARIOUS CUTTING
OPERATIONS
The process of metal cutting in which chip is formed is affected by
a relative motion between the workpiece and the hard edge of a
cutting tool held against the workpiece.
TYPES OF CUTTING TOOL
Chip removal in the metal cutting process may
be performed either by cutting tools having
distinct cutting edged or by abrasives. Cutting
tools are divided in two groups:
• SINGLE POINT TOOLS:
A single-point cutting tool can be used for
increasing the size of holes, or boring. Turning
and boring are performed on lathes and boring
mills.
• MULTIPLE POINT TOOLS:
Multiple-point cutting tools have two or more
cutting edges and include milling cutters, drills,
and broaches.
Operation Motion of job Motion of cutting tool
Turning Rotary Froward translation
Boring Forward Translation Rotation
Drilling Fixed Rotation as well as translatory feed
Planing Translatory Intermittent Translation
Milling Translatory Rotation
ORTHOGONAL AND OBLIQUE CUTTING
The two basic methods of metal cutting using a
single point tool are:
• ORTHOGONAL or TWO DIMENSIONAL:
Orthogonal cutting takes place when the cutting
face of the tool is perpendicular to the line of
action or path of the tool.
• OBLIQUE or THREE DIENSIONAL:
Oblique cutting takes place when the cutting face
is inclined at an angle less than 90degree to the
path of the tool .

4. Ideal Cutting Tool materials
◦ Hardness – the material must remain harder than the work piece material at
elevated temperatures. Hardness is the resistance a material bears when rubbed
against a flat surface predetermined scratched/
◦ Resistance to Wearing –Having an acceptable tool life before being replaced. The
material needs to withstand excessive wear and tear while the relative hardness of
tool and work piece change.
◦ Toughness- It implies combination of ductility and strength. The material must
withstand sudden shocks and vibrations.
◦ Coefficient of friction – for obvious reasons the coefficient of friction between
workpiece and tool material must remain low to keep the heat generation low and
wear and tear minimum.
◦ The Cost and Easeness of Fabrication must be within reasonable limits.

5. Major Cutting Tool Materials
1. Carbon
Steel
2. Medium
Alloy Steel
3. High Speed
Steel
4. Stellites
Carbon
content
ranges from
0.8 to 1.5%.
Used to make
cheap, easy
to forge tools
requiring low
cutting speed.
Carbon content
is similar to
plain carbon
steels, besides
upto 5% alloy
of chromium ,
molybdenum,
tungsten and
vanadium.
This greatly
improves
hardness
resistance to
wear.
Characteristically
retains hardness
upto 900 TC,
higher wear
resistance, 2-3
times higher
operational
speeds than
carbon steels.
Alloy contains 40-48% cobalt, 30-35% chromium
and 12-19% tungsten.
They can’t be forged to shape but directly
deposited to the surface by an oxy acetylyne
flame. Retains hardenss until 1000TC and
operated on steel at speed 2 times higher than
HSS.

6. 5. Cemented
Carbides
6. Ceramics 7. Diamond 8. Abrasives
Composed principally
of carbon mixed with
other elements. Most
commonly “tungsten
carbide” an extremely
hard alloy.
Cemented are
carbides are
remarkably resistant to
heat and wear.
They retain properties
upto 1000 TC and 6
times higher cutting
speed than HSS.
Recent metal cutting
tools Aluminium oxide
referred to as
ceramics.
Ceramic tools are
made by pressing
AlO2 in a mould to
280kg/cm3 pressure
and then sintering at
2200TC.
Usually used for single
point tool for semi
finishing and finishing
Cast Iron in turning
operations,.
Widely known as the
hardest material.
It can comfortably be
run at cutting speed 50
times higher than HSS
and retains its features
at temperatures upto
1500TC.
It inherits
incompressibility due
to its long grain
structure.
Suitable for cutting
very hard work pieces
like glass, plastics.
Abrasives are mainly
used for grinding hard
tools where finish is
required on hardened
or unhardened
materials.
They are widely used
in different forms-
loose, bonded into
wheels and stones
and embedded in
papers and cloth.

7. Select disadvantages of prominent cutting materials
◦ Low-carbon steels suffer from yield-point runout and beyond a point can’t be
loaded and thus limited in applications . Mild Steel has relatively low tensile
strength compared to HSS.
◦ High speed steel arguably does not provide fine and detailed finish to the work
piece. Inferior to cemented carbide, ceramics and diamond and is thus
relevantly engaged.
◦ Ceramics bit more brittle than carbides and thus have lower resistance of
mechanical shocks and vobrations.
◦ Using diamond tools includes the occurrence of pollution for the material and
working environment, micro-cracking and a loss of the material cut due to
finite thickness of the tool.

8. Applications
◦ Rigid low horsepower machine tools are made of high speed steel. Drills, thread
chasers and gears too are made of HSS
◦ Ceramics have application in face milling and turning, Suited for machining cast irons,
super alloys and hard steel.
◦ Diamond tools are used to gain high processing precision and efficiency . Medium or
small sized diamond saw blades, diamond grinding are often used in repairing roads
processing building materials.
◦ Carbon steel is used primarily to make the less expensive drills, taps, and
reamers. Carbon steel is seldom used to make single-point cutting tools.