Lecture 3 (MP-1)

Manufacturing Processes-2
SUBJECT CODE :4ME04
SEM 4
DEPARTMENT OF MECHANICAL ENGINEERING

BY MR.K.P.PAWAR
LECTURER
ANURADHA COLLEGE OF ENGINEERING
*

LECTURE -3
Objectives of Lecture
 To understand basic single point tool geometry
 To learn tool signature system
 To study cutting tool materials

 A tool bit is a non-rotary cutting tool used in metal lathe ,shapers
and planers
 Such cutters are also often referred to by the set-phrase name
of single-point cutting tool, as distinguished from other cutting
tools such as a saw or water jet cutter
 The cutting edge is ground to suit a particular machining
operation and may be re-sharpened or reshaped as needed.
 The ground tool bit is held rigidly by a tool holder while it is
cutting.
Introduction : Single point cutting tool

Basic single point tool geometry

1.Back Rake
 Help to control the direction of the chip, which naturally curves into
the work due to the difference in length from the outer and inner
parts of the cut.
 Helps counteract the pressure against the tool from the work by
pulling the tool into the work.
2.Side Rake
 Along with back rake controls the chip flow and partly counteracts
the resistance of the work to the movement of the cutter
 Can be optimized to suit the particular material being cut.
 Ex. Brass requires a back and side rake of 00while aluminum uses a
back rake of 350 and a side rake of 150

.
3.Nose Radius
 Makes the finish of the cut smoother as it can overlap the previous
cut and eliminate the peaks and valleys that a pointed tool
produces.
 Having a radius also strengthens the tip, a sharp point being quite
fragile.
4.Clearance Angle
 All the other angles are for clearance in order that no part of the
tool besides the actual cutting edge can touch the work.
 The front clearance angle is usually 80while the side clearance
angle is 10 − 150and partly depends on the rate of feed expected.

Tool Signature
 Indicates the angles that a tool utilizes during the cut
 Specifies the active angles of the tool normal to the cutting edge
 Some of the common systems are:
1. American System
2. British System
3. Continental System
4. International System

American System
 Defines the principle angles like side
rack, back rake, nose ,etc. with
regarding to the cutting edge and
without any reference to their
locations.
 This system of nomenclature does
give any indication of the tool
behavior with regards to the flow of
chip during the cutting operation.
 Three reference planes adopted for
designated different tool angles are
similar to conventional machine
drawing.

American System
For example a tool may designated in the following sequence:
8-14-6-6-6-15-1
1. Back rack angle :8
2. Side rack angle : 14
3. End relief angle : 6
4. Side relief angle :6
5. End cutting edge angle: 6
6. Side cutting edge angle :15
7. Nose radius :1mm

British System
This system defines the maximum rake
The variation of tool parameters in this system are indicated in the
order of :
1. Back rake
2. Side rake
3. End relief angle
4. Side relief angle
5. Side cutting edge angle
6. Nose radius

Continental System:
 German System
 Various tool parameters are specified with reference to the tool
reference planes.
International System:
 Internationally adopted system, developed recently.
 Incorporates the salient features of tool nomenclature of
different systems in it.

Cutting Tool Materials
Properties of cutting tool material:
1. Hot hardness
2. Wear & abrasion resistance
3. Impact toughness
4. Increased thermal conductivity
5. Lower co-efficient of thermal expansion
6. Lower chemical & mechanical affinity for the work material
7. Easy to grind & sharpening
8. High specific heat
9. Low coefficient of friction between work & the tool
10. Easy to fix to the tool holder

Selection of tool material depends up on following factors:
1. Type of cutting operation
2. Material of work piece
3. Machine tool to be used & surface finish required

Cutting Tool Materials
Over the years, a wide variety of cutting tool materials have been
developed to meet the ever increasing demand of machining
herder & harder materials.
The various cutting tool materials can be grouped as follows:
1. Plain carbon steel
2. Medium Alloy Steel
3. High Speed Steel
4. Non-ferrous Cast Alloy
5. Cemented Carbides
6. Ceramics or Oxides
7. Cermets
8. Diamond
9. Cubic Boron Nitride(CBN)
10. UCON
11. Sialon
12. Coronite

Carbon tool steels
1.Unstable
2.Very inexpensive
3.Extremely sensitive to heat
4.Mostly obsolete in today's commercial machining
5.It is still commonly found in non-intensive
6.Applications such as hobbyist or MRO machining, where
economy-grade drill bits, taps and dies, hacksaw blades and
reamers are still usually made of it (because of its affordability)
7.Hardness up to about HRC 65
8.Sharp cutting edges possible

1.Unstable
2.Inexpensive
High speed steel
3.Retains hardness at moderate temperatures
4.The most common cutting tool material used today
5.Used extensively on drill bits and taps

1.Unstable
HSS cobalt
2. Moderately expensive
3.The high cobalt versions of high speed steel are very resistant
to heat and thus excellent for machining abrasive and/or work
hardening materials such as titanium and stainless steel.
4.Used extensively on milling cutters and drill bits
6.Sharp cutting edges possible.

Cast cobalt alloys
1.Stable
2.Expensive
3.Somewhat fragile
4.Despite its stability it doesn't allow for high machining
speed due to low hardness. Not used much.

1.Stable
Cemented carbide
2.Moderately expensive
3.It is offered in several "grades" containing different proportions
of tungsten carbide and binder (usually cobalt)
4.High resistance to abrasion
5.High solubility in iron requires the additions of tantalum
carbide and niobium carbide for steel usage

6.Its main use is in turning tool bits although it is very common
in milling cutters and saw blades.
7.Hardness up to about HRC 90.
8.Sharp edges generally not recommended.

Ceramics
1.Stable
2.Moderately inexpensive
3.Chemically inert and extremely resistant to heat, ceramics are
usually desirable in high speed applications, the only drawback
being their high fragility
4. Ceramics are considered unpredictable under unfavorable
conditions

5. The most common ceramic materials are based on alumina
(Aluminium oxide), silicon nitride and silicon carbide
6.Used almost exclusively on turning tool bits
8.Sharp cutting edges and positive rake angles are to be avoided

Cermets
1.Stable
2.Moderately expensive
3.Another cemented material based on titanium carbide (TiC)
4.Binder is usually nickel
5.It provides higher abrasion resistance compared to tungsten carbide
at the expense of some toughness

6. More chemically inert
7. Extremely high resistance to abrasion
7.Used primarily on turning tool bits although research is being
carried on producing other cutting tools
9.Sharp edges generally not recommended.

1.Stable
2.Very Expensive
Diamond
3.The hardest substance known to date
4.Superior resistance to abrasion but also high chemical affinity to
iron which results in being unsuitable for steel machining.
6.Extremely fragile
7.Used almost exclusively on turning tool bits although it can be
used as a coating on many kinds of tools
8.Sharp edges generally not recommended

Question & Answer Session
Q1. What are different angles involved in single point tool
geometry?
Q2. What are different tool signature system ?
Q4. What are different cutting tool materials ?

Lecture 3 (MP-1)

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