ABSTRACT

In the context of machining, a cutting tool (or cutter) is any tool that

is used to remove material from the work piece by means of shear

deformation. Cutting may be accomplished by single-point or multipoint

tools. Single-point tools are used in turning, shaping, plaining and similar

operations, and remove material by means of one cutting edge. Milling and

drilling tools are often multipoint tools. Grinding tools are also multipoint

tools. Each grain of abrasive functions as a microscopic single-point cutting

edge (although of high negative rake angle), and shears a tiny chip.

Cutting tools must be made of a material harder than the material

which is to be cut, and the tool must be able to withstand the heat

generated in the metal-cutting process. Also, the tool must have a specific

geometry, with clearance angles designed so that the cutting edge can

contact the workpiece without the rest of the tool dragging on the workpiece

surface. The angle of the cutting face is also important, as is the flute width,

number of flutes or teeth, and margin size. In order to have a long working

life, all of the above must be optimized, plus the speeds and feeds at which

the tool is run.

INTRODUCTIONOn a daily basis, individuals use cutting tools in everyday life, whether it is

knives, lawnmowers, to more industrial tools in plumbing, woodworking and

metalwork. At the same time, not too many people question how these helpful

and more-than-necessary tools came to life and even fewer know the history

of cutting tools. In the context of metal working, a cutting tool, or tool bit, is

used to remove metal from the work piece by shear deformation. Cutting tools

are also made of materials harder than the substance it will cut to withstand

the heat generated and have an increased tool life.

 

The history of cutting tools began during in the industrial revolution in 1800

A.D., but the first cutting took was cast using a crucible method in 1740. In

1868, R.Mushet discovered that adding Tungsten can increase hardness in

metals and increase tool life. Tungsten is a chemical element and a steel-gray

colored metal. It’s known for its robust physical properties and it has the

highest melting point of all non-alloyed metals and the second highest melting

point of all elements after carbon.

 

F.W. Taylor did the most basic research in metal cutting in Pennsylvania

between 1880 and 1905. Taylor was also able to invent a high speed steel and

better alloy to improve previous designs and techniques. In 1890, Tungsten

carbide was first synthesized and was used in Germany. 

 In 1980, the first collections of router tools were designed to slice and shear

instead of chop materials. In 1981, tool design became revolutionary and tools

were able to cut thick steel. In 1983, tools were first produced to cut plastic

materials. In 1986, the first production tools were designed to reduce wear

and hot corrosion through geometry and special carbide. In 2004, there was a

major introduction of unique tools to accommodate the growing use of

modern composite materials.

PROPERTIES OF CUTTING TOOL MATERIAL

The cutting tool materials must possess a number of important properties to

avoid excessive wear, fracture failure and high temperatures in cutting, The

following characteristics are essential for cutting materials to withstand the

heavy conditions of the cutting process and to produce high quality and

economical parts:

HARDNESS:

At elevated temperatures (so-called hot hardness) so that hardness and

strength of the tool edge are maintained in high cutting temperatures

TOUGHNESS:

Ability of the material to absorb energy without failing. Cutting if often

accompanied by impact forces especially if cutting is interrupted, and cutting

tool may fail very soon if it

is not strong enough.

WEAR RESISTANCE:

although there is a strong

correlation between hot

hardness and wear

resistance, later depends on

more than just hot

hardness. Other important

characteristics include

surface finish on the tool,

chemical inertness of the tool material with respect to the work material, and

thermal conductivity of the tool material, which affects the maximum value of

the cutting temperature at tool-chip interface.

TYPES OF CUTTING TOOL MATERIALS

Many types of tool materials, ranging from high carbon steel to ceramics and

diamonds, are used as cutting tools in today’s metalworking industry. It is

important to be aware that differences do exist among tool materials, what

these differences are, and the correct application for each type of material.

The various tool manufacturers assign many names and numbers to their

products. While many of these names and numbers may appear to be similar,

the applications of these tool materials may be entirely different. In most

cases, the tool manufacturers will provide tools made of the proper material

for each given application. In some particular applications, a premium or

higher priced material will be justified.

This does not mean that the most expensive tool is always the best tool.

Cutting tool users can’t afford to ignore the constant changes and

advancements that are being made in the field of tool material technology.

When a tool change is needed or anticipated, a performance comparison

should be made before selecting the tool for the job. The optimum tool is not

necessarily the least expensive or the most expensive, and it is not always the

same tool that was used for the job last time. The best tool is the one that has

been carefully chosen to get the job done quickly, efficiently, and

economically.

Cutting tool materials can be divided into two main categories: stable and

unstable.

Unstable materials (usually steels) are substances that start at a relatively low

hardness point and are then heat treated to promote the growth of hard

particles (usually carbides) inside the original matrix, which increases the

overall hardness of the material at the expense of some its original toughness.

Since heat is the mechanism to alter the structure of the substance and at the

same time the cutting action produces a lot of heat, such substances are

inherently unstable under machining conditions.

Stable materials (usually tungsten carbide) are substances that remain

relatively stable under the heat produced by most machining conditions, as

they don't attain their hardness through heat. They wear down due to

abrasion, but generally don't change their properties much during use.

Most stable materials are hard enough to break before flexing, which makes

them very fragile. To avoid chipping at the cutting edge, most tools made of

such materials are finished with a sightly blunt edge, which results in higher

cutting forces due to an increased shear area. Fragility combined with high

cutting forces results in most stable materials being unsuitable for use in

anything but large, heavy and stiff machinery.

Unstable materials, being generally softer and thus tougher, generally can

stand a bit of flexing without breaking, which makes them much more suitable

for unfavorable machining conditions, such as those encountered in hand

tools and light machinery.

The most used cutting tool materials are

1. Carbon tool steels

2. High speed steel(HSS)

3. HSS cobalt

4. Cast cobalt alloys

5. Cemented carbide

6. Ceramics

7. Cermets

8. Cubic boron nitride(CBN)

9. Diamond

CARBON TOOL STEELS

Tool steel refers to a variety of carbon and alloy steels that are particularly

well-suited to be made into tools. Their suitability comes from their

distinctive hardness, resistance to abrasion, their ability to hold a cutting

edge, and/or their resistance to deformation at elevated temperatures (red-

hardness). Tool steel is generally used in a heat-treated state. Many high

carbon tool steels are also more resistant to corrosion due to their higher

ratios of elements such as vanadium and niobium.

With a carbon content between 0.7% and

1.5%, tool steels are manufactured under

carefully controlled conditions to

produce the required quality. The

manganese content is often kept low to

minimize the possibility of cracking

during water quenching. However,

proper heat treating of these steels is important for adequate performance,

and there are many suppliers who provide tooling blanks intended for oil

quenching.

Tool steels are made to a number of grades for different applications. Choice

of grade depends on, among other things,

whether a keen cutting edge is necessary, as in

stamping dies, or whether the tool has to

withstand impact loading and service conditions

encountered with such hand tools

as axes, pickaxes, and quarrying implements. In

general, the edge temperature under expected

use is an important determinant of both

composition and required heat treatment. The higher carbon grades are

typically used for such applications as stamping dies, metal cutting tools, etc.

Tool steels are also used for special applications like injection

molding because the resistance to abrasion is an important criterion for a

mold that will be used to produce hundreds of thousands of parts.

The AISI-SAE grades of tool steel is the most common scale used to identify

various grades of tool steel. Individual alloys within a grade are given a

number; for example: A2, O1, etc.

HIGH-SPEED STEEL

High-speed steel (HSS or HS) is a subset of tool steels, commonly used intool

bits and cutting tools. It is often used in power-saw blades and drill bits. It is

superior to the older high-carbon steel tools used extensively through the

1940s in that it can withstand higher

temperatures without losing its temper

(hardness). This property allows HSS to cut

faster than high carbon steel, hence the

name high-speed steel. At room

temperature, in their generally

recommended heat treatment, HSS grades

generally display high hardness

(above HRC60) and abrasion resistance (generally linked

to tungsten and vanadium content often used in HSS) compared with

common carbon and tool steels.

High speed steels are alloys that gain their properties from either tungsten or

molybdenum, often with a combination of the two. They belong to the Fe–C–X

multi-component alloy system where

Xrepresents chromium, tungsten, molybdenum, vanadium, or cobalt. enerally,

the X component is present in excess of 7%, along with more than

0.60% carbon. The alloying element percentages do not alone bestow the

hardness-retaining properties; they also require appropriate high-

temperature heat treatment to become true HSS; see History above.

In the unified numbering system (UNS), tungsten-type grades (e.g. T1, T15)

are assigned numbers in the T120xx series, while molybdenum (e.g. M2, M48)

and intermediate types are T113xx. ASTM standards recognize 7 tungsten

types and 17 molybdenum types.

The addition of about 10% of tungsten and molybdenum in total maximises

efficiently the hardness and toughness of high

speed steels and maintains those properties at

the high temperatures generated when cutting

metals.

In general the basic composition of T1 HSS is

18% W, 4% Cr, 1% V, 0.7% C and rest Fe. Such HSS tool could machine (turn)

mild steel at speed only up to 20~30 m/min (which was quite substantial in

those days)

A sample of alloying compositions of common high speed steel grades (by %wt)

Grade C[8] Cr Mo W V Co Mn Si

T1 0.65–0.80 4.00 - 18 1 - 0.1–0.4 0.2–0.4

M2 0.95 4 5 6.0 2.0 - - -

M7 1.00 4 8.75 1.75 2.0 - - -

M36 0.94 4 5 6.0 2.0 8.0 - -

M42 1.10 3.75 9.5 1.5 1.15 8.0 - -

APPLICATIONS

The main use of high-speed steels continues to be in the manufacture of

various cutting tools: drills, taps, milling cutters, tool bits, gear cutters, saw

blades, planer and jointer blades, router bits, etc., although usage for punches

and dies is increasing.

High speed steels also found a market in fine hand tools where their relatively

good toughness at high hardness, coupled with high abrasion resistance, made

them suitable for low speed applications requiring a durable keen (sharp)

edge, such as files, chisels, hand plane blades, and high quality kitchen, pocket

knives, and swords.

HSS COBALT

Cobalt dissolves in iron (ferrite and austenite) and strengthens it whilst at the

same time imparting high temperature strength (temperature on cutting

surfaces can be 850°C) During solution heat treatment (to dissolve the

carbides), cobalt helps to resist grain growth so

that higher solution temperatures can be used

which ensures a higher percentage of carbides

being dissolved. Steels are quenched after

solution annealing and the structure is then

very hard martensite, plus the retained high

temperature phase austenite plus carbides

peppered throughout the structure.

Tempering will precipitate the ultrafine

carbides still in solution and maximum

hardness will be attained. Here, cobalt plays

another important role, in that it delays their

coalescence. This is important as it means that during cutting, the structure is

stable up to higher temperatures. Thus, cobalt-containing tool steels are

capable of retaining strength to higher temperatures

– They cut faster for longer.

Tools, however, are not longer as simple as they were. The surface can be

modified by coating – with TiN or TiC for example, put on by plasma or vapour

deposition. These coatings increase cutting life by large factors (4 or 5 times)

and do so even after regrinding.

CEMENTED CARBIDE

Cemented carbide, also called widia, is a hard material used in machining

tough materials such as carbon steel or stainless steel, as well as in situations

where other tools would wear away, such as high-quantity production runs.

Most of the time, carbide will leave a better finish on the part, and allow faster

machining. Carbide tools can also withstand higher temperatures than

standard high speed steel tools.

COMPOSITION

Cemented carbides are composed of a metal matrix composite where carbide

particles act as the aggregate and a metallic binder serves as the matrix. The

process of combining the carbide particles with the binder is referred to

as sintering or Hot Isostatic Pressing (HIP). During this process the binder

eventually will be entering the liquid

stage and carbide grains (much higher

melting point) remain in the solid

stage. As a result of this process the

binder is embedding/cementing the

carbide grains and thereby creates the

metal matrix composite with its

distinct material properties. The naturally ductile metal binder serves to offset

the

characteristic brittle behavior of the carbide ceramic, thus raising its

toughness and durability. Such parameters of carbide can be changed

significantly within the carbide manufacturer's sphere of influence, primarily

determined by grain size, cobalt content, dotation (e.g. alloy carbides) and

carbon content.

The first Cemented Carbide developed was Tungsten Carbide (introduced in

1927) which uses tungsten carbide particles held together by a cobalt metal

binder. Since then other cemented carbides have been developed such as

Titanium-Carbide which is better suited for cutting steel and Tantalum-

Carbide which is tougher than Tungsten-Carbide.

APPLICATIONS

Carbide is more expensive per unit than other typical tool materials, and it is

more brittle, making it susceptible to chipping and breaking. To offset these

problems, the carbide cutting tip itself is often in the form of a small insert for

a larger tipped toolwhose shank is made of another material,usually

carbon tool steel. This gives the benefit of

using carbide at the cutting interface

without the high cost and brittleness of

making the entire tool out of carbide.

Most modern face mills use carbide

inserts, as well as many lathe tools

and endmills. In recent decades, though,

solid-carbide endmills have also become

more commonly used, wherever the application's characteristics make the

pros (such as shorter cycle times) outweigh the cons (mentioned above).

CERAMIC CUTTING TOOLS

Ceramic cutting tools are harder and more heat-resistant than carbides, but

more brittle. They are well suited for machining cast iron, hard steels, and the

super alloys. Two types of ceramic cutting tools are available: the alumina-

based and the silicon nitride-based ceramics. The alumina-based ceramics are

used for high speed semi- and final-finishing of ferrous and some non-ferrous

materials. The silicon nitride-based ceramics are generally used for rougher

and heavier machining of cast

iron and the super alloys.

Ceramic materials are composed

primarily of fine-grained, high-

purity aluminum oxide (Al2O3),

pressed and sintered with no

binder. Two types are available:

1. ΠWhite, or cold-pressed ceramics, which consists of only Al2O3 cold

pressed into inserts and sintered at high temperature.

2. � Black, or hot-pressed ceramics, commonly known as cermet (from

ceramics and metal).

This material consists of 70% Al2O3 and 30% TiC.

Both materials have very high wear resistance but low toughness, therefore

they are suitable only for continuous operations such as finishing turning of

cast iron and steel at very high speeds. There is no occurrence of built-up

edge, and coolants are not required.

CUBIC BORON NITRIDE

Cubic boron nitride (CBN or c-BN) is widely used as an abrasive. Its usefulness arises from its insolubility in iron, nickel,

and related alloys at high temperatures, whereas diamond is soluble in these metals to give carbides. Polycrystalline c-BN (PCBN) abrasives are therefore used for machining steel, whereas diamond abrasives are preferred for aluminum alloys, ceramics, and stone. When in contact with oxygen at high temperatures, BN forms a passivation layer of boron oxide. Boron nitride binds well with metals, due to formation of interlayer’s of metal borides or nitrides. Materials with cubic boron nitride crystals are often used in the tool bits of cutting tools. For grinding applications, softer binders, e.g. resin, porous ceramics, and soft metals, are used. Ceramic binders can be used as well. Commercial products are known under names "Borazon" (by Diamond Innovations), and "Elbor" or "Cubonite" (by Russian vendors). Similar to diamond, the combination in c-BN of highest thermal conductivity and electrical resistivity is ideal for heat spreaders. Contrary to diamond, large c-BN pellets can be produced in a simple process (called sintering) of annealing c-BN powders in nitrogen flow at temperatures slightly below the BN decomposition temperature. This ability of c-BN and h-BN powders to fuse allows cheap production of large BN parts.

As cubic boron nitride consists of light atoms and is very robust chemically

and mechanically, it is one of the popular materials for X-ray membranes: low

mass results in small X-ray absorption, and good mechanical properties allow

usage of thin membranes, thus further reducing the absorption.

CONCLUSIONS

Machining is now in a particular “golden age”, where a lot of time, money and

effort has been invested to define the best tool for each application. Today for

each application the objective of large or small manufacturers is to supply a

much optimized tool, in all the related aspects discussed in this chapter. One

of the most important aspects for the success of the new cutting tools is the

application guide, because each application needs special recommendations,

and in some cases they are contradictory to others.

Tools specially designed for multitasking machining .The second from the

right side is a mini-turret. The economical impact of cutting and machining is

increasing, although the near to net shape technologies imply a reduction of

the amount of material to be removed in each part. But the demand for

elaborate parts and high-end products exceeds all expectations. Consequently

the improvement of productivity, tool life and workpiece precision is a main

goal for a lot of companies, taking into account respect for the environment as

well.

Micromilling is going to be a growing technology where hard milling is going

to be applied , with special attention to medical devices. a test part used to

study micromilling is presented. Tool fabrication is another important issue

for the application of micromilling technology. For industrial applications,

micropowder (0.3 m particle size) sintered tungsten carbide is used, makingμ

two flute endmills of 100 m in diameter, with an edge radius of 1–2 m. Inμ μ

any case, the commercial offer is limited and there are no different geometries

for different materials, being an important problem because most of the tools

are designed for steel machining. Commercial tools have a well-defined

geometry with small tolerances.

Tolerance indicated in the catalogues for the sum of geometrical error

plus runout error is of ±10 m. However, real errors are usually smaller (±5μ

m), but even in the best case, the tolerance with respect to size of the form toμ

be machined is poor if compared to conventional high-speed machining mills.

Tool wear is rapid and has a considerable effect on the process performance.

On the other hand, materials with improved mechanical features are now in

development,with more tensile strength and creep resistance. New alloys are

usually very low-machinability alloys, asking for recommendation to be

machined. Some examples are austempered ductile irons for car components

and wind-energy gearboxes, gamma TiAl for car components and

aeronautical engines, highsilicon aluminium alloys, carbon-fibre-reinforced

plastic composites , and others. Special tools will soon be on the market to

solve the problems derived from the applications of these very difficult-to-cut

materials.

INTRODUCTION

PROPERTIES OF CUTTING MATERIAL

DESIGN OF LASER

TYPES OF CUTTING TOOL MATERIALS

CARBON TOOL STEELS

HIGH SPEED STEEL(HSS)

HSS COBALT

CAST COBALT ALLOYS

CEMENTED CARBIDE

CERAMICS

CERMETS

CUBIC BORON NITRIDE(CBN)

CONCLUSIONS

ER. ASIT KUMAR SAHOO

&

ER. ABHIJIT MOHANTY

We wish to convey our hearty thanks to Er. Abhijit Mohanty for having provide

all the to complete the seminar successfully and also our special thanks to our H.O.D.

Er. Asit Kumar Sahoo.

We would like to register our special thanks to the staff members of Mech. Engg.

Department for their kind co-operation and at every state directly or indirectly to

bring out the work successfully.

Finally, we feel pleasure to register our gratitude with deep feeling and sense of

honor to my parents who were kind enough to encourage us to study in the field of

MECH. ENGG. and support extend financially and physically to complete my studies

successfully .

Group -5, 4th Semester, Mech. Engg.

MAHALAXMI INSTITUTE OF TECHNOLOGY & ENGINEERINGRAJNILGIRIBALASORE

2014

This is to certify that the seminar report entitled “CUTTING TOOLS AND MATERIALS” submitted by the following students Of MAHALAXMI INSTITUTE OF TECHNOLOGY & ENGINEERING, in partial fulfillment of the requirement for the DIPLOMA in 4th Semester Mech. Engineering is a record of seminar presented by him under my own guidance & supervision in MAHALAXMI INSTITUTE OF TECHNOLOGY & ENGINEERING.

NAME OF THE STUDENTS CLASS ROLL NOJYOTI RANJAN NAYAK 61RAKESH MAR MOHANTA 62ALOK KUMAR GIRI 63SAROJ KUMAT MOHAPATRA 64SATYAPRAKASH DAS 65SATYAJIT PANDA 66SUBASHISH SETHI 67SUBRAT KUMAR NAYAK 68BIKASH MALLICK 69MUKTIKANTA MISHRA 70UMAKANTA SAHOO 71JYOTI RANJAN PANDA 72NIRANJAN PRUSTI 73BALARAM CHAND 74BIDYADHAR SAHOO 75

They have taken interest in presenting this seminar.Remark: We wish them bright and successful future.

group-5 , 4th Semester, Mech. Engg.MAHALAXMI INSTITUTE OF TECHNOLOGY & ENGINEERING

RAJNILGIRI2014

ER. ASIT KUMAR SAHOOH.O.D.

Mahalaxmi Institute of technology & EngineeringBalasore

ER. ABHIJIT MOHANTYLect. In Mechanical Department

Mahalaxmi Institute of Technology & EngineeringBalasore