Type of Cutting Tools
There are two types of cutting tools.
i ) Single Point Cutting Tools
ii) Multiple Point Cutting Tools.
i) Single Point Cutting Tools :-
The tools which make use of a single sharp cutting edge to remove deformities are known as Single Point Cutting Tools.
It can be used to increase the size of holes i.e boring. It is also used in turning which is exact opposite of turning.
ii) Multiple Point Cutting Tools:-
The tools which make use of multiple cutting edge is called multiple point cutting tools. This tool is mounted on a machine and used by rotating this tool. This tools are used for drilling and mining.
Cutting tools are also classified on the basis of the types of material used in their cutting edge.
Based on the types of materials used cutting tools are divided into following types :-
1) Carbon Tool Steel
2) High Speed Steel
3) Cemented Carbide
4) Ceramics Tools
5) Cubic boron nitride Tool
6) Diamond Tool
1) Carbon Steel Tool :-
Carbon Steel is a steel with carbon content up to 2.1% by weight. It is very inexpensive tool used for the low-speed machining operation. Other metals like Cr,V are added to it to change the hardness and grain size.
This material loses hardness at temperature near 250 C. Therefore these can’t be used at high temperature .Carbon Steel tools have a hardness of about 62 RC and usually opted for working with wood. This tool is not preferred in modern machine operation.
Carbon Steel tool is used in twist drills, milling , turning and forming of soft materials such as brass, aluminium, magnesium etc.
2) High Speed Steel :-
HSS has a higher resistance and hardness than Carbon Steel . Tool of high speed steel can cut metal at a speed more than 2 to 3 times faster than Carbon Steel Tools.
The melting point of this steel is about 900 C . Since it has high melting points , it can be used in operations which are done at high temperature.
High Speed is used for cuts on metals using different machines and processes.
3) Carbides :-
Carides have hot hardness over various temperature, high Young’s Modulus and high thermal conductivity . So, it is a good material for manufacturing cutting tools.
Carbides are made of Tungsten powder and carbon, mixed in a ratio of 94:6.
Hardness of cemented carbides is at level between diamond and saphire and weight is nearly twice of iron. After that it is sintered with cobalt at high temperature. Additional cobalt is provided to increase hardness.
A high cobalt tool is used for a rough cut while low cobalt tool is used for finishing operations.
Cemented carbides are very hard and can withstand very high speed cutting operation.
These tools does not loose hardness up to 1000 C.
4) Cast Cobalt Alloys :-
Cast Cobalt alloys have compositions of about 40-50% cobalt, 30 % chromium and 10-20% tungsten. These alloys are not heat treatable.
Cast Cobalt Alloys have maximum hardness value of 55-64 Rc. They have good wear resistance but less tough than High Speed Steel.
Cast Cobalt alloys maintain their hardness from upto 760 C. The tools made from Cast Cobalt Alloys are very less used in today’s world.
5) Ceramics tools:-
A ceramic is an inorganic non metalic solid made up of their metal or non-metal compounds that have been shaped and then hardened by heating at high temperatures.
Most commonly ceramics tools are made by sintering Boron Nitride in powder form and Aluminium Oxide at very high temperature nearly 1700 C.
Ceramics have high compressive strength and are stable upto temperature 1800 C. The friction between the tool and chip is very less and possess low heat conductivity and hence no coolant is required.
Ceramics tools provide excellent surface finish.
They can be used in very high speed nearly 500 m/min and are used for continuous cutting only.
6) Cubic Boron Nitride Cutting Tools :-
After diamond, it is the hardest material.It consists of atoms of Nitrogen and Boron and produced by metallurgy process.
They are generally used in hand machines . They provide excellent surface finish. They offer high resistance to abrasion and are also used as abrasive wheels.
7) Diamond :-
It is hardest material known and is very expensive too. It is the hardest among the cutting tool. It has very high thermal conductivity and melting point.
Diamond also has excellent abrasion resistance, low friction coefficient and low thermal expansion . As diamond is a very hard cutting tools ,so it can be used to cut hard objects. It is used to cut hard materials such as carbides, glass, nitrides etc. Diamond is not good for cutting steel.
Diamonds are very expensive and are hence not used for cutting purposes. They are only used in specific industries and cutting very hard materials.