4. Gradually there has been advancement in
cutting tool materials.
Stone Copper Bronze Iron
Carburised Iron(Steel) High Speed Steel
Sintered Hard Carbides UCON(Consisting
columbium,Tungsten and titanium)
Polycrystalline Diamond(PCD)
BORAZON(cubic Carbon Nitride(CCN)
Diamond
5. High or Low Precision and Cost
Volume Of Production
Type Of Machining Operations(Roughing or
Finishing, High Or Low speed)
TheTool design Details(Cutting and
Clearance angle, Method of Holding, Rigidity)
Physical Characteristics OfWork Material
6. Hot Hardness: It is the ability of the cutting tool to withstand
high temperature without losing its cutting edge.
Wear Resistance: It is the ability to resist wear.
Toughness:This property poses limitation on the Hardness
of the tool, because with high hardness, tool becomes brittle
and weak in tension.
Mechanical andThermal Shock resistance.
Low friction: In order to have low tool wear and better
surface finish, the coefficient between chip and cutting tool
should be as low as possible.
Favourable cost.
Should be easy to regrind and easily weldable to tool.
8. The chief Characteristics of carbon tool steels
are low hot hardness and poor hardenability.
They are limited in use to tools of small
section with operate at relatively at low
speed.
Composition: C=0.8 to 1.3%, Si= 0.1 to 0.4%,
Mn= 0.1% to 0.4%
9. For making tool Harder, Addition of carbon content
make tool Brittle.
Small amount of chromium and molybdenum are
used.
4%Tungsten is added to improve wear resistance. In
these type of materials, wear resistance is required.
They are used for drills,Taps and reamers.
10. The chief characteristics of HSS are superior hot hardness and wear
resistance.These can retain their cutting tool edge upto 600 degree
Celsius.
Cutting speeds are limited upto 0.75 to 1.8 m/s.
Typical CompositionOfW-MoType HSS
Type W Cr V Mo C Fe
HT 18 4 1 - 0.7 Balanc
e
HM 1.5 4 1 8.5 0.8 Balanc
e
TM 6 4 2 5 0.8 Balanc
e
11. A number of non-ferrous alloys high in cobalt have
been developed for use as cutting tools.
These materials can not be heat treated and are
used as cast at a temperature of about 1260 degree
Celsius.
These contain 40-50% cobalt, 27-32% chromium,
14-29% tungsten and 2-4% carbon.
12. The C-grade consisting of tungsten carbide with cobalt as a
binder, for use in machining cast iron and non-ferrous
metals. In the grade cobalt concentration is varied from 3-
16%.
The S-grade consisting of tungsten carbide, titanium carbide
and tantalum carbide with a cobalt binder for used in
machining tool.(Tantalum carbide: 0-10%,TiC:0-16%)
They have very high hardness for high range of temprature.
13. It is known as diamond is a hardest known material. It has
lowest thermal expansion (12% of that steel), high heat
conductivity (2 times that of steel), very low coefficient of
friction against metals and it is poor electrical conductor.
Synthetics polycrystalline diamonds are available as
mechanically clamped cutting tips.
The random orientation of their crystals gives them
improved impact resistance.
14. The performance of HSS tools can be enhanced by
coating ofTiN(Titanium Nitride) on HSS cutting tools.
It improves appearance of tool.
Metal removal rate can be doubled.
It reduces tool temperature and reduces adhesion wear
near the cutting edge.
After coating the hardness is 80-85 Rc, higher
Compared non-coated HSS whose hardness is 65-75Rc.
It possesses high chemical stability, being extremely
resistant to corrosion.
It retains all desirable properties at high temperature.
Encountered during machining.