51) Why is the head of a chisel not hardened ?
The chisel is not hardened all over. Its head is left soft as hardened head may damaged due to brittleness when resisting the hammer blow.
52) During forging what will happen if the metal is heated to:
(1) too low temperature (2) too high temperature
- When forging it is necessary to heat the metal to correct forging temperature. Heated in low temperature there is a risk for formation of cracks in the metal.
- If the metal is heated at too high temperature, the metal will loss its strength.
53) What is the function of hood in the forge ?
To collect gases through the fire and control the smoke and sparks.
54) Why new files should not be used on castings and forgings ?
Because they have hard outer surface, when new files are used on these over sides the teeth either break or get blunt easily.
55) For machining cast iron which rake angle is given on shaper tool ?
Negative rake angle
56) What is the material of shaper tool ?
Generally used HSS(High Speed Steel),sometimes satellite, carbide tipped tools may also be used.