Question

Which of the following is NOT a prime requirement of tool material?
1. It should have good machinability
2. It should have low melting point
3. It should have low erosion rate
4. None of the options

Answer 1

Correct Answer - Option 2 : It should have low melting point

Explanation:

Cutting tool materials should be:

• harder and stronger than the material being cut
• tough to resist shock loads
• resistant to abrasion thus contributing to long tool life
• should have low erosion rate
• should have good machinability

Cutting tool material should possess the following qualities:

• Cold hardness
• Red hardness
• Toughness

Cold hardness

• It is the amount of hardness possessed by a material at normal temperature.
• Hardness is the property by which it can cut/scratch other metals.
• When hardness increases, brittleness also increases, and a material, which has too much of cold hardness, is not suitable for the manufacture of cutting tools.

Red hardness

• It is the ability of a tool material to retain most of its cold hardness property even at very high temperatures.
• While machining, the friction between the tool and the work causes heat to be generated, and the tool loses its hardness, and its efficiency to cut diminishes.
• If a tool maintains its cutting efficiency even at increased temperatures during cutting, it can be said that it possesses the red hardness property.

Toughness

• The property to resist breakage due to sudden load that results during metal cutting is termed as 'toughness'.
• This will reduce the breakage of the cutting edges of tools.