Which of the following is NOT a prime requirement of tool material?

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.