Out of the following cutting tools, the hardest one which is next to diamond is _______. 

This question was previously asked in
JKSSB JE Mechanical 02 Nov 2021 Shift 1 Official Paper
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  1. cubic boron nitride
  2. High Speed Steel 
  3. Ceramics
  4. Cemented carbide

Answer (Detailed Solution Below)

Option 1 : cubic boron nitride
Free
ST 1: JKSSB JE - Surveying
5.1 K Users
20 Questions 20 Marks 20 Mins

Detailed Solution

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Explanation:

The hardness of some common materials in the Knoop scale is shown in the table.

Material

Hardness (N/mm2)

Hardness Steel

7,000 – 13,000

Tungsten Carbide

18,000 – 24,000

Aluminium Oxide

20,000 – 30,000

Titanium Carbide

18,000 – 32,000

Silicon Carbide

21,000 – 30,000

Boron Carbide

28,000

Cubic Boron Nitride (CBN)

35,000 – 47,500

Diamond

70,000 – 80,000


Thus from the table hardness of the material next to the Diamond is Cubic Boron Nitride (CBN).

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