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How to Measure the Scale of Hardness

There are a few scales of hardness in materials science, including the Mohs scale and the absolute hardness scale. Different materials find their place on the scales by what materials can scratch them, and by what materials they can scratch. The type of measurement techniques can yield different measures of hardness, as a small sample of a heterogeneous material is not necessarily representative of the bulk of that material. Nano-indentation methods are used to sample the hardness of a sample by applying a very small force and measuring the indentation.

Things You'll Need

Rockwell tester
Test material

Instructions

- 1
  Set the material to be tested in a Rockwell testing device.
- 2
  Apply the minor load. This is a small load, usually 10 kg, that is applied via a small steel ball or diamond cone used to make an impression in the material. This impression will serve as a seat for the major load.
- 3
  Apply the major load once the minor load has been lifted from the sample. This is a 100 kg load with the same steel ball, or up to 150 kg with the diamond tip.
- 4
  Measure the difference between the indentations of the major load and the minor load. This will give you a hardness rating on the Rockwell scale. There are no units on this scale.

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