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1A) usually 10 kgf. 1C).

The Rockwell hardness test method consists of indenting the test material with a diamond
cone or hardened steel ball indenter. The indenter is forced into the test material under a
preliminary minor load 𝐹0 (Fig. 1A) usually 10 kgf. When equilibrium has been reached, an
indicating device, which follows the movements of the indenter and so responds to changes in
depth of penetration of the indenter is set to a datum position. While the preliminary minor
load is still applied an additional major load is applied with resulting increase in penetration
(Fig. 1B). When equilibrium has again been reach, the additional major load is removed but
the preliminary minor load is still maintained. Removal of the additional major load allows a
partial recovery, so reducing the depth of penetration (Fig. 1C). The permanent increase in
depth of penetration, resulting from the application and removal of the additional major load
is used to calculate the Rockwell hardness number. There are several considerations for Rockwell hardness test

• Require clean and well positioned indenter and anvil


• The test sample should be clean, dry, smooth and oxide-free surface


• The surface should be flat and perpendicular to the indenter Low reading of hardness value might be expected in cylindrical surfaces


• Specimen thickness should be 10 times higher than the depth of the indenter


• The spacing between the indentations should be 3 to 5 times of the indentation diameter


• Loading speed should be standardized.