Rockwell Hardness - ISO 2039-2
Rockwell hardness is a measure of the indentation resistance of a material. Testing is performed by first forcing a steel ball indentor into the surface of a material using a specified minor load. The load is then increased to a specified major load and then decreased back to the original minor load. Rockwell hardness is a measure of the net increase in depth of the indentor. Each Rockwell scale division represents a 0.002 mm (0.00008 in) penetration of the indentor.
Scale | Minor Load (kg) | Major Load (kg) | Indentor Diameter (in) | Indentor Diameter (mm) |
---|---|---|---|---|
R | 10 | 60 | 0.5 | 12.7 |
L | 10 | 60 | 0.25 | 6.35 |
M | 10 | 100 | 0.25 | 6.35 |
E | 10 | 100 | 0.125 | 3.175 |
Rockwell hardness is calculated by subtracting the penetration divided by the scale division from 130. For example, if the indentor has a net depth increase of 0.12mm, the Rockwell hardness is
70.
Hardness = 130 - (penetration / scale division)
Hardness = 130 - (0.12mm / 0.002mm) = 70
Shown below is a hardness comparison chart. Hardness is a complex material property influenced by a variety of factors. Any conversions using this chart will be a rough estimate and should not
be considered an exact conversion.