Rockwell Hardness - ASTM D785
 |
Purchase and download the official ASTM D785 standard today! |
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.
Rockwell Hardness Test Parameters
| 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 |
| K |
10 |
150 |
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.
Similar Standards
|
