Rockwell Scale

The Rockwell scale is a scale to measure hardness.  The scale is based on the depth of the indentation produced on a material.  The test works by using an indentor to makes an indentation.

The Rockwell test is a non-destructive testing.  Its setup is easy to install.

The indentation hardness is linearly related to tensile strength.  Thiss permits the quick and reliable testing of bulk materials. 

The test
A minor load is placed on the specimen.  The depth of the indentation formed is noted.  This is the zero point.  A bigger load, called the major load, is now placed upon the minor load.  The depth of the indentation with reference to the zeropoint is noted. 

The depth of indentation and the hardness are inversely related.  A hard material will have lesser depth of indentation while a softer material will have a greater depth of indentation. 

The hardness of a material can be directly calculated from the formula

HR= N- d/s

where N is the Rockwell scale used and s is the scale factor