Establishment of Brinell Hardness Scale at NPL India

Material hardness evaluation is one of the most important and commonly used methods of material or product testing. However, the hardness measurements being done in the industry are of limited accuracy due primarily to non-availability of standard hardness blocks having very precise and accurately assigned hardness values traceable to national primary standard. The National Physical Laboratory has recently added the primary standard of Brinell hardness scale to the other already available Vickers and Rockwell hardness primary standards. The uncertainty of the Brinell hardness standard is within ±1.5% for HB1/1 to HB1/30 and is within ±1.0% for other HB scales, which is reaffirmed through comparison with precision hardness standard blocks. Some of the salient features of the machine are described and the measurement results obtained on standard hardness blocks are reported.