Scope:

Rockness hardness ASTM D785 test method includes two different procedures for testing the indentation hardness of plastics and plastic-related electrical insulating materials using the Rockwell hardness tester. The Rockwell Hardness Test is a hardness calculation that is dependent on the net increase in depth of impact when a load is applied. Hardness numbers have no units and are generally given in the R, L, M, E, and K scales. Higher numbers mean tougher materials.

Test Procedure:

A typical sample is positioned on the Rockwell Hardness Tester’s surface. The gauge is reset to zero after a small load is applied. The primary force is exerted by tripping a lever. The main load is withdrawn after 15 seconds. After allowing the sample to recover for 15 seconds, the hardness value is read off the tester dial while a slight load is still applied.

Specimen size:

A standard sample for the Rockwell Hardness test is 6.4 mm (0.25 inches) thickness that is either molded or cut from a sheet.

Data:

The different hardness value is visually recorded directly from the dial with suitable R, L, M, E or K scales. The tougher the object, the higher the number on each scale. Plastics are often measured using R and M scales.