The Superficial Rockwell method employs the same penetrators of the Standard Rockwell.
The diamond indenter, however, although having the same profile, requires more a higher accuracy of the angle and of the radius. In fact, light loads give a little indentation, and in case the diamond point is not perfect, the results will be wrong.
Preload is constant: 3 kgf (29.43N).
Loads (preload + additional load) can be: 15, 30, 45 kgf (147.1, 294.2, 441.3 N). The unit of measurement of the Superficial Rockwell method corresponds to 0.001 mm penetration.
In the Superficial Rockwell test the zero setting is made at 100 (0 dial indicator), whether when using a diamond indenter or a ball penetrator. In fact, dial indicators are divided into 100 graduations, where a revolution corresponds in this case to 0.1 mm.
With a diamond or ball indenter and 0.082 mm penetration, the hardness will be given by: 100-82= 18 Superficial Rockwell.
The test load followed by a letter, as shown in table 2, indicates the superficial Rockwell scales.
The hardness number is placed before this abbreviation, for example 65 HR30 T.