Superficial Rockwell Hardness Test

The Superficial Rockwell hardness test method consists of indenting the test material with a diamond cone (N scale) or hardened steel ball indenter. The indenter is forced into the test material under a preliminary minor (29.43N)and the conditions are allowed to settle. Then the indicating device that follows the movements of the indenter is set to a datum position. An additional major load, is applied with resulting increase in penetration . The conditions are allowed to settle again and then the additional major load is removed. The permanent increase in depth of penetration, resulting from the application and removal of the additional major load is used to calculate the Rockwell Superficial hardness number.

HR = E - e

e = permanent increase in depth of penetration due to major load F1, measured in units of 0.001 mm
E = a constant of 100 units for diamond and ball indenters
HR = Rockwell hardness number
D = diameter of steel ball

Scale	Indenter	Major Load ( N )	E	Application
15N	120o Diamond cone	117.72	100	Similar to C scale, but for thin materials
30N	120o Diamond cone	264.87	100	Same as 15N
45N	120o Diamond cone	412	100	Same as 15N
15T	1/16" steel ball	117.72	100	Similar to B scale, but for thin materials
30T	1/16" steel ball	264.87	100	Same as 15T
45T	1/16" steel ball	412	100	Same as 15T
15W	1/8" steel ball	117.72	100	For very soft materials
30W	1/8" steel ball	264.87	100	For very soft materials
45W	1/8" steel ball	412	100	For very soft materials
15X	1/4" steel ball	117.72	100	For very soft materials
30X	1/4" steel ball	264.87	100	For very soft materials
45X	1/4" steel ball	412	100	For very soft materials
15Y	1/2" steel ball	117.72	100	For very soft materials
30Y	1/2" steel ball	264.87	100	For very soft materials
45Y	1/2" steel ball	412	100	For very soft materials