HomeTechnique & ApplicationA Minimum Thickness Guide for Selection of Scales Using the 1/16 in. (1.588 mm) Diameter Ball Indenter

A Minimum Thickness Guide for Selection of Scales Using the 1/16 in. (1.588 mm) Diameter Ball Indenter

For any given thickness, the indicated Rockwell hardness is the minimum value acceptable for testing. For a given hardness, material of any greater thickness than that corresponding to that hardness can be tested on the indicated scale.

Minimum Thickness Rockwell Superficial Scale
15T 30T 45T
in. mm Hardness Reading Approximate Hardness B-ScaleA Hardness Reading Approximate Hardness B-ScaleA Hardness Reading Approximate Hardness B-ScaleA
0.010 0.25 91 93 - - - -
0.012 0.30 86 78        
0.014 0.36 81 62 80 96    
0.016 0.41 75 44 72 84 71 99
0.018 0.46 68 24 64 71 62 90
0.020 0.51 - - 55 58 53 80
0.022 0.56 - - 45 43 43 70
0.024 0.61 - - 34 28 31 58
0.026 0.66 - - - - 18 45
0.028 0.71 - - - - 4 32
0.030 0.76 - - - -    

A These approximate hardness numbers are for use in selecting a suitable scale, and should not be used as hardness conversions. If necessary to convert test readings to another scale refer to Hardness Conversion Tables ASTM E 140 (Relationship Between Brinell Hardness, Vickers Hardness, Rockwell Hardness, Rockwell Superficial Hardness and Knoop Hardness).