Roundness Correction Chart for Hardness Testing

Corrections to be added to test results in the following scales for various diameter parts

Corrections to be added to Rockwell C, A, and D values

Hardness   Diameter of Convex Cylindrical Surfaces    
Reading 1/4 in 3/8 in 1/2 in 5/8 in 3/4 in 7/8 in 1 in 1-1/4 in 1-1/2 in
  6.4 mm 10 mm 13 mm 16 mm 19 mm 22 mm 25 mm 32 mm 38 mm
20 6.0 4.5 3.5 2.5 2.0 1.5 1.5 1.0 1.0
25 5.5 4.0 3.0 2.5 2.0 1.5 1.0 1.0 1.0
30 5.0 3.5 2.5 2.0 1.5 1.0 1.0 1.0 0.5
35 4.0 3.0 2.0 1.5 1.5 1.0 1.0 0.5 0.5
40 3.5 2.5 2.0 1.5 1.0 1.0 1.0 0.5 0.5
45 3.0 2.0 1.5 1.0 1.0 1.0 0.5 0.5 0.5
50 2.5 2.0 1.5 1.0 1.0 0.5 0.5 0.5 0.5
55 2.0 1.5 1.0 1.0 0.5 0.5 0.5 0.5 0
60 1.5 1.0 1.0 0.5 0.5 0.5 0.5 0 0
65 1.5 1.0 1.0 0.5 0.5 0.5 0.5 0 0
70 1.0 1.0 0.5 0.5 0.5 0.5 0.5 0 0
75 1.0 0.5 0.5 0.5 0.5 0.5 0 0 0
80 0.5 0.5 0.5 0.5 0.5 0 0 0 0
85 0.5 0.5 0.5 0 0 0 0 0 0
90 0.5 0 0 0 0 0 0 0 0
                   
Corrections to be added to Rockwell B, F, and G values
Hardness   Diameters of Convex Cylindrical Surfaces    
Reading 1/4 in 3/8 in 1/2 in 5/8 in 3/4 in 7/8 in 1 in    
  6.4 mm 10mm 13mm 16 mm 19 mm 22 mm 25 mm    
                   
0 12.5 8.5 6.5 5.5 4.5 3.5 3.0    
10 12.0 8.0 6.0 5.0 4.0 3.5 3.0    
20 11.0 7.5 5.5 4.5 4.0 3.5 3.0    
30 10.0 6.5 5.0 4.5 3.5 3.0 2.5    
40 9.0 6.0 4.5 4.0 3.0 2.5 2.5    
50 8.0 5.5 4.0 3.5 3.0 2.5 2.0    
60 7.0 5.0 3.5 3.0 2.5 2.0 2.0    
70 6.0 4.0 3.0 2.5 2.0 2.0 1.5    
80 5.0 3.5 2.5 2.0 1.5 1.5 1.5    
90 4.0 3.0 2.0 1.5 1.5 1.5 1.0    
100 3.5 2.5 1.5 1.5 1.0 1.0 0.5    

When testing cylindrical specimens, the accuracy of the test will be seriously affected by alignment of elevating screw, Vee-anvil, indenters, surface finish, and the straightness of the cylinder. These corrections are approximate only and represent the averages, to the nearest 0.5. Rockwell and Rockwell superficial numbers, of numerous actual observations.
The above tables are from ASTM E 18
Reprinted from the Annual Book of STM Standards, copyright American Society for Testing and Materials.