BALL HARDNESS CORRECTIONS FOR CURATURES
The table below is useful for converting Rockwell 'C' scale readings taken on ball surface es to equivalent value applicable to flat surfaces. Hardness reading of balls are affected by the curvature and hardness level of the ball. Because of these factors, corrections are necessarily added to the as-read hardness. For ball size and hardness values shall be interpolated.

BALL
DIAMETERS
ROCKWELL 'C' READINGS
mm 55 56 57 58 59 60 61 62 63 64 65
3.175 6.1 5.7 5.4 5.1 4.8 4.5 4.2 4.0 3.8 3.6 3.4
3.968 5.6 5.3 5.0 4.7 4.4 4.1 3.8 3.6 3.4 3.2 3.0
4.762 5.1 4.7 4.3 4.0 3.8 3.6 3.4 3.2 3.0 2.8 2.5
5.562 4.6 4.3 4.0 3.7 3.5 3.3 3.1 2.9 2.7 2.5 2.3
6.350 4.1 3.8 3.6 3.3 3.1 2.9 2.7 2.5 2.3 2.1 1.8
7 3.7 3.4 3.2 3.0 2.8 2.6 2.4 2.2 2.0 1.8 16
7.938 3.1 2.9 2.7 2.6 2.4 2.2 2.0 1.9 1.7 1.5 1.3
8 3.1 2.9 2.7 2.6 2.4 2.2 2.0 1.5 1.7 1.5 1.3
9 2.7 2.5 2.4 2.2 2.0 1.9 1.7 1.4 1.4 1.2 1.1
9.525 2.5 2.3 2.2 2.0 1.9 1.8 1.6 1.3 1.2 1.1 1.0
10 2.4 2.2 2.0 1.9 1.8 1.7 1.5 1.1 1.1 1.0 0.9
11 2.1 2.0 1.8 1.5 1.6 1.5 1.3 1.0 0.9 0.8 0.7
12 1.9 1.7 1.6 1.5 1.4 1.3 1.1 0.9 0.8 0.7 0.6
12.700 1.8 1.7 1.6 1.5 1.4 1.2 1.0 0.9 0.7 0.6 0.5
13 1.8 1.7 1.6 1.5 1.4 1.2 1.0 0.8 0.7 0.6 0.5
14 1.6 1.5 1.4 1.3 1.2 1.0 0.9 0.7 0.6 0.5 0.4
15 1.5 1.4 1.3 1.2 1.1 0.9 0.8 0.7 0.5 0.4 0.3
15.875 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.5 0.4 0.3
16 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.6 0.5 0.4 0.3
17 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.5 0.4 0.3 0.2
18 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2
19 1.1 1.0 0.9 0.8 0.7 0.7 0.6 0.5 0.4 0.3 0.2
19.050 1.1 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2
20 1.0 1.0 0.9 0.8 0.8 0.7 0.6 0.5 0.4 0.3 0.2
25.400 0.8 0.8 0.7 0.6 0.5 0.4 0.4 0.3 0.3 0.2 0.1

 



  

Important Links:

Grades of balls

   No of Balls per /Kg

Burnishing Applications I.S. 2898 (INDIA),I.S.O. 3290 Standard, G.B 308 (G.B)
  How Balls  are made ANSI/AFBMA- (USA),  
    AFNOR NF E 22-381 - (FRANCE)
    DIN 5401 (GERMANY)


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