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Hardness Conversion Chart

Tensile Strength (N/mm2) Hardness Vickers Hardness Brinell* HRB HRF HRC HRA
770 240 228 98.1 114.3 20.3 60.7
785 245 233 21.3 61.2
800 250 238 99.5 115.1 22.2 61.6
820 255 242 23.1 62.0
835 260 247 (101) 24.0 62.4
850 265 252 25.8 62.7
865 270 257 (102) 25.8 63.1
880 275 261 26.4 63.5
900 208 266 (104) 27.1 63.8
915 285 271 27.8 64.2
930 290 276 (105) 28.5 64.5
950 295 280 29.2 64.8
965 300 285 29.8 65.2
995 310 295 31.0 65.8
1030 320 304 32.2 66.4
1060 330 314 33.3 67.0
1095 340 323 34.4 67.6
1125 350 333 35.5 68.1
1155 360 342 36.6 68.7
1190 370 352 37.7 69.2
1220 380 361 38.8 69.8
1255 390 371 39.8 70.3
1290 400 380 40.8 70.8
1320 410 390 41.8 71.4
1350 420 399 42.7 71.8
1385 430 409 43.6 72.3
1420 440 418 44.5 72.8
1455 450 428 45.3 73.3
1485 460 437 46.1 73.6
1520 470 447 46.9 74.1
1555 480 (456) 47.7 74.5
1595 490 (466) 48.4 74.8
1630 500 (475) 49.1 75.3
1665 510 (485) 49.8 75.7
1700 520 (494) 50.5 76.1
1740 530 (504) 51.1 76.4
1775 540 (513) 51.7 76.7
1810 550 (523) 52.3 77.0
1845 560 (532) 53.0 77.4
1880 570 (542) 53.6 77.8
1920 580 (551) 54.1 78.0
1955 590 (561) 54.7 78.4
1995 600 (570) 55.2 78.6
2030 610 (580) 55.7 78.9
2070 620 (589) 56.3 79.2
2105 630 (599) 56.5 79.5
2145 640 (608) 57.3 79.8
2180 650 (618) 58.7 80.0
660 58.3 80.3
670 58.8 80.6
680 59.2 80.8
690 59.7 81.1
700 60.1 81.3
720 61.0 81.8
740 61.8 82.2
760 62.5 82.6
780 63.3 83.0
800 64.0 83.4
820 64.7 83.8
840 65.3 84.1
860 65.9 84.4
880 66.4 84.7
900 67.0 85.0
920 67.5 85.3
940 68.8 85.6

* calculate from HB = 0.95 x HV

 

Ball Hardness Corrections for Curvatures

Ball Dia 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
7.000 3.7 3.4 3.2 3.0 2.8 2.6 2.4 2.2 2.0 1.8 1.6
7.938 3.1 2.9 2.7 2.6 2.4 2.2 2.0 1.9 1.7 1.5 1.3
8.000 3.1 2.9 2.7 2.6 2.4 2.2 2.0 1.9 1.7 1.5 1.3
9.000 2.7 2.5 2.4 2.2 2.0 1.9 1.7 1.5 1.4 1.2 1.1
9.525 2.5 2.3 2.2 2.0 1.9 1.8 1.6 1.4 1.2 1.1 1.0
10.000 2.4 2.2 2.0 1.9 1.8 1.7 1.5 1.3 1.1 1.0 0.9
11.000 2.1 2.0 1.8 1.7 1.6 1.5 1.3 1.1 0.9 0.8 0.7
12.000 1.9 1.7 1.6 1.5 1.4 1.3 1.1 1.0 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
13.000 1.8 1.7 1.6 1.5 1.4 1.2 1.0 0.9 0.7 0.6 0.5
14.000 1.6 1.5 1.4 1.3 1.2 1.0 0.9 0.8 0.6 0.5 0.4
15.000 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

This table is useful for converting Rockwell 'C' readings taken on ball surfaces to equivalent value applicable to flat surfaces. Hardness readings 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 sizes and hardness values other than shown, values shall be interpolated.