Rockwell Hardness Conversions
The Rockwell hardness scale is based on a material’s ability to resist permanent deformation. The Rockwell hardness test determines how hard a material is by measuring the depth of penetration of an prescribed indenter under a high load (kgf or "kilograms of force") compared to the penetration made by a preload. Hardness is a characteristic of bearing materials used in ball bearings, roller bearings, and bushings (plain bearings) whether they are made of metals, ceramics, plastics, or composite materials.
Rockwell Hardness Scales
There are different Rockwell scales, each denoted by a single letter, that are based upon different loads and indenters giving a dimensionless number noted as HRX, where X is the scale letter. The appropriate Rockwell scale used depends on the material being tested. Of the 7 Rockwell scales (A-G), the A, B, and C scales are used most frequently. However, the Rockwell C scale is typically used when measuring bearing material hardness.
|
Scale |
Abbr. |
Load |
Indenter |
Typical Use |
|
A |
HRA |
60 kgf |
120° diamond cone |
Tungsten Carbide Steel |
|
B |
HRB |
100 kgf |
1⁄16 inch diameter steel sphere |
Soft Steels, Brass, and Aluminum |
|
C |
HRC |
150 kgf |
120° diamond cone |
Harder steels |
Rockwell Hardness Conversion Table
Below is a conversion table for various hardness standards. Bearings are typically measured using the Rockwell C scale and are the primary reference in the first column. Conversions are approximate and in the case of numbers in parenthesis (), they are provided for reference only.
|
Rockwell |
Vickers | Rockwell | Brinell | Shore | ||
| A Scale (588.4N) | B Scale (980.7N) | Standard ball | Tungsten Carbide Ball | |||
| 68 | 940 | 85.6 | – | – | – | 97 |
| 67 | 900 | 85.0 | – | – | – | 95 |
| 66 | 865 | 84.5 | – | – | – | 92 |
| 65 | 832 | 83.9 | – | – | (739) | 91 |
| 64 | 800 | 83.4 | – | – | (722) | 88 |
| 63 | 772 | 82.8 | – | – | (705) | 87 |
| 62 | 746 | 82.3 | – | – | (688) | 85 |
| 61 | 720 | 81.8 | – | – | (670) | 83 |
| 60 | 697 | 81.2 | – | – | (654) | 91 |
| 59 | 674 | 80.7 | – | – | (634) | 88 |
| 58 | 653 | 80.1 | – | – | 615 | 87 |
| 57 | 633 | 79.6 | – | – | 595 | 85 |
| 56 | 613 | 79.0 | – | – | 577 | 83 |
| 55 | 595 | 78.5 | – | – | 560 | 74 |
| 54 | 577 | 78.0 | – | – | 543 | 72 |
| 53 | 560 | 77.4 | – | – | 525 | 71 |
| 52 | 544 | 76.8 | – | (500) | 512 | 69 |
| 51 | 528 | 76.3 | – | (487) | 496 | 68 |
| 50 | 513 | 75.9 | – | (475) | 481 | 67 |
| 49 | 498 | 75.2 | – | (464) | 469 | 66 |
| 48 | 484 | 74.7 | – | 451 | 455 | 64 |
| 47 | 471 | 74.1 | – | 442 | 443 | 63 |
| 46 | 458 | 73.6 | – | 432 | 432 | 62 |
| 45 | 446 | 73.1 | – | 421 | 421 | 60 |
| 44 | 434 | 72.5 | – | 409 | 409 | 58 |
| 43 | 423 | 72.0 | – | 400 | 400 | 57 |
| 42 | 412 | 71.5 | – | 390 | 390 | 56 |
| 41 | 402 | 70.9 | – | 381 | 381 | 55 |
| 40 | 392 | 70.4 | – | 371 | 371 | 54 |
| 39 | 382 | 69.9 | – | 362 | 362 | 52 |
| 38 | 372 | 69.4 | – | 353 | 353 | 51 |
| 37 | 363 | 68.9 | – | 344 | 344 | 50 |
| 36 | 354 | 68.4 | (109.0) | 336 | 336 | 49 |
| 35 | 345 | 67.9 | (108.5) | 327 | 327 | 48 |
| 34 | 336 | 67.4 | (108.0) | 319 | 319 | 47 |
| 33 | 327 | 66.8 | (107.5) | 311 | 311 | 46 |
| 32 | 318 | 66.3 | (107.0) | 301 | 301 | 44 |
| 31 | 310 | 65.8 | (106.0) | 294 | 294 | 43 |
| 30 | 302 | 65.3 | (105.5) | 286 | 286 | 42 |
| 29 | 294 | 64.7 | (104.5) | 279 | 279 | 41 |
| 28 | 286 | 64.3 | (104.0) | 271 | 271 | 41 |
| 27 | 279 | 63.8 | (103.0) | 264 | 264 | 40 |
| 26 | 272 | 63.3 | (102.5) | 258 | 258 | 38 |
| 25 | 266 | 62.8 | (101.5) | 253 | 253 | 38 |
| 24 | 260 | 62.4 | (101.0) | 247 | 247 | 37 |
| 23 | 254 | 62.0 | 100.0 | 243 | 243 | 36 |
| 22 | 248 | 61.5 | 99.0 | 237 | 237 | 35 |
| 21 | 243 | 61.0 | 98.5 | 231 | 231 | 35 |
| 20 | 238 | 60.5 | 97.8 | 226 | 226 | 34 |
| (18) | 230 | – | 96.7 | 219 | 219 | 33 |
| (16) | 222 | – | 95.5 | 212 | 212 | 32 |
| (14) | 213 | – | 93.9 | 203 | 203 | 31 |
| (12) | 204 | – | 92.3 | 194 | 194 | 29 |
| (10) | 196 | – | 90.7 | 187 | 187 | 28 |
| (8) | 188 | – | 89.5 | 179 | 179 | 27 |
| (6) | 180 | – | 87.1 | 171 | 171 | 26 |
| (4) | 173 | – | 85.5 | 165 | 165 | 25 |
| (2) | 166 | – | 83.5 | 158 | 158 | 24 |
| (0) | 160 | – | 81.7 | 152 | 152 | 24 |
| Numbers with ( ) are for reference. | ||||||