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Rockwell Hardness Conversions

The Rockwell hardness scale is based on a material’s ability to resist permanent deformation. The Rockwell hardness Digital Rockwell Hardness Testertest 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

116 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
 C Scale (1471N)

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.

 

Rockwell
 C Scale (1471N)
Vickers Rockwell Brinell Shore
A Scale (588.4N) B Scale (980.7N) Standard ball Tungsten Carbide Ball
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