Hardness Conversion Chart

Trojan Special Fasteners Ltd can provide material certificates on request for goods; all will have chemical composition data and some will come with mechanical data. Please note material certificates must be requested at the quotation stage.

What is hardness?
Strength and hardness are not the same and one should be careful when determining what kind of fastener you need.

Hardness is defined as a measure of a material's resistance to localised plastic deformation. Plastic deformation is an engineer's way of saying that the deformation is permanent and the material won't return to its original shape, for example, an indentation or scratch on the surface won't 'heal'. In plain English this means the harder a material is, the more difficult it is to scratch, mark or penetrate.

For example, butter is more easily cut/deformed/penetrated by a steel knife than a piece of tungsten. The tungsten won't even be marked by the butter knife because tungsten is very hard. This is also a reason why tungsten is often added as an alloying element in tool steels because it helps to reduce wear at high temperatures and difficult cutting conditions.

What is Indentation Hardness?

Indentation hardness testing refers to the resistance to plastic deformation when metal is subject to a continuous load.

Metals commonly used to make nuts are usually tested using Indentation Hardness tests such as Brinell, Vickers or Rockwell.

It has been shown that there is an approximately linear correlation between indentation hardness and yield strength as well as, more importantly, tensile strength for ferrous (nonaustenitic) hypoeuctoid (less than 0.8% carbon) steels. This means that it is relatively cost-effective and easy to perform non-destructive Rockwell testing of metals.

When choosing a nut it is a good idea to know what your ultimate application is, as this will determine the hardness or tensile strength of the nut.

Table of Hardness Figures

Please note that this table provides approximate equivalents only and should not be relied upon for accuracy. This is because data on it cannot be generated mathematically for a diverse range of materials with different chemical compositions.

Rockwell Rockwell Superficial Brinell Vickers Shore Approx Tensile
A B C D E F 15-N 30-N 45-N 30-T 3000
Kg		 500
Kg		 136
60kg
Brale		 100kg
1/16"
Ball		 150kg
Brale		 100kg
Brale		 100kg
1/8"
Ball		 60kg
1/16"
Ball		 15kg
Brale		 30kg
Brale		 45kg
Brale		 30Kg
1/16"
Ball		 10mm
Steel
Ball		 Diamond
Pyramid		 Sclero-
scope		 psi N/mm2 Kg
f/mm2
86.5   70 78.5     94 86 77.6       1076 101      
86   69 77.7     93.5 85 76.5       1044 99      
85.6   68 76.9     93.2 84.4 75.4       940 97      
85   67 76.1     92.9 83.6 74.2       900 95      
84.5   66 75.4     92.5 82.8 73.2       865 92      
83.9   65 74.5     92.2 81.9 72   739   832 91      
83.4   64 73.8     91.8 81.1 71   722   800 88      
82.8   63 73     91.4 80.1 69.9   705   772 87      
82.3   62 72.2     91.1 79.3 68.8   688   746 85      
81.8   61 71.5     90.7 78.4 67.7   670   720 83      
81.2   60 70.7     90.2 77.5 66.6   654   697 81 320,000 2206 225
80.7   59 69.9     89.8 76.6 65.5   634   674 80 310,000 2137 218
80.1   58 69.2     89.3 75.7 64.3   615   653 78 300,000 2068 211
79.6   57 68.5     88.9 74.8 63.2   595   633 76 290,000 1999 204
79   56 67.7     88.3 73.9 62   577   613 75 282,000 1944 198
78.5 120 55 66.9     87.9 73 60.9   560   595 74 274,000 1889 193
78 120 54 66.1     87.4 72 59.8   543   577 72 266,000 1834 187
77.4 119 53 65.4     86.9 71.2 58.6   525   560 71 257,000 1772 181
76.8 119 52 64.6     86.4 70.2 57.4   500   544 69 245,000 1689 172
76.3 118 51 63.8     85.9 69.4 56.1   487   528 68 239,000 1648 168
75.9 117 50 63.1     85.5 68.5 55   475   513 67 233,000 1606 164
75.2 117 49 62.1     85 67.6 53.8   464   498 66 227,000 1565 160
74.7 116 48 61.4     84.5 66.7 52.5   451   484 64 221,000 1524 155
74.1 116 47 60.8     83.9 65.8 51.4   442   471 63 217,000 1496 153
73.6 115 46 60     83.5 64.8 50.3   432   458 62 212,000 1462 149
73.1 115 45 59.2     83 64 49   421   446 60 206,000 1420 145
72.5 114 44 58.5     82.5 63.1 47.8   409   434 58 200,000 1379 141
72 113 43 57.7     82 62.2 46.7   400   423 57 196,000 1351 138
71.5 113 42 56.9     81.5 61.3 45.5   390   412 56 191,000 1317 134
70.9 112 41 56.2     80.9 60.4 44.3   381   402 55 187,000 1289 131
70.4 112 40 55.4     80.4 59.5 43.1   371   392 54 182,000 1255 128
69.9 111 39 54.6     79.9 58.6 41.9   362   382 52 177,000 1220 124
69.4 110 38 53.8     79.4 57.7 40.8   353   372 51 173,000 1193 122
68.9 110 37 53.1     78.8 56.8 39.6   344   363 50 169,000 1165 119
68.4 109 36 52.3     78.3 55.9 38.4   336   354 49 165,000 1138 116
67.9 109 35 51.5     77.7 55 37.2   327   345 48 160,000 1103 112
67.4 108 34 50.8     77.2 54.2 36.1   319   336 47 156,000 1076 110
66.8 108 33 50     76.6 53.3 34.9   311   327 46 152,000 1048 107
66.3 107 32 49.2     76.1 52.1 33.7   301   318 44 147,000 1014 103
65.8 106 31 48.4     75.6 51.3 32.5   294   310 43 144,000 993 101
65.3 105 30 47.7     75 50.4 31.3   286   302 42 140,000 965 98
64.7 104 29 47     74.5 49.5 30.1   279   294 41 137,000 945 96
64.3 104 28 46.1     73.9 48.6 28.9   271   286 41 133,000 917 94
63.8 103 27 45.2     73.3 47.7 27.8   264   279 40 129,000 889 91
63.3 103 26 44.6     72.8 46.8 26.7   258   272 39 126,000 869 89
62.8 102 25 43.8     72.2 45.9 25.5   253   266 38 124,000 855 87
62.4 101 24 43.1     71.6 45 24.3   247   260 37 121,000 834 85
62 100 23 42.1     71 44 23.1 82 240 201 254 36 118,000 814 83
61.5 99 22 41.6     70.5 43.2 22 81.5 234 195 248 35 115,000 793 81
61 98 21 40.9     69.9 42.3 20.7 81 228 189 243 35 112,000 772 79
60.5 97 20 40.1     69.4 41.5 19.6 80.5 222 184 238 34 109,000 752 77
59 96 18             80 216 179 230 33 106,000 731 75
58 95 16             79 210 175 222 32 103,000 710 72
57.5 94 15             78.5 205 171 213 31 100,000 689 70
57 93 13             78 200 167 208 30 98,000 676 69
56.5 92 12             77.5 195 163 204 29 96,000 662 67
56 91 10             77 190 160 196 28 93,000 641 65
55.5 90 9             76 185 157 192 27 91,000 627 64
55 89 8             75.5 180 154 188 26 88,000 607 62
54 88 7             75 176 151 184 26 86,000 593 60
53.5 87 6             74.5 172 148 180 26 84,000 579 59
53 86 5             74 169 145 176 25 83,000 572 58
52.5 85 4             73.5 165 142 173 25 81,000 558 57
52 84 3             73 162 140 170 25 79,000 545 56
51 83 2             72 159 137 166 24 78,000 538 55
50.5 82 1             71.5 156 135 163 24 76,000 524 53
50 81 0             71 153 133 160 24 75,000 517 53
49.5 80               70 150 130     73,000 503 51
49 79               69.5 147 128          
48.5 78               69 144 126          
48 77               68 141 124          
47 76               67.5 139 122          
46.5 75       99.5       67 137 120          
46 74       99       66 135 118          
45.5 73       98.5       65.5 132 116          
45 72       98       65 130 114          
44.5 71     100 97.5       64.2 127 112          
44 70     99.5 97       63.5 125 110          
43.5 69     99 96       62.8 123 109          
43 68     98 95.5       62 121 107          
42.5 67     97.5 95       61.4 119 106          
42 66     97 94.5       60.5 117 104          
41.8 65     96 94       60.1 116 102          
41.5 64     95.5 93.5       59.5 114 101          
41 63     95 93       58.7 112 99          
40.5 62     94.5 92       58 110 98          
40 61     93.5 91.5       57.3 108 96          
39.5 60     93 91       56.5 107 95          
39 59     92.5 90.5       55.9 106 94          
38.5 58     92 90       55 104 92          
38 57     91 89.5       54.6 102 91          
37.8 56     90.5 89       54 101 90          
37.5 55     90 88       53.2 99 89          
37 54     89.5 87.5       52.5   87          
36.5 53     89 87       51.8   86          
36 52     88 86.5       51   85          
35.5 51     87.5 86       50.4   84          
35 50     87 85.5       49.5   83          
34.8 49     86.5 85       49.1   82          
34.5 48     85.5 84.5       48.5   81          
34 47     85 84       47.7   80          
33.5 46     84.5 83       47   79          
33 45     84 82.5       46.2   79          
32.5 44     83.5 82       45.5   78          
32 43     82.5 81.5       44.8   77          
31.5 42     82 81       44   76          
31 41     81.5 80.5       43.4   75          
30.8 40     81 79.5       43   74          
30.5 39     80 79       42.1   74          
30 38     79.5 78.5       41.5   73          
29.5 37     79 78       40.7   72          
29 36     78.5 77.5       40   71          
28.5 35     78 77       39.3   71          
28 34     77 76.5       38.5   70          
27.8 33     76.5 75.5       37.9   69          
27.5 32     76 75       37.5   68          
27 31     75.5 74.5       36.6   68          
26.5 30     75 74       36   67          
26 29     74 73.5       35.2   66          
25.5 28     73.5 73       34.5   66          
25 27     73 72.5       33.8   65          
24.5 26     72.5 72       33.1   65          
24.2 25     72 71       32.4   64          
24 24     71 70.5       32   64          
23.5 23     70.5 70       31.1   63          
23 22     70 69.5       30.4   63          
22.5 21     69.5 69       29.7   62          
22 20     68.5 68.5       29   62          
21.5 19     68 68       28.1   61          
21.2 18     67.5 67       27.4   61          
21 17     67 66.5       26.7   60          
20.5 16     66.5 66       26   60          
20 15     65.5 65.5       25.3   59          
  14     65 65       24.6   59          
  13     64.5 64.5       23.9   58          
  12     64 64       23.5   58          
  11     63.5 63.5       22.6   57          
  10     62.5 63       21.9   57          
  9     62 62       21.2   56          
  8     61.5 61.5       20.5   56          
  7     61 61       19.8   56          
  6     60.5 60.5       19.1   55          
  5     60 60       18.4   55          
  4     59 59.5       18   55          
  3     58.5 59       17.1   54          
  2     58 58       16.4   54          
  1     57.5 57.5       15.7   53          
  0     57 57       15   53