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Hardness Conversion Numbers

Birnell
3000 kg Load
10 mm Ball		 Rockwell Shore
Sclero-
scope		 Tensile
Strength
psi
(approx.)
Diameter
Millimeters		 Hardness
Number		 A Scale B Scale C Scale 15-N Scale
2.25
2.30
2.35
2.40
2.45		 745
712
682
653
627		 84.1
...
82.2
81.2
80.5		 ...
...
...
...
...		 65.3
...
61.7
60.0
58.7		 92.3
...
91.0
90.2
89.6		 91
...
84
81
79		 ...
...
...
...
...
2.50
2.55
2.60
2.65
2.70		 601
578
555
534
514		 79.8
79.1
78.4
77.8
76.9		 ...
...
...
...
...		 57.3
56.0
54.7
53.5
52.1		 89.0
88.4
87.8
87.2
86.5		 77
75
73
71
70		 ...
...
298000
288000
274000
2.75
2.80
2.85
2.90
2.95		 495
477
461
444
429		 76.3
75.6
74.9
74.2
73.4		 ...
...
...
...
...		 51.0
49.6
48.5
47.1
45.7		 85.9
85.3
84.7
84.0
83.4		 68
66
65
63
61		 264000
252000
242000
230000
219000
3.00
3.05
3.10
3.15
3.20		 415
401
388
375
363		 72.8
72.0
71.4
70.6
70.0		 ...
...
...
...
...		 44.5
43.1
41.8
40.4
39.1		 82.8
82.0
81.4
80.6
80.0		 59
58
56
54
52		 212000
202000
193000
184000
177000
3.25
3.30
3.35
3.40
3.45		 352
341
331
321
311		 69.3
68.7
68.1
67.5
66.9		 110.0
109.0
108.5
108.0
107.5		 37.9
36.6
35.5
34.3
33.1		 79.3
78.6
78.0
77.3
76.7		 51
50
48
47
46		 170000
163000
158000
152000
147000
3.50
3.55
3.60
3.65
3.70		 302
293
285
277
269		 66.3
65.7
65.3
64.6
64.1		 107.0
106.0
105.5
104.5
104.0		 32.1
30.9
29.9
28.8
27.6		 76.1
75.5
75.0
74.4
73.7		 45
43
...
41
40		 143000
139000
136000
131000
128000
3.75
3.80
3.85
3.90
3.95		 262
255
248
241
235		 63.6
63.0
62.5
61.8
61.4		 103.0
102.0
101.0
100.0
99.0		 26.6
25.4
24.2
22.8
21.7		 73.1
72.5
71.7
70.9
70.3		 39
38
37
36
35		 125000
121000
118000
114000
111000
4.00
4.05
4.10
4.15
4.20		 229
223
217
212
207		 60.8
...
...
...
...		 98.2
97.3
96.4
95.5
94.6		 20.5
18.8
17.5
16.0
15.2		 69.7
...
...
...
...		 34
...
33
...
32		 109000
104000
103000
100000
99000
4.25
4.30
4.35
4.40
4.45		 201
197
192
187
183		 ...
...
...
...
...		 93.8
92.8
91.9
90.7
90.0		 13.8
12.7
11.5
10.0
9.0		 ...
...
...
...
...		 31
30
29
...
28		 97000
94000
92000
90000
89000
4.50
4.55
4.60
4.65
4.70		 179
174
170
167
163		 ...
...
...
...
...		 89.0
87.8
86.8
86.0
85.0		 8.0
6.4
5.4
4.4
3.3		 ...
...
...
...
...		 27
...
26
...
25		 88000
86000
84000
83000
82000
4.80
4.90
5.00
5.10
5.20		 156
149
143
137
131		 ...
...
...
...
...		 82.9
80.8
78.7
76.4
74.0		 0.9
...
...
...
...		 ...
...
...
...
...		 ...
23
22
21
...		 80000
...
...
...
...
5.30
5.40
5.50
5.60		 126
121
116
111		 ...
...
...
...		 72.0
69.8
67.6
65.7		 ...
...
...
...		 ...
...
...
...		 20
19
18
15		 ...
...
...
...

Rockwell Birnell
500 kg Load
10 mm Ball
B Scale F Scale 15-T Scale 30-T Scale E Scale H Scale A Scale
74
72
70
68
66		 99.0
98.0
97.0
95.5
94.5		 ...
84.0
83.5
...
82.0		 66.0
65.0
63.5
62.0
60.5		 ...
...
99.5
98.0
97.0		 ...
...
...
...
...		 46.0
45.0
44.0
43.0
42.0		 118
114
110
107
104
64
62
60
58
56		 93.5
92.0
91.0
90.0
89.0		 81.5
...
...
79.5
79.0		 59.5
58.0
56.5
55.0
54.0		 95.5
94.5
93.0
92.0
90.5		 ...
...
...
...
...		 41.5
40.5
39.5
38.5
...		 101
98
95
92
90
54
52
50
48
46		 87.5
86.5
85.5
84.5
83.0		 ...
77.5
77.0
...
75.5		 52.5
51.0
49.5
48.5
47.0		 89.5
88.0
87.0
85.5
84.5		 ...
...
...
...
...		 37.0
36.0
35.0
34.5
33.5		 87
85
83
81
...
44
42
40
38
36		 82.0
81.0
79.5
78.5
77.5		 75.0
...
73.5
73.0
...		 45.5
44.0
43.0
41.5
40.0		 83.5
82.0
81.0
79.5
78.5		 ...
...
...
...
100.0		 32.5
31.5
...
30.0
29.0		 78
76
...
73
...
34
32
30
28
26		 76.5
75.0
74.0
73.0
72.0		 71.5
71.0
70.5
...
69.0		 38.5
37.5
36.0
34.5
33.0		 77.0
76.0
75.0
73.5
72.5		 99.0
98.5
...
97.0
...		 28.0
27.5
26.5
25.5
24.5		 70
...
67
66
65
24
22
20
18
16		 70.5
69.5
68.5
67.0
66.0		 68.5
...
...
66.5
66.0		 32.0
30.5
29.0
27.5
26.0		 71.0
70.0
68.5
67.5
66.5		 95.5
95.0
...
93.5
...		 24.0
23.0
22.0
...
20.5		 ...
...
...
...
...
14
12
10
8		 65.0
64.0
63.0
61.5		 ...
64.5
64.0
63.5		 25.0
23.5
22.0
20.5		 65.0
64.0
62.5
61.5		 92.0
91.5
90.5
90.0		 ...
...
...
...		 ...
...
57
...
6
4
2
0		 60.5
59.5
58.0
57.0		 ...
62.0
61.5
...		 19.5
18.0
16.5
15.0		 60.5
59.0
58.0
57.0		 ...
88.5
...
87.0		 ...
...
...
...		 ...
...
54
53

Rockwell Hardness Scales
Scale Major
Load, kg		 Indenter Use of Scale
A 60 Diamond Cone Extremely hard material such as tungsten carbide or hard sheet material too thin for heavy load.
B 100 1/16" ball Materials of B 0 to B 100 hardness.
C 150 Diamond Cone Materials of C 20 to C 70 hardness
E 100 1/8" ball Very soft materials such as bearing metals.
F 60 1/16" ball Very soft materials such as bearing metals.
H 60 1/8" ball Very soft materials such as bearing metals.
Rockwell Superficial Hardness Scales
15-N 15 Diamond Cone Materials comparable in hardness of C 20 to C70
15-T 15 1/16" ball Materials comparable in hardness of B 0 to B 100
30-T 30 1/16" ball Materials comparable in hardness of B 0 to B 100

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