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Hardness Measurement


Brinell ...... Vickers ...... Rockwell ...... Superficial Rockwell...... Scleroscope......

Knoop...... Jominy...... Moh...... Shore (Durometer)

Equivalent Hardness Table (harder scales)...... Equivalent Hardness Table (softerr scales)

Hardness Comparison chart...... Typical component Surface Hardness......



Methods of Measuring Hardness

Brinell Hardness Test

In this test a hardened steel ball is pressed into the surface of the test material using a prescribed ball. The ball and load have to be selected to suit the material being tested.

The Brinell hardness test consists of indenting the test material with a 10 mm diameter hardened steel or carbide ball subjected to a load of 3000 kgf (29 430 N).   For softer materials the load can be reduced to 1500 kgf (14 715 N) or 500 kgf (4 905 N ) to avoid excessive indentation.   The full load is normally applied for 10 to 15 seconds for harder ferrous metals and for 30 seconds or more for other metals softer metals.  The diameter of the indentation left in the test material is measured with a microscope.

The Brinell hardness number is calculated by dividing the load applied by the surface area of the indentation.

D = Diameter of Ball
D1 = Diameter of indentation
F = applied force



Vickers Hardness Test

In this test a Diamond Indenter is pressed into the surface of the material being tested. Standard loads used include 5, 10, 20, 30,  50, and 100 kgf. (49,05, 98,1 196,2 490,5 and 981 N).
The load is stated in specifying the hardness number i.e HD(10) = 100. the indenter is a square based pyramid (136o included angle )to suit the material being tested


The Hardness Number HD = 1.844 x Load/ Average diagonal length of indentation



Rockwell Hardness Test

In this test a Hard Steel Ball or a Diamond Cone Indenter is pressed into the surface of the material being tested/   The result of the test is read directly from machine.

The indenter is forced into the test material under a preliminary minor load (98N)and after equilibrium are achieved an indicating device, which follows the movements of the indenter, is set to the datum position.   An additional major load is then applied with resulting increase in penetration.   The conditions are then allowed to stabilise and then the additional major load is removed,leaving the minor load in place. The resulting permanent penetration esulting from the application and removal of the additional major load is used to calculate the Rockwell hardness number.

HR = E - e


F1 = additional major
e = permanent increase in depth of penetration due to major load , measured in units of 0.001 mm
E = a constant of 100 units for diamond and ball indenters
HR = Rockwell hardness number
D = diameter of steel ball

Scale Indenter Major Load
F1
N		     E     Applications
A 120oDiamond cone 490.5 100 Sheet steel ; shallow case hardened
B 1/16" steel ball 882.9 130 Copper, Aluminium alloys, Low Carbon Steel
C 120oDiamond cone 1373.4 100 Most Widely Used -Hardened Steels, Cast irons etc
D 120oDiamond cone 882.9 100 Thin but hard steels, Ductile Iron (Pearlitic
E 1/8" steel ball 882.9 130 Cast Iron, Aluminium, Bearings alloys
F 1/16" steel ball 490.5 130 Annealed copper alloys , Soft thin metals
G 1/16" steel ball 1373.4 130 Phosphor bronze, beryllium copper, malleable irons, Lead etc
H 1/8" steel ball 490.5 130 Soft Metals Plastics etc
K 1/8" steel ball 1373.4 130 Soft bearing metals, Plastics, soft materials.
L 1/4" steel ball 490.5 130 Soft bearing metals, Plastics, soft materials.
M 1/4" steel ball 882.9 130 Soft bearing metals, Plastics, soft materials.
P 1/4" steel ball 1373.4 130 Soft bearing metals, Plastics, soft materials.
R 1/2" steel ball 490.5 130 Soft bearing metals, Plastics, soft materials.
S 1/2" steel ball 882.9 130 Soft bearing metals, Plastics, soft materials.
V 1/2" steel ball 1373.4 130 Soft bearing metals, Plastics, soft materials.




Superficial Rockwell Hardness Test

A more surface sensitive measurement of hardness than for the regular Rockwell scales.   This technique is useful for samples with hardness gradients at the surface, to test small areas, and for thin samples.   Superficial Rockwell hardness scales are N and T for metals and W, X, and Y for non-metallic materials and coatings. The Superficial Rockwell hardness test method consists of indenting the test material with a diamond cone (N scale) or hardened steel ball indenter.    The indenter is forced into the test material under a preliminary minor (29.43N) and the conditions are allowed to settle.   Then the indicating device that follows the movements of the indenter is set to a datum position.   An additional major load, is applied with resulting increase in penetration .   The conditions are allowed to settle again and then the additional major load is removed.   The permanent increase in depth of penetration, resulting from the application and removal of the additional major load is used to calculate the Rockwell Superficial hardness number.

HR = E - e


e = permanent increase in depth of penetration due to major load F1, measured in units of 0.001 mm
E = a constant of 100 units for diamond and ball indenters
HR = Rockwell hardness number
D = diameter of steel ball



Scale Indenter Major Load
( N )		    E    Application
15N 120o Diamond cone 117.72 100 Similar to C scale, but for thin materials
30N 120o Diamond cone 264.87 100 Same as 15N
45N 120o Diamond cone 412 100 Same as 15N
15T 1/16" steel ball 117.72 100 Similar to B scale, but for thin materials
30T 1/16" steel ball 264.87 100 Same as 15T
45T 1/16" steel ball 412 100 Same as 15T
15W 1/8" steel ball 117.72 100 For very soft materials
30W 1/8" steel ball 264.87 100 For very soft materials
45W 1/8" steel ball 412 100 For very soft materials
15X 1/4" steel ball 117.72 100 For very soft materials
30X 1/4" steel ball 264.87 100 For very soft materials
45X 1/4" steel ball 412 100 For very soft materials
15Y 1/2" steel ball 117.72 100 For very soft materials
30Y 1/2" steel ball 264.87 100 For very soft materials
45Y 1/2" steel ball 412 100 For very soft materials




The Shore (Scleroscope ) Hardness Test

The Scleroscope test consists of dropping a diamond tipped hammer, which falls inside a glass tube under the force of its own weight from a fixed height, onto the test specimen.   The height of the rebound travel of the hammer is measured on a graduated scale.  The harder the material, the higher the rebound.   The scale of the rebound is arbitrarily chosen and consists on Shore units, divided into 100 parts, which represent the average rebound from pure hardened high-carbon steel.   The scale is continued higher than 100 to to allow for metals having greater hardness.

The shore scleroscope test does not normally mark the material under test.   The Shore Scleroscope measures hardness in relation to the elasticity of the material.  

Advantages of this method are portability and non-marking of the test surface.



Knoop

The Knoop indenter has a polished rhombohedral shape with an included longitudinal angle of 172° 30’ and an included transverse angle of 130° 0’.   The narrowness of the indenter makes it ideal for testing specimens with steep hardness gradients and coatings.  Knoop is a better choice for hardness testing of hard brittle materials.



Jominy Hardenability

The Jominy test involves heating a test specimen of steel 25mm diameter and 100mm long to an austenitising temperature and quenching from one end with a controlled and standardized jet of water.   After quenching, the hardness is measured at intervals taken form the quenched end.   The hardness gradient along the test surface provides an indication of the material’s hardenability.




Moh's Hardness Scale

The Moh's hardness scale consists of 10 minerals arranged in order from 1 to 10.    Diamond is rated as the hardest and is indexed as 10; talc as the softest with index number 1.   Each mineral in the scale will scratch all those below it as follows:


Diamond  10  
Corundum 9
Topaz 8
Quartz 7
Orthoclase (Feldspar) 6
Aptite 5
Fluorite 4
Calcite 3
Gypsum 2
Talc 1




Shore (Durometer) test

The hardness testing of plastics is most commonly measured by the Shore (Durometer) test.  This test measures the resistance of the plastic toward indentation.   The scale provide an empirical hardness value that doesn't relate directly to the mechanical properties of the material being tested.   Shore Hardness, using either the Shore A or Shore D scale, is the preferred method for rubbers/elastomers and is also commonly used for 'softer' plastics such as polyolefins, fluoropolymers, and vinyls.   The Shore A scale is used for 'softer' rubbers while the Shore D scale is used for 'harder' rubbers.

The Shore hardness is measured with an apparatus known as a Durometer and consequently is also known as 'Durometer hardness'.   The hardness value is determined by the penetration of the Durometer indenter foot into the sample.   If the indenter completely penetrates the sample, a reading of 0 is obtained, and if no penetration occurs, a reading of 100 results.    Because of the resilience of rubbers and plastics, the hardness reading my change over time - so the indentation time is sometimes reported along with the hardness number.   The test method is identified in standard ISO 868.

The results obtained from this test are a useful measure of relative resistance to indentation of various grades of polymers.   However, the Shore Durometer hardness test does not serve well as a predictor of other properties such as strength or resistance to scratches, abrasion, or wear, and should not be used alone for product design specifications.


Tables showing the comparative hardness numbers between scales is provided at site the following sites.....

  1. Gordon England.....
  2. Corrosion Products Handbook
Equivalent Hardness Conversion Tables



Harder Scales

VPN ROCKWELL SCALES ROCKWELL Superficial BRINELL SCLERO-
SCOPE		 U.T.S.
DPH
HV/10		 A B C D G 15N 30N 45N BHN
500kg		 BHN
3000kg		   MPa
1865 92   80 87   97 92 87        
1787 92   79 86   96 92 87        
1710 91   78 85   96 91 86        
1633 91   77 84   96 91 85        
1556 90   76 83   96 90 84        
1478 90   75 83   95 89 83        
1400 89   74 82   95 89 82        
1323 89   73 81   95 88 81        
1245 88   72 80   95 87 80        
1160 87   71 80   94 87 79        
1076 87   70 79   94 86 78     101  
1004 86   69 78   94 85 77     99  
940 86   68 77   93 84 75     97  
900 85   67 76   93 84 74     95  
865 85   66 75   93 83 73     92  
832 84   65 75   92 82 72   739 91  
800 84   64 74   92 81 71   722 88  
772 83   63 73   91 80 70   705 87  
746 83   62 72   91 79 69   688 85  
720 82   61 72   91 79 68   670 83  
697 81   60 71   90 78 67   654 81 2206
674 81   59 70   90 77 66   634 80 2137
653 80   58 69   89 76 64   615 78 2069
633 80   57 69   89 75 63   595 76 2000
613 79   56 68   88 74 62   577 75 1944
595 79 120 55 67   88 73 61   560 74 1889
577 78 120 54 66   87 72 60   543 72 1834
560 78 119 53 65   87 71 59   523 71 1772
544 77 119 52 65   86 70 57   512 69 1689
528 77 118 51 64   86 69 56   496 68 1648
513 76 117 50 63   86 69 55   481 67 1607
498 75 117 49 62   85 68 54   469 66 1565
484 75 116 48 61   85 67 53   455 64 1524
471 74 116 47 61   84 66 51   443 63 1496
458 74 115 46 60   84 65 50   432 62 1462
446 73 115 45 59   83 64 49   421 60 1420
434 73 114 44 59   83 63 48   409 58 1379
423 72 113 43 58   82 62 47   400 57 1351
412 72 113 42 57   82 61 46   390 56 1317
402 71 112 41 56   81 60 44   381 55 1289
392 71 112 40 55   80 60 43   371 54 1255
382 70 111 39 55   80 59 42   362 52 1220
372 70 110 38 54   79 58 41   353 51 1193
363 69 110 37 53   79 57 40   344 50 1165
354 69 109 36 52   78 56 38   336 49 1138
345 68 109 35 52   78 55 37   327 48 1103
336 68 108 34 51   77 54 36   319 47 1076
327 67 108 33 50   77 53 35   311 46 1048
318 67 107 32 49   76 52 34   301 44 1014
310 66 106 31 48 91 76 51 33   294 43 993
302 66 105 30 48 91 75 50 31   286 42 965
294 65 104 29 47 89 75 50 30   279 41 945
286 65 104 28 46 88 74 49 29   271 41 917
279 64 103 27 45 87 73 48 28   264 40 889
272 64 103 26 45 86 73 47 27   258 39 869
266 63 102 25 44 85 72 46 26   253 38 855
260 63 101 24 43 84 72 45 24   247 37 834
254 62 100 23 42 83 71 44 23 201 240 36 814
248 62 99 22 42 81 71 43 22 195 234 35 793
243 61 98 21 41 79 70 42 21 189 228 35 772
238 61 97 20 40 78 69 42 20 184 222 34 752
VPN ROCKWELL SCALES ROCKWELL Superficial BRINELL SCLERO-
SCOPE		 U.T.S.
DPH
HV/10		 A B C D G 15N 30N 45N BHN
500kg		 BHN
3000kg		   MPa





Softer Scales

VPN ROCKWELL SCALES ROCKWELL Superficial BRINELL SCLERO-
SCOPE		 U.T.S.
DPH
HV/10		 A B C E F G H K 15T 30T 45T BHN
500kg		 BHN
3000kg		   MPa
234 60 97 19     77     92 80 69 181 218 34 738
230 59 96 18     76     92 80 68 179 214 33 731
226 59 96 17     75     92 80 68 177 210 33 717
222 58 95 16     74     92 79 67 175 208 32 703
217 58 95 15     73     92 79 67 171 205 31 690
213 58 94 14     73     91 79 66 169 203 31 683
208 57 93 13     71     91 78 66 167 200 30 676
204 57 92 12     70   100 91 78 65 163 195 30 662
200 56 92 11     69   100 91 77 64 162 193 29 655
196 56 91 10     68   100 90 77 64 160 190 28 641
192 56 90 9     66   99 90 76 63 157 185 27 627
188 55 89 8     64   98 90 76 62 154 180 26 607
184 54 88 7     63   97 90 75 61 151 176 26 593
180 54 87 6     61   97 89 75 60 148 172 26 579
176 53 86 5     59   96 89 74 59 145 169 25 572
172 53 85 4     58   95 89 74 58 142 165 25 558
168 52 84 3     56   94 88 73 57 140 162 25 545
164 51 83 2     54   93 88 72 56 137 159 24 538
160 51 82 1     53   92 88 72 55 135 156 24 524
156 50 81 0     51   91 87 71 54 133 153 24 517
152 50 80       49   91 87 70 53 130 150   503
148 49 79       48   90 87 70 52 128 147    
144 49 78       46   89 86 69 51 126 144    
141 48 77       44   88 86 68 50 124 141    
139 47 76       43   87 86 68 49 122 139    
137 47 75     100 41   86 85 67 49 120 137    
135 46 74     99 39   85 85 66 48 118 135    
132 46 73     99 38   85 85 66 47 116 132    
130 45 72     98 36   84 84 65 46 114 130    
127 45 71   100 98 35   83 84 64 45 112 127    
125 44 70   100 97 33   82 84 64 44 110 125    
123 44 69   99 96 31   81 83 63 43 109 123    
120 43 68   98 96 30   80 83 62 42 107 121    
118 43 67   98 95 28   79 83 62 41 106 119    
116 42 66   97 95 27   78 82 61 40 104 117    
115 42 65   96 94 25   78 82 60 39 102 116    
114 42 64   96 94 24   77 82 60 38 101 114    
113 41 63   95 93 22   76 81 59 37 99 112    
112 41 62   95 92 21   75 81 58 36 98 110    
111 40 61   94 92 19   74 81 57 35 96 108    
110 40 60   93 91 18   73 81 57 34 95 107    
108 39 59   93 91 16   72 80 56 32 94 106    
107 39 58   92 90 15   71 80 55 31 92 104    
106 38 57   91 90 13   71 80 55 30 91 102    
105 38 56   91 89 12   70 79 54 29 90 101    
104 38 55   90 88 10   69 79 53 28 89 99    
103 37 54   90 88 9   68 79 53 27 87      
102 37 53   89 87 7   67 78 52 26 86      
101 36 52   88 87 6   66 78 51 25 85      
100 36 51   88 86 4   65 78 51 24 84      
100 35 50   87 86 3   65 77 50 23 83      
99 35 49   87 85     64 77 49 22 82      
98 35 48   86 85     63 77 49 21 81      
97 34 47   85 84     62 76 48 20 80      
96 34 46   85 83     61 76 47 19 79      
95 33 45   84 83     60 76 46 18 79      
95 33 44   84 82     59 75 46 17 78      
94 32 43   83 82     58 75 45 16 77      
93 32 42   82 81     58 75 44 15 76      
92 31 41   82 81     57 74 44 14 75      
91 31 40   81 80     56 74 43 13 74      
90 31 39   80 79     55 74 42 11 74      
90 30 38   80 79     54 73 42 10 73      
89 30 37   79 78     53 73 41 9 72      
88 29 36   79 78   100 52 73 40 8 71      
88 29 35   78 77   100 52 72 40 7 71      
87 28 34   77 77   99 51 72 39 6 70      
87 28 33   77 76   99 50 72 38 5 69      
86 28 32   76 75   99 49 71 38 4 68      
86 27 31   76 75   98 48 71 37 3 68      
85 27 30   75 74   98 47 71 36 2 67      
85 26 29   74 74   98 46 70 36 1 66      
84 26 28   74 73   97 45 70 35   66      
84 25 27   73 73   97 45 70 34   65      
83 25 26   73 72   97 44 69 33   65      
83 24 25   72 71   96 42 69 33   64      
82 24 24   71 71   96 42 69 32   64      
82 24 23   71 70   96 41 68 31   63      
81 23 22   70 70   95 40 68 31   63      
81 23 21   70 69   95 39 68 30   62      
80 22 20   69 69   95 38 68 29   62      
80 22 19   68 68   94 38 67 29   61      
79 21 18   68 67   94 37 67 28   61      
79 21 17   67 67   93 36 67 27   60      
78 21 16   67 66   93 35 66 26   60      
78 20 15   66 66   93 34 66 26   59      
77   14   65 65   92 33 66 25   59      
77   13   65 65   92 32 65 24   58      
76   12   64 64   92 32 65 24   58      
76   11   64 64   91 31 65 23   57      
75   10   63 63   91 30 64 22   57      
75   9   62 62   91 29 64 22   56      
74   8   62 62   90 28 64 21   56      
74   7   61 61   90 27 63 20   56      
73   6   61 61   90 26 63 20   55      
73   5   60 60   89 26 63 19   55      
72   4   59 60   89 25 62 18   55      
72   3   59 59   88 24 62 17   54      
71   2   58 58   88 23 62 17   54      
71   1   58 58   88 22 61 16   53      
70   0   57 57   87 21 61 15   53      
VPN ROCKWELL SCALES ROCKWELL Superficial BRINELL SCLERO-
SCOPE		 U.T.S.
DPH
HV/10		 A B C E F G H K 15T 30T 45T BHN
500kg		 BHN
3000kg		   MPa





Figure comparing hardness scales




Table of Components showing relevant surface Hardness values

Important Notes:
Values below are typical of high specification components.. Lower values are likely in more general applications...

Component Hardness Scale
     
Hardened Track for Roller 670-840 HV
Hardened Machine slideway 70-75 HS
Surface Hardened Gear (High spc'n) 58-63 RC
Modern Rails (Used for Normal traffic) 300-340 HV
Modern Rails (High Duty) 340 -420 HV
Shear Blades 81-85 RC
Carbide Dies (Drawing , Forming etc) 80-92 RA
Mild steel components 120 HV
Wrought iron 102 HV
Axe 600 HV
Fork/Rake 700 HV
Kitchen knife 680 HV
Stainless table knife 550 HV
Hammer Face 660 HV
Chisel 600 HV
File 60-61 RC
Drill Bit HSS 63-65 RC
Drill Bit Cobalt 66-67 RC




Links Providing Relevant Information
  1. Gordon England ..Thermal Spraying Specialist with detailed information on Hardness Testing / Corrosion
  2. Hardness Testers..Equipment supplier with detailed information on Hardness Testing / Corrosion
  3. Materials Co UK - Rubber Hardness Testing..Useful Notes and references
  4. NPL - site search (Hardness Testing )..Authoritative source of information on hardness testing (use search to find)
  5. Cambridge U. Jominy Test..Jominy test examples and notes
  6. Material Hardness..A very detailed document covering most hardness testing methods



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Last Updated 19/01/2013