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### Hardness Measurement

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

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 LoadF1N 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 degrees 30 degrees and an included transverse angle of 130 degrees 0 degrees.   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 materials 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.

Equivalent Hardness Conversion Tables

Harder Scales

 VPN ROCKWELL SCALES ROCKWELL Superficial BRINELL SCLERO-SCOPE U.T.S. DPHHV/10 A B C D G 15N 30N 45N BHN500kg BHN3000kg 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. DPHHV/10 A B C D G 15N 30N 45N BHN500kg BHN3000kg MPa

Softer Scales

 VPN ROCKWELL SCALES ROCKWELL Superficial BRINELL SCLERO-SCOPE U.T.S. DPHHV/10 A B C E F G H K 15T 30T 45T BHN500kg BHN3000kg 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. DPHHV/10 A B C E F G H K 15T 30T 45T BHN500kg BHN3000kg 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