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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

ScaleIndenterMajor Load
F1
N
    E    Applications
A120oDiamond cone490.5100Sheet steel ; shallow case hardened
B1/16" steel ball882.9130Copper, Aluminium alloys, Low Carbon Steel
C120oDiamond cone1373.4100Most Widely Used -Hardened Steels, Cast irons etc
D120oDiamond cone882.9100Thin but hard steels, Ductile Iron (Pearlitic
E1/8" steel ball882.9130Cast Iron, Aluminium, Bearings alloys
F1/16" steel ball490.5130Annealed copper alloys , Soft thin metals
G1/16" steel ball1373.4130Phosphor bronze, beryllium copper, malleable irons, Lead etc
H1/8" steel ball490.5130Soft Metals Plastics etc
K1/8" steel ball1373.4130Soft bearing metals, Plastics, soft materials.
L1/4" steel ball490.5130Soft bearing metals, Plastics, soft materials.
M1/4" steel ball882.9130Soft bearing metals, Plastics, soft materials.
P1/4" steel ball1373.4130Soft bearing metals, Plastics, soft materials.
R1/2" steel ball490.5130Soft bearing metals, Plastics, soft materials.
S1/2" steel ball882.9130Soft bearing metals, Plastics, soft materials.
V1/2" steel ball1373.4130Soft 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



ScaleIndenterMajor Load
( N )
   E   Application
15N120o Diamond cone117.72100Similar to C scale, but for thin materials
30N120o Diamond cone264.87100Same as 15N
45N120o Diamond cone412100Same as 15N
15T1/16" steel ball117.72100Similar to B scale, but for thin materials
30T1/16" steel ball264.87100Same as 15T
45T1/16" steel ball412100Same as 15T
15W1/8" steel ball117.72100For very soft materials
30W1/8" steel ball264.87100For very soft materials
45W1/8" steel ball412100For very soft materials
15X1/4" steel ball117.72100For very soft materials
30X1/4" steel ball264.87100For very soft materials
45X1/4" steel ball412100For very soft materials
15Y1/2" steel ball117.72100For very soft materials
30Y1/2" steel ball264.87100For very soft materials
45Y1/2" steel ball412100For 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  
Corundum9
Topaz8
Quartz7
Orthoclase (Feldspar)6
Aptite5
Fluorite4
Calcite3
Gypsum2
Talc1





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

VPNROCKWELL SCALESROCKWELL Superficial BRINELLSCLERO-
SCOPE
U.T.S.
DPH
HV/10
AB CD G15N30N45NBHN
500kg
BHN
3000kg
 MPa
186592 8087 979287    
178792 7986 969287    
171091 7885 969186    
163391 7784 969185    
155690 7683 969084    
147890 7583 958983    
140089 7482 958982    
132389 7381 958881    
124588 7280 958780    
116087 7180 948779    
107687 7079 948678  101 
100486 6978 948577  99 
94086 6877 938475  97 
90085 6776 938474  95 
86585 6675 938373  92 
83284 6575 928272 73991 
80084 6474 928171 72288 
77283 6373 918070 70587 
74683 6272 917969 68885 
72082 6172 917968 67083 
69781 6071 907867 654812206
67481 5970 907766 634802137
65380 5869 897664 615782069
63380 5769 897563 595762000
61379 5668 887462 577751944
595791205567 887361 560741889
577781205466 877260 543721834
560781195365 877159 523711772
544771195265 867057 512691689
528771185164 866956 496681648
513761175063 866955 481671607
498751174962 856854 469661565
484751164861 856753 455641524
471741164761 846651 443631496
458741154660 846550 432621462
446731154559 836449 421601420
434731144459 836348 409581379
423721134358 826247 400571351
412721134257 826146 390561317
402711124156 816044 381551289
392711124055 806043 371541255
382701113955 805942 362521220
372701103854 795841 353511193
363691103753 795740 344501165
354691093652 785638 336491138
345681093552 785537 327481103
336681083451 775436 319471076
327671083350 775335 311461048
318671073249 765234 301441014
31066106314891765133 29443993
30266105304891755031 28642965
29465104294789755030 27941945
28665104284688744929 27141917
27964103274587734828 26440889
27264103264586734727 25839869
26663102254485724626 25338855
26063101244384724524 24737834
2546210023428371442320124036814
248629922428171432219523435793
243619821417970422118922835772
238619720407869422018422234752
VPNROCKWELL SCALESROCKWELL Superficial BRINELLSCLERO-
SCOPE
U.T.S.
DPH
HV/10
AB CD G15N30N45NBHN
500kg
BHN
3000kg
 MPa






Softer Scales

VPNROCKWELL SCALESROCKWELL Superficial BRINELLSCLERO-
SCOPE
U.T.S.
DPH
HV/10
ABCEFGHK15T30T45TBHN
500kg
BHN
3000kg
 MPa
234609719  77  92806918121834738
230599618  76  92806817921433731
226599617  75  92806817721033717
222589516  74  92796717520832703
217589515  73  92796717120531690
213589414  73  91796616920331683
208579313  71  91786616720030676
204579212  70 10091786516319530662
200569211  69 10091776416219329655
196569110  68 10090776416019028641
19256909  66 9990766315718527627
18855898  64 9890766215418026607
18454887  63 9790756115117626593
18054876  61 9789756014817226579
17653865  59 9689745914516925572
17253854  58 9589745814216525558
16852843  56 9488735714016225545
16451832  54 9388725613715924538
16051821  53 9288725513515624524
15650810  51 9187715413315324517
1525080   49 91877053130150 503
1484979   48 90877052128147  
1444978   46 89866951126144  
1414877   44 88866850124141  
1394776   43 87866849122139  
1374775  10041 86856749120137  
1354674  9939 85856648118135  
1324673  9938 85856647116132  
1304572  9836 84846546114130  
1274571 1009835 83846445112127  
1254470 1009733 82846444110125  
1234469 999631 81836343109123  
1204368 989630 80836242107121  
1184367 989528 79836241106119  
1164266 979527 78826140104117  
1154265 969425 78826039102116  
1144264 969424 77826038101114  
1134163 959322 7681593799112  
1124162 959221 7581583698110  
1114061 949219 7481573596108  
1104060 939118 7381573495107  
1083959 939116 7280563294106  
1073958 929015 7180553192104  
1063857 919013 7180553091102  
1053856 918912 7079542990101  
1043855 908810 697953288999  
1033754 90889 6879532787   
1023753 89877 6778522686   
1013652 88876 6678512585   
1003651 88864 6578512484   
1003550 87863 6577502383   
993549 8785  6477492282   
983548 8685  6377492181   
973447 8584  6276482080   
963446 8583  6176471979   
953345 8483  6076461879   
953344 8482  5975461778   
943243 8382  5875451677   
933242 8281  5875441576   
923141 8281  5774441475   
913140 8180  5674431374   
903139 8079  5574421174   
903038 8079  5473421073   
893037 7978  537341972   
882936 7978 100527340871   
882935 7877 100527240771   
872834 7777 99517239670   
872833 7776 99507238569   
862832 7675 99497138468   
862731 7675 98487137368   
852730 7574 98477136267   
852629 7474 98467036166   
842628 7473 97457035 66   
842527 7373 97457034 65   
832526 7372 97446933 65   
832425 7271 96426933 64   
822424 7171 96426932 64   
822423 7170 96416831 63   
812322 7070 95406831 63   
812321 7069 95396830 62   
802220 6969 95386829 62   
802219 6868 94386729 61   
792118 6867 94376728 61   
792117 6767 93366727 60   
782116 6766 93356626 60   
782015 6666 93346626 59   
77 14 6565 92336625 59   
77 13 6565 92326524 58   
76 12 6464 92326524 58   
76 11 6464 91316523 57   
75 10 6363 91306422 57   
75 9 6262 91296422 56   
74 8 6262 90286421 56   
74 7 6161 90276320 56   
73 6 6161 90266320 55   
73 5 6060 89266319 55   
72 4 5960 89256218 55   
72 3 5959 88246217 54   
71 2 5858 88236217 54   
71 1 5858 88226116 53   
70 0 5757 87216115 53   
VPNROCKWELL SCALESROCKWELL Superficial BRINELLSCLERO-
SCOPE
U.T.S.
DPH
HV/10
ABCEFGHK15T30T45TBHN
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 - 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 11/01/2013