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Hardness Conversion Chart & Calculator

Rockwell Hardness

Brinell Hardness

Vickers Hardness

Definition of Hardness

Hardness is a measure of how well a solid material resists permanent shape change when a compressive force is applied. Hardness is dependant on many factors including strength of intermolecular bonds, ductility, elastic stiffness, plasticity, strain, strength, toughness, and many more.

Hardness Tests: Measuring Hardness

There are three ways hardness is typicall measured:

Scratch Hardness

Scratch Hardness testing is based on the idea that harder materials will scratch softer materials.

Indentation Hardness

Hardness tester for hardness conversion charts

A typical hardness tester…

Indentation hardness measures the resistance of a sample to deformation due to a constant compression load from a sharp object. After the material under test is subjected to a specially loaded and dimensioned indenter, the dimensions of the indentation left behind in the test subject determine the hardness.

This is the most common method of hardness testing used for CNC and machining purposes, and the Rockwell, Vickers, Shore, and Brinell Hardness scales are all based on Indentation Hardness.

Rebound Hardness

In Rebound Hardness measurements, the height of the “bounce” of a dimaond tipped hammer dropped from a fixed height onto the test material determines its hardness.

Rockwell Hardness Test (HR)

In the Rockwell Hardness Test (whose values are referred to with the abbreviation “HR”), a diamond cone or steel ball indenter is used. The indenter is forced into the test material under a minor load, usually 10 kgf. When equilibrium is reached (i.e. no further indentation at that load is happening), a datum position is established. An additional major load is applied, which increases penetration. Removing the major load results in a minor recovery of the material in most cases. The difference between the indentation after that minor recovery and the datum established by the minor load may be used to calculate the Rockwell hardness number.

The various Rockwell Hardness Scales differ in the nature of the indenter as well as the Major Load:

Rockwell Hardness Scales

Testing parameters for the various Rockwell Hardness Scales…

The Rockwell Hardness Test is conveient to automate, but it suffers from many arbitrary scales and possible effects from the specimen support anvil. The Vickers and Brinell methods don’t suffer from this effect.

Brinell Hardness Test (BHN)

The Brinell Hardness Test consists of indenting the test material with a 10mm diameter hardened steel or carbide ball subjected to a load of 3000 kg. For softer materials, there are alternate scales using a 1500 kg or 500 kg load to avoid excessive indentation.

The full load is applied for 10 to 15 seconds for iron or steel and at least 30 seconds for other materials. The diameter of the indentation left is measured by a low powered microscope. The Brinell Hardness Number may be calculated from the diameter of that indentation. The average of two measurements taken at right angles is used for the diameter to ensure accuracy.

Compared to the other test methods, the Brinell ball makes the deepest and widest indentation, so the test results average hardness over a wider area. This can result in more accurate results when there are multiple grain structures and other irregularities in material uniformity.

Vickers Hardness Test (HV)

The Vickers Hardness Test uses a diamond indenter in the form of a right pyramid with a square base and an angle of 136 degress between opposite faces. The indenter is subjected to a load of 1 to 100 kgf. the full load is applied for 10 to 15 seconds. The two diagonals left in the surface of the material are measured using a microscope and their average is taken. From this, the area of the sloping surface of the indentation is calculated, and from that the Vickers Hardness may be determined.

Surprisingly, different loading settings give practically identical hardness numbers on uniform material, which is much better than the arbitrary changing of scale with the other hardness testing methods. The advantages of the Vickers hardness test are that extremely accurate readings can be taken, and just one type of indenter is used for all types of metals and surface treatments. The disadvantage is that the machines that take the reading are large floor-standing units (not benchtop), and they’re more expensive than Brinell or Rockwell machines.

Other Hardness Scales

The Rockwell, Brinell, and Vickers are the most common hardness scales, but there are many others:

– Shore Scleroscope

– Knoop

– Leeb (HLD): Leeb is a rebound hardness test that was developed in 1975 to provide a portable hardness test for metals.

Janka Hardness: Janka is used exclusively for wood, but it can be very helpful when CNC’ing wood.

G-Wizard Hardness Conversion Charts & Calculator

Our G-Wizard Calculator software includes a hardness conversion calculator because it has a full set of hardness conversion charts and a calculator built right in on the “Quick Refs” tab:

Hardness conversion calculator for Rockwell, Brinell, Vickers, Shore Scleroscope, and Tensile Strength…

The Hardness Conversion Calculator is particularly handy.  Enter a from value, select the from units, enter the “to” units, and G-Wizard will give you a value (if there is one) in the new hardness units.  Here’s a closeup of the unit selector:

hardness conversion calculator

Here’s something else–you can get lifetime access to all the reference calculators and materials except the Feeds and Speeds Calculator just by signing up for a 30-Day Free Trial of G-Wizard. That’s right, it is completely free to access all that just by signing up for a free trial and you’ll also get all the upgrades and customer service for life! Plus, buy the $79 version and you get up to 1 HP on the Feeds and Speeds too for life.

So what’s the catch? Why does anyone ever pay more than $79?

Many hobbyists don’t pay more than $79, BTW. The catch is a spindle power limit. When you buy the 1 year G-Wizard for $79, you get 1 year of unlimited spindle power for Feeds and Speeds. When that expires, you get a spindle power limit of 1 HP. That limit is based on however many years you subscribe for. You can increase it any time you like by renewing the subscription. Or, if you don’t like subscriptions, you can also by the product outright. And we never charge for updates or customer service.

So go ahead, give G-Wizard a free 30 day trial. You’ll be surprised at all the time it saves you on things like Tap Drill Sizes, not to mention the longer tool life, better surface finish, and shorter cycle times you’ll get from better Feeds and Speeds.

Hardness Conversion Charts and Tables

hardness conversion chart

Rockwell A Rockwell B Rockwell C Rockwell D Rockwell 15-N Rockwell 30-N Rockwell 45-N Brinell Std Brinell Hultgren Brinell Tungsten Vickers Shore Sclero-Scope Approx Tensile Strength (psi)
85.6   68 76.9 93.2 84.4 75.4       1114 97  
85   67 76.1 92.9 83.6 74.2       1060 95  
84.5   66 75.4 92.5 82.8 73.3       1021 92  
83.9   65 74.5 92.2 81.9 72     739 940 91  
83.4   64 73.8 91.8 81.1 71     722 905 88  
82.8   63 73 91.4 80.1 69.9     705 867 87  
82.3   62 72.2 91.1 79.3 68.8     688 803 85  
81.8   61 71.5 90.7 78.4 67.7     670 775 83  
81.2   60 70.7 90.2 77.5 66.6   613 654 746 81 320000
80.7   59 69.9 89.8 76.6 65.5   599 634 727 80 310000
80.1   58 69.2 89.3 75.7 64.3   587 615 710 78 300000
79.6   57 68.5 88.9 74.8 63.2   575 595 694 76 290000
79   56 67.7 88.3 73.9 62   561 577 649 75 282000
78.5   55 66.9 87.9 73 60.9   546 560 639 74 274000
78   54 66.1 87.4 72 59.8   534 543 606 72 266000
77.4 120 53 65.4 86.9 71.2 58.6   519 525 587 71 257000
76.8 119 52 64.6 86.4 70.2 57.4 500 508 512 565 69 245000
76.3 119 51 63.8 85.9 69.4 56.1 487 494 496 551 68 239000
75.9 118 50 63.1 85.5 68.5 55 475 481 481 542 67 233000
75.2 118 49 62.1 85 67.6 53.8 464 469 469 534 66 227000
74.7 117 48 61.4 84.5 66.7 52.5 451 455 455 502 64 221000
74.1 117 47 60.8 83.9 65.8 51.4 442 443 443 489 63 217000
73.6 116 46 60 83.5 64.8 50.3 432 432 432 474 62 212000
73.1 115 45 59.2 83 64 49 421 421 421 460 60 206000
72.5 115 44 58.5 82.5 63.1 47.8 409 409 409 435 58 200000
72 114 43 57.7 82 62.2 46.7 400 400 400 423 57 196000
71.5 114 42 56.9 81.5 61.3 45.5 390 390 390 401 56 191000
70.9 113 41 56.2 80.9 60.4 44.3 381 381 381 390 55 187000
70.4 112 40 55.4 80.4 59.5 43.1 371 371 371 385 54 182000
69.9 111 39 54.6 79.9 58.6 41.9 362 362 362 380 52 177000
69.4 111 38 53.8 79.4 57.7 40.8 353 353 353 361 51 173000
68.9 110 37 53.1 78.8 56.8 39.6 344 344 344 352 50 169000
68.4 109 36 52.3 78.3 55.9 38.4 336 336 336 335 49 165000
67.9 109 35 51.5 77.7 55 37.2 327 327 327 320 48 160000
67.4 108 34 50.8 77.2 54.2 36.1 319 319 319 312 47 156000
66.8 107 33 50 76.6 53.3 34.9 311 311 311 305 46 152000
66.3 106 32 49.2 76.1 52.1 33.7 301 301 301 291 44 147000
65.8 105 31 48.4 75.6 51.3 32.5 294 294 294 285 43 144000
65.3 105 30 47.7 75 50.4 31.3 286 286 286 278 42 140000
64.7 104 29 47 74.5 49.5 30.1 279 279 279 272 41 137000
64.3 103 28 46.1 73.9 48.6 28.9 271 271 271 261 41 133000
63.8 102 27 45.2 73.3 47.7 27.8 264 264 264 258 40 129000
63.3 101 26 44.6 72.8 46.8 26.7 258 258 258 250 38 126000
62.8 100 25 43.8 72.2 45.9 25.5 253 253 253 246 38 124000
62.4 99 24 43.1 71.6 45 24.3 247 247 247 240 37 121000
62 99 23 42.1 71 44 23.1 243 243 243 235 36 118000
61.5 98 22 41.6 70.5 43.2 22 237 237 237 226 35

115000

 

 
 

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Hardness Conversion Chart, Calculator & Tests for Rockwell, Brinell, Vickers and More
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