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

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Hardness Conversion Chart & Calculator

Rockwell Hardness

Brinell Hardness

Vickers Hardness

      Article on Work Hardening / Strain Hardening

Definition of Hardness

Hardness signifies how effectively a solid material can resist permanent deformation when subjected to a compressive force. It’s contingent on a wide range of factors including the robustness of intermolecular bonds, ductility, elastic rigidity, plasticity, strain, strength, toughness, amongst many others.

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

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:

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 tungsten 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:

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 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 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

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