Hardness converter HRC, HB, HV, HRB and more

Rockwell HRC, HRB, HRA and HRD; superficial 15N/30N/45N and 15T/30T/45T; Brinell HB/HBW; Vickers HV; Knoop HK; Shore scleroscope HS; and an estimated tensile strength Rm. Scale-to-scale equivalences follow ASTM E140 for non-austenitic steels, with their own tables for austenitic stainless, nickel, brass and aluminium. Rm comes from ISO 18265 annex A, a different standard: ASTM E140 does not publish Rm.

No. Each test uses a different indenter and load. The conversion is empirical: it is used to compare tokens or certificates, but if the plan requires HRC, it must be measured in HRC (and the same with HB, HV, etc.).

HRC (diamond cone, 150 kgf) for hardened steels ~20–68 HRC. HRB (ball, 100 kgf) for soft and many non-ferrous steels. Below ~20 HRC it is advisable to look at HRB or HB.

Low load Rockwell tests for thin layers, cements or thin pieces where standard HRC would deform too much. The N uses a cone indenter; the T uses ball (softer metals).

No. HS here is the Shore (rebound) scleroscope used on metals. Shore A/D is another test for elastomers and plastics: do not mix them.

It is an estimate, and it is worth knowing where it comes from: ASTM E140 publishes no tensile strength in any of its tables. The Rm correlation is in ISO 18265 annex A, and only for unalloyed or low-alloy steel and cast steel. It does not hold for austenitic stainless, grey iron, as-quenched steel or work-hardened material. We cut it at 1500 MPa, where the correlation stops describing anything real. It does not replace a tensile test.

Yes, by picking the family. The tool carries each one's own table: austenitic stainless (ASTM E140 table 5), nickel (table 3), brass (table 4) and wrought aluminium (table 9). Applying the steel one to everything is the classic mistake and it costs you: in brass it is 8 HRB points, and in austenitic at 100 HRB the steel table falls 28 HB short. Much of that error comes from steel being measured at 3000 kgf while brass and aluminium use 500.

Because that test does not reach that hardness, and saying so is more useful than inventing a number. Above 650 HBW the carbide ball deforms and Brinell stops being comparable; below 20 HRC the diamond cone leaves its range; above 100 HRB the 1/16" ball is no longer reliable either. The tool tells apart leaving the table from leaving the test, which is not the same thing.

Because an exact number would be false. ASTM E140 states in clause 6.2 that, given the variation between materials, it is not possible to state confidence limits for the error when using a conversion table. The only scatter the standard publishes is that of table 6, for austenitic sheet. The ± you see is the order of magnitude the shop works with, not a standard figure, and chaining two conversions multiplies it.

A thin sheet, no: below 1.6 mm the HRC feels the anvil underneath and the reading comes out high; there you go to superficial Rockwell (15N, 30N) or Vickers. And on a case-hardened, nitrided, induction-hardened or coated part, the conversion means nothing: the indenter goes through case and core at once. That is measured as microhardness on a cross-section, and you talk about a depth profile, not a single number.

Yes, and that is not a correlation: these are the definitions of the tests themselves, so the result is exact. Enter load, ball and indent diameter and you get HBW; with the diagonal you get HV or HK. It also checks that the indent falls between 24 and 60 % of the ball diameter and that the F/D² ratio is a standard one, which is what makes two tests comparable: 3000 kgf with a 10 mm ball and 187.5 with a 2.5 mm ball give the same number because both are 30.

Yes. Search by family, EN or AISI (e.g. C45, 42CrMo4, 1.2344) and we load the typical datasheet hardness. If there are several (as-supplied and hardened/case-hardened), you choose which to use. From there you link to the equivalences sheet and to Vc parameters when the material has cutting data.