How this calculator works
Regular Rockwell hardness uses the permanent penetration increase after removing the major load while retaining the preliminary load. B and C scales have different indenters and total forces; both use 0.002 mm per hardness point. Conversion mode linearly interpolates four published non-austenitic steel reference points over HRC 20 to 50. It is a coarse estimate between anchors, not an exact relationship or a full ASTM table. Other alloy families require their own validated conversion data and are deliberately excluded. Direct depth calculation is independent of the steel conversion.
Formula
HR = N - h/(0.002 mm), with N = 100 for HRC and 130 for HRB. Steel conversion uses bounded piecewise linear interpolation between stated reference points.
Worked example
A permanent penetration increase of 0.1 mm gives HRC 50 or HRB 80, depending on the test scale. The steel conversion reference maps HRC 40 to approximately HV 392 and HB 371.
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Frequently asked questions
Can I convert any metal with this steel table?
No. Hardness correlations depend on material family and condition. This conversion is limited to non-austenitic steels.
Is depth measured under the full major load?
Use the permanent differential depth after major-load removal, with the preliminary load still applied.
Are converted results suitable for acceptance testing?
Use the required hardness test or the conversion procedure permitted by the governing specification. Interpolated estimates do not replace it.