Source: https://guthlabs.ai/docs/instruments/hardness-scale-converter-hrc-hb-hv-hrb-mohs/

instrument / verified-clean

# Hardness Scale Converter (HRC/HB/HV/HRB/Mohs)

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/hardness-scale-converter-hrc-hb-hv-hrb-mohs/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/hardness-scale-converter-hrc-hb-hv-hrb-mohs/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/hardness-scale-converter-hrc-hb-hv-hrb-mohs/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/hardness-scale-converter-hrc-hb-hv-hrb-mohs/qualification/>)

## Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

**Area**: Chemistry & Materials

**Tranche**: tranche-7

**Evidence ID**: t7-014

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The steel HRC/HB/HV vectors are valid lookup-table tests using commonly reproduced ASTM E140 steel values, with the third vector explicitly testing linear interpolation. The Mohs vector is a boundary and rejection test: Mohs 10 is a standard table entry, but ASTM E140 supplies no universal conversion from it. The implementation needs a versioned table source, explicit material classes, valid ranges, interpolation policy, and a separate documented tensile-strength convention before it can be labeled as a complete converter.

### Formula and scope findings

- ASTM E140 provides conversion tables for specified hardness scales and material groups, but it does not provide a universal Mohs-to-Rockwell/Brinell/Vickers conversion; Mohs conversion must be rejected or supported by a separately identified material-specific table.

- The specification names steel-specific ASTM E140 data but also accepts arbitrary material classes; tables for non-steel alloys and the allowed material-class values are not defined.

- Interpolation is not specified. Linear interpolation between tabulated points is a reasonable engineering approximation, but it must be explicitly labeled as an interpolation convention rather than an exact ASTM result.

- Approximate tensile strength is not determined by a universal hardness formula. It requires a clearly identified steel-only correlation/table, with applicable composition and hardness-range limits.

- HRB and HRC ranges, test-force conventions, and handling of conversions outside the valid ASTM E140 ranges are unspecified.

### Unit assumptions

- Hardness values are dimensionless scale readings: HRC, HRB, HB, HV, and Mohs must retain their scale labels; they are not interchangeable physical units.

- Tensile strength, when supplied, is reported in MPa.

- The steel conversion fragments below use the commonly reproduced ASTM E140 steel table convention; exact values can vary by ASTM edition, table, alloy, and rounding convention.

- Linear interpolation is performed on the numerical hardness values and on the tabulated tensile-strength estimates.

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

The principal breaks are out-of-domain hardness values that must be rejected rather than interpolated, plus ambiguity when a bare hardness number or tensile-strength unit is supplied. A lookup engine that silently extrapolates HRC 0 or HRC 1,000,000, or assumes an unlabeled scale, can return materially misleading results.

## Errata and corrections

No applied erratum is attached to this unique-name record.

## Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

````
{
  "inputs": {
    "hardness_value": 30,
    "input_scale": "HRC",
    "material_class": "steel"
  },
  "expected_outputs": {
    "HRC": 30,
    "HB": 286,
    "HV": 302,
    "approx_tensile_strength_MPa": 1010
  },
  "reference_data": {
    "table_type": "Rockwell C to Brinell/Vickers/tensile strength, steel",
    "HRC_30": {
      "HB": 286,
      "HV": 302,
      "approx_tensile_strength_MPa": 1010
    },
    "source_convention": "ASTM E140 steel conversion table convention, widely tabulated standard value"
  },
  "working": "Input is exactly the HRC 30 row. Therefore HRC = 30, HB = 286, and HV = 302 with no interpolation. The steel-table tensile estimate is 1010 MPa."
}
````

## Related workflows

No source-defined multi-instrument workflow membership is recorded.

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`

- `evidence-tranche7/tranche7-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`