Accumath Toolchest — Hardness Conversion Dataset: Notes

Dataset file: accumath-hardness-conversion.csv Built: 2026-10-20

⚠️ READ FIRST — these conversions are APPROXIMATE by nature

Hardness is not a single fundamental physical property, and no exact conversion between hardness scales exists. Every number in this dataset is an empirical approximation, valid only in an average sense for the material class stated below. ASTM E140 itself — the standard this relationship comes from — states that its conversion tables are approximate, that converted values must not be used in place of a measurement in the specified scale for acceptance or referee purposes, and that conversions should be avoided for specification limits whenever the specified scale can be measured directly. The approximate tensile strength column is the roughest of all: it is a correlation, not a measurement, and different published charts differ materially at high hardness (see Cross-check). Use this dataset for comparison, screening, and sanity checks — never as the sole basis for accepting or rejecting material.

Material scope

Non-austenitic steels only — the ASTM E140 Table 1 relationship: carbon steels, alloy steels, and tool steels in the hardened, tempered, normalized, or annealed condition. Do not apply these conversions to austenitic stainless steels, cast irons, or non-ferrous alloys; E140 publishes separate, different tables for those (austenitic steels work-harden under the indenter and follow a visibly different relationship).

Source

Primary (the table transcribed): S&G Global Fastening Solutions, "Hardness Conversion Tables" — an openly published producer chart presenting the ASTM E140 Table 1 / Table 2 relationship for non-austenitic steels, with the approximate tensile strength columns in the ASTM A370 / SAE J417 tradition. Downloaded 2026-10-20 from the publisher's site (www.sgglobal.in).
Values are transcribed as published — no interpolation between rows, no computed conversions between unit columns (the chart prints MPa and ksi itself; both are reproduced). The ASTM E140 standard document itself was not used as a source (it is a paywalled standard); the values are the published facts of the producer chart, with the source named on every row.

Coverage

86 rows: Rockwell C block — HRC 20–68 in 1-point steps (49 rows); Rockwell B block — HRB 96 down to 60 (37 rows).
The HRC 20–24 rows also carry their HRB equivalents (HRB 97–101) exactly as the chart prints them on the same rows, so HRB 97–100 coverage is on those rows; the chart likewise prints HRB equivalents above 100 beside HRC 48–55 (116–120), reproduced as printed.
Below HRC 20 the source chart prints nominal C-scale figures down to 0; those are outside the E140 Table 1 range and are not reproduced — the lower block is keyed by HRB, per E140 Table 2 practice.
The source chart continues past the dataset at both ends (to HRC 70 and to HRB 0). The dataset extracts HRC 20–68 and HRB 60–100 as specified; below HRB 60 the chart's Brinell column changes basis (500-kgf load values) and its Vickers column is empty, so HRB 60 is the natural cut-off.

Columns

Column	Meaning
HRC	Rockwell C hardness (diamond cone, 150 kgf) — row key for the upper block
HRB	Rockwell B hardness (1/16 in ball, 100 kgf) — row key for the lower block
HBW	Brinell hardness number, 10 mm ball, 3000 kgf, as printed in the source chart (see ball note below)
HV	Vickers hardness number
HRA	Rockwell A hardness (diamond cone, 60 kgf)
HRD	Rockwell D hardness (diamond cone, 100 kgf)
HS	Shore scleroscope hardness
approx_tensile_MPa	Approximate tensile strength, MPa (N/mm²) — see warning above
approx_tensile_ksi	Approximate tensile strength, ksi — as printed (the chart's own rounding)
source	The published chart transcribed

Brinell ball note: above roughly 450 HB a steel ball itself flattens, so E140 prints tungsten-carbide-ball (HBW) values in the upper range. The source chart's single Brinell column matches the carbide-ball values exactly at HRC 56–65 and at most rows at and below HRC 47, but in the HRC 48–55 band it tracks the slightly lower standard-ball values (see Cross-check). The column is reproduced as the chart prints it; treat Brinell figures in the 450–560 band as carrying that few-points ambiguity in addition to the general approximation warning.

Blank cells are as published: the chart gives no Brinell value above HRC 65, no tensile strength above HRC 60, no tensile or Shore values below HRB 80/81, and no Vickers values below HRB 81. Nothing was filled in.

Cross-check (second and third published tables)

Checked against: (a) Eklavya Tech's published abridgment of ASTM E140 Table 1 (HV, carbide-ball HBW, HRA, tensile MPa), and (b) ZIPP Gear's published hardness conversion chart (HV-indexed; HRA, HRD, Shore), plus a DIN 50150-based chart for one HRB row. Ten HRC rows checked in full (68, 65, 60, 55, 52, 50, 45, 40, 35, 30, 25, 20 — twelve spot rows):

HV, HRA, HRD, HS: exact agreement at every checked row. Examples — HRC 68: HV 940, HRA 85.6, HRD 76.9, HS 97 in all sources. HRC 60: HV 697, HRA 81.2, HRD 70.7, HS 81 in all sources. HRC 20: HV 238, HRA 60.5 in both tabular sources.
HBW: exact agreement at most rows (e.g., 654 @ HRC 60, 421 @ 45, 371 @ 40, 286 @ 30, 253 @ 25), differing in one band: against the second source's carbide-ball column, the primary chart reads lower by 4 @ HRC 20 (222 vs 226), 4 @ HRC 48 (451 vs 455), 6 @ HRC 50 (475 vs 481), and 12 @ HRC 52 (500 vs 512) — consistent with the ball note above. No other HB disagreements found.
Approximate tensile strength: agreement in the working range, divergence at high hardness. HRC 30: 965 MPa in both. HRC 40: 1255 vs 1250 MPa. HRC 45: 1420 vs 1480 MPa. HRC 55: 1889 vs 2075 MPa. The second source keys tensile to the HRC scale (SAE J417 style); the primary chart's tensile tracks the Brinell number (ASTM A370 style). Both conventions are published and in industrial use; the dataset reproduces the primary chart and flags the divergence here rather than silently picking a winner.
HRB row check (DIN 50150-based chart): HRB 98 → HB 228 agrees exactly (HV 243 in the primary chart vs 240 in the DIN-based chart — within chart rounding/indexing).

Conclusion: the dataset's hardness-scale columns (HV, HRA, HRD, HS) are corroborated exactly by independent published tables; the Brinell column is corroborated except for the documented ball-basis band; the tensile column is corroborated at ordinary hardness and carries a documented, source-dependent spread at high hardness — one more reason it is labeled approximate.

Legal basis — published facts, source named

The values are standardized conversion facts as published in an openly published producer chart, recorded into Accumath's own table structure with the publisher named on every row. No part of the ASTM E140 standard document was copied, and no expressive text from any source is reproduced. Position (Jeff, 2026-10-20): publicly published data is public; facts do not require licensure.