080M40 equivalent grades: ASTM, EN, JIS, GB, DIN
080M40 is unalloyed medium-carbon engineering steel (British standard) specified in BS 970. The cross-reference runs across 2 standard systems and grades every candidate, so the reason a substitution is safe is on the same row as the name. The full 080M40 data sheet carries the composition and mechanical tables.
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C45 differs on one limit only — a carbon ceiling, an impact temperature or a strength minimum. 1045, 42CrMo4 serve the same purpose without being the same steel, so a substitution there needs the design re-checked rather than the certificate. Across systems that is 2 in EN (European), 1 in AISI / SAE.
Cross-reference table
| Grade | System | Match | Why / differences |
|---|---|---|---|
| C45 | EN (European) | Near | C45 (1.0503) is 0.42–0.50 % C against 080M40's 0.36–0.44 %, so it sits slightly above — closer to 080M46. For general shafting the substitution is routine, but C45 will through-harden marginally deeper and machine marginally harder. |
| 1045 | AISI / SAE | Functional | AISI 1045 is 0.43–0.50 % C — the American counterpart of 080M46. Against 080M40 it is one carbon step higher; AISI 1040 is the true match, at 0.37–0.44 % C. |
| 42CrMo4 | EN (European) | Functional | The alloy step up, equivalent to 709M40 (EN19). Substitute where hardenability in sections above about 60 mm or genuine toughness is required — 080M40 cannot deliver either. |
Identical, near and functional are defined once on the grade index; the reason column below says which limit differs in each case.
080M40 in EN (European)
- C45 — Near C45 (1.0503) is 0.42–0.50 % C against 080M40's 0.36–0.44 %, so it sits slightly above — closer to 080M46. For general shafting the substitution is routine, but C45 will through-harden marginally deeper and machine marginally harder.
- 42CrMo4 — Functional The alloy step up, equivalent to 709M40 (EN19). Substitute where hardenability in sections above about 60 mm or genuine toughness is required — 080M40 cannot deliver either.
080M40 in AISI / SAE
- 1045 — Functional AISI 1045 is 0.43–0.50 % C — the American counterpart of 080M46. Against 080M40 it is one carbon step higher; AISI 1040 is the true match, at 0.37–0.44 % C.
Superseded names for 080M40
- En8 — BS 970:1955 (withdrawn): The name almost everyone still uses. En8 became 080M40 in the 1970 revision, and more than half a century later the old name has not gone away — suppliers, drawings and stock lists across Britain, Ireland, India, Australia and the Gulf all still say EN8.
- En8D — BS 970:1955 (withdrawn): The letter suffix marked a tighter sulphur and phosphorus limit for better ductility; closest modern equivalent is 080A40 ordered to analysis.
- 080M46 — BS 970-1: The next grade up in the same family: 0.42–0.50 % carbon, the British counterpart of AISI 1045 rather than 1040. Frequently confused with 080M40 in cross-reference tables.
Key data for 080M40
Full composition, mechanical properties by thickness, heat treatment and applications for 080M40 →
Verified against BS 970-1:1991. Last checked: September 2026.