A wind turbine bolt specification is a short string of standard numbers — DIN 933, ISO 898-1, EN 14399, EN 10204 3.1. Each one controls a different attribute of the fastener. Knowing which standard governs what turns an intimidating callout into a precise, checkable order.
§ 01 DIN, EN and ISO — how they relate
Three families of standard appear on European wind fastener drawings, and they overlap by design:
- DIN — original German standards. Many classic dimension standards (DIN 933, DIN 931) are still quoted by habit even though they have been superseded by ISO equivalents.
- EN / EN ISO — European norms; for fasteners these are largely the adopted ISO standards (e.g. EN ISO 4017 = the old DIN 933).
- ISO — the international root standard most EN documents are based on.
In practice DIN and EN ISO numbers are often used interchangeably for the same part — a key point when reconciling old and new drawings.
§ 02 Standards for dimensions
| Old DIN | Current EN ISO | Part |
|---|---|---|
| DIN 933 | EN ISO 4017 | Fully threaded hex bolt |
| DIN 931 | EN ISO 4014 | Part-threaded hex bolt |
| DIN 934 | EN ISO 4032 | Hex nut |
| DIN 125 | EN ISO 7089 | Plain washer |
| DIN 6914 | EN 14399-4 | Structural (HV) hex bolt |
§ 03 Standards for mechanical properties
Dimensions tell you the shape; a separate standard sets the strength. For carbon/alloy steel that is ISO 898-1 (bolts) and ISO 898-2 (nuts) — the property class system explained in ISO 898-1 property classes and what the property class means. For stainless, the equivalent is ISO 3506 (A2-70, A4-80).
§ 04 Structural bolting, coatings and documents
- Structural preloaded bolting — EN 14399 (HR/HV systems) in Europe; the comparison with the US ASTM A490 system is in EN 14399 vs ASTM A490.
- Coatings — ISO 10683 (zinc flake), ISO 4042 (electroplating), and hot-dip galvanizing standards; see HDG vs zinc flake.
- Inspection documents — EN 10204 defines the 3.1 certificate; see material traceability.
- Corrosivity — ISO 12944 / ISO 9223 define the C1–CX categories.
§ 05 Reading a full callout
Putting it together, a complete wind-fastener callout layers the standards: a dimension standard, a property class, a coating standard, and a documentation requirement — for example "EN ISO 4014 M42 × 200 — 10.9 — Geomet 500B (ISO 10683) — EN 10204 3.1". Each token is independently verifiable, which is exactly what makes a specification auditable. Build your RFQ the same way and a supplier can confirm every element on the first reply — see choosing a supplier.