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.
Wind turbine fastener callouts typically combine three standards: ISO 898-1 (property class — 8.8/10.9/12.9), EN 14399 (structural preloaded bolt sets — HV/HR system), and EN ISO 4014/4017 (dimensional — hex bolt geometry). For stainless: ISO 3506. Coatings are governed by ISO 10684 (hot-dip galvanising) or EN ISO 12683 (zinc flake). The MTC (EN 10204) is the quality document. A compliant callout specifies all four layers.
- Best for
- Engineers interpreting wind turbine fastener specifications or writing purchase orders who need to know which standard governs each requirement
- Not suitable for
- Non-structural fasteners (cable clips, cover fixings) where informal grade 8.8 zinc-plated is typically adequate and full structural callout is over-engineered
- Selection steps
- 1 — Identify joint type (structural/secondary) → 2 — Select property class standard (ISO 898-1 or ISO 3506) → 3 — Confirm dimensional standard → 4 — Specify coating standard → 5 — State MTC level required (EN 10204 2.1 or 3.1)
- RFQ information
- Property class, diameter and pitch, length, coating specification, MTC level, quantity, delivery requirement
§ 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 Many classic dimension standards (DIN 933, DIN 931) are still quoted by habit even though they have been superseded by ISO equivalents.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.
Evidence and decision boundary
- Direct evidence
- The cited standards define properties, tests or joint-design requirements within their stated scopes; they do not authorize replacement of a wind-turbine fastener by diameter or property class alone.
- Engineering inference
- Assess the complete assembly: load and fatigue, geometry, thread, nut/washer, preload, friction/coating, installation, inspection and the controlling OEM drawing.
- Typical or indicative value
- Torque, preload percentage, class equivalence and inspection intervals are indicative until validated for the approved joint.
Primary sources checked
- ISO 898-1:2013 - metric fastener property classes
- ISO 16047:2005 - torque/clamp-force testing
- IEC 61400-6:2020+A1:2025 - tower and foundation design
Related commercial route: Compare wind-turbine clamp systems and RFQ inputs.