ISO 4034 is the international standard for hex nuts, grade c. This page sets out what the standard governs, the size range it specifies, and the related standards you will see referenced in datasheets.
ISO 4034 — Scope
ISO 4034 specifies the dimensions and tolerances of hex nuts, grade c. Material, property class, surface finish and packaging are governed by separate documents in the same standards family (for example ISO 898-1 for the mechanical property classes of bolts and screws).
Tolerance & Product Grades
ISO 4034, alongside the related ISO 4034 entries on this site, specifies product grades (typically A or B for fine work and C for general engineering) and tolerance classes for the controlling dimensions. Choose the grade against the precision your application requires.
Dimensions Specified by ISO 4034
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e min (mm) | Nut height m (mm) | Product grade | Reference standard |
|---|---|---|---|---|---|---|
| M5 | 0.8 | 8.0 | 8.63 | 4.7 | Grade C | ISO 4034 / DIN 555 |
| M6 | 1.0 | 10.0 | 10.89 | 5.2 | Grade C | ISO 4034 / DIN 555 |
| M8 | 1.25 | 13.0 | 14.2 | 6.8 | Grade C | ISO 4034 / DIN 555 |
| M10 | 1.5 | 17.0 | 18.72 | 8.4 | Grade C | ISO 4034 / DIN 555 |
| M12 | 1.75 | 19.0 | 20.88 | 10.8 | Grade C | ISO 4034 / DIN 555 |
| M14 | 2.0 | 22.0 | 24.49 | 12.8 | Grade C | ISO 4034 / DIN 555 |
| M16 | 2.0 | 24.0 | 26.75 | 14.8 | Grade C | ISO 4034 / DIN 555 |
| M18 | 2.5 | 27.0 | 29.56 | 15.8 | Grade C | ISO 4034 / DIN 555 |
| M20 | 2.5 | 30.0 | 33.53 | 18.0 | Grade C | ISO 4034 / DIN 555 |
| M22 | 2.5 | 32.0 | 35.72 | 19.4 | Grade C | ISO 4034 / DIN 555 |
| M24 | 3.0 | 36.0 | 39.55 | 21.5 | Grade C | ISO 4034 / DIN 555 |
| M27 | 3.0 | 41.0 | 45.2 | 23.8 | Grade C | ISO 4034 / DIN 555 |
| M30 | 3.5 | 46.0 | 50.85 | 25.6 | Grade C | ISO 4034 / DIN 555 |
| M36 | 4.0 | 55.0 | 60.79 | 31.0 | Grade C | ISO 4034 / DIN 555 |
| M42 | 4.5 | 65.0 | 71.3 | 34.0 | Grade C | ISO 4034 / DIN 555 |
| M48 | 5.0 | 75.0 | 82.6 | 38.0 | Grade C | ISO 4034 / DIN 555 |
Companion Standards
ISO 4034 controls only the geometry of hex nuts, grade c. The mechanical strength is set by ISO 898-1 (bolts and screws) or ISO 898-2 (nuts); the surface finish is governed by separate finish standards (e.g. ISO 4042 for electroplating). For corrosion testing, the relevant document is ISO 9227 (neutral salt spray).
When to Specify ISO 4034
Choose ISO 4034 for international engineering work and OEM supply where ISO standards are the contractual reference. It is the default modern specification for hex nuts, grade c.