For hexagon coupling nuts, DIN 6334 defines the dimensions, tolerances and product grades. The sections below describe the scope of the document, the properties it deliberately leaves to companion standards, and the equivalent designations across standards bodies.
DIN 6334 — Scope
DIN 6334 specifies the dimensions and tolerances of hexagon coupling nuts. 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
DIN 6334, alongside the related DIN 6334 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 DIN 6334
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e (mm) | Length l (mm) | Reference standard |
|---|---|---|---|---|---|
| M6 | 1.0 | 10 | 11.05 | 18 | DIN 6334 |
| M8 | 1.25 | 13 | 14.38 | 24 | DIN 6334 |
| M10 | 1.5 | 17 | 18.90 | 30 | DIN 6334 |
| M12 | 1.75 | 19 | 21.10 | 36 | DIN 6334 |
| M14 | 2.0 | 22 | 24.49 | 42 | DIN 6334 |
| M16 | 2.0 | 24 | 26.75 | 48 | DIN 6334 |
| M18 | 2.5 | 27 | 29.56 | 54 | DIN 6334 |
| M20 | 2.5 | 30 | 33.53 | 60 | DIN 6334 |
| M22 | 2.5 | 32 | 35.03 | 66 | DIN 6334 |
| M24 | 3.0 | 36 | 39.98 | 72 | DIN 6334 |
| M27 | 3.0 | 41 | 45.20 | 81 | DIN 6334 |
| M30 | 3.5 | 46 | 50.85 | 90 | DIN 6334 |
| M33 | 3.5 | 50 | 55.37 | 99 | DIN 6334 |
| M36 | 4.0 | 55 | 60.79 | 108 | DIN 6334 |
Companion Standards
DIN 6334 controls only the geometry of hexagon coupling nuts. 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 DIN 6334
DIN 6334 is still widely used in European mechanical engineering and as a cross-reference on legacy drawings; its ISO equivalent is preferred for new designs.
