DIN 6334 Hexagon Coupling Nuts

DIN 6334 Hexagon Coupling Nuts are elongated, internally threaded fasteners used to connect two threaded rods, studs, or other externally threaded components. They are commonly known as hexagon coupling nuts, long coupling nuts, or extension nuts. Unlike a standard hex nut, the extended body provides sufficient internal thread length for connecting separate threaded components while retaining an external hexagonal profile for wrench installation. DIN 6334 defines the dimensional form of this type of elongated hexagon nut.

The standard dimensional series covers common metric sizes such as M6 through M36. The overall nut length follows an elongated proportion, with examples including M12 × 36 mm, M16 × 48 mm, M20 × 60 mm, and M24 × 72 mm. The hexagonal width across flats increases with the nominal thread diameter, allowing conventional wrench engagement during assembly. The internal thread is commonly specified with a 6H tolerance class.

These coupling nuts are used where two threaded components need to be joined or where additional threaded length is required within an assembly. Typical applications include threaded rod connections, suspended support systems, mechanical assemblies, fabrication equipment, mounting structures, and general industrial fastening. Their elongated form also makes them useful where greater thread engagement is required than a conventional hexagon nut can provide.

DIN 6334 coupling nuts are available commercially in carbon steel and stainless steel versions, with material and property class selected according to the required mechanical and environmental conditions. For carbon and alloy steel nuts, mechanical properties may be specified in accordance with ISO 898-2 where applicable.