The Next Generation
Earthing Nut

An earthing nut is a specialist brass fitting used with SWA (Steel Wire Armoured) cable glands to establish a reliable, low-impedance connection between a cable's steel armour and the installation's protective earthing system. It replaces the traditional banjo washer and separate earth tag with a single machined component that is faster to install, easier to inspect and more mechanically stable over the life of the installation.

In a modern SWA earthing nut design, the nut threads directly onto the outer portion of the SWA gland body. A dedicated conductor entry accepts the protective earth conductor, which is clamped in place by stainless grub screws to a specified torque. The result is a repeatable, torque-verified termination that maintains full 360° contact with the gland body — the ideal geometry for a low-impedance armoured cable earthing bond.

Brass earthing nuts are the industry preference because brass combines excellent conductivity with strong mechanical properties and long-term corrosion resistance. CZ121 brass in particular is dimensionally stable under repeated tightening cycles, resistant to galvanic corrosion when mated with brass glands, and holds a stable low-impedance contact for the full service life of the installation — the qualities that separate a premium cable gland earthing nut from a generic stamped part.

An earthing nut is required because BS 7671, the IET Wiring Regulations, demands that the metallic armour of an SWA circuit is effectively bonded to the protective earthing system with a connection that is mechanically reliable and electrically continuous. Without a solid earth bond, a fault could energise the cable armour, gland body and any connected metallic enclosure — with obvious consequences for safety. A properly torqued brass earthing nut provides the deliberate, low-resistance path that lets protective devices operate quickly and reliably.

Typical applications for an earthing nut span the full range of professional electrical installations: industrial manufacturing plants, commercial fit-outs, data centres, control panels, distribution boards, rail infrastructure, renewable energy installations and OEM panel builds. Anywhere SWA cable terminates into a metallic enclosure, SWA accessories such as the earthing nut are the interface that transfers fault current from the armour, through the gland and into the earth conductor with minimum impedance.

Beyond safety, a well-executed earth bond is also critical for EMC performance. High-frequency interference on the SWA armour must be diverted to earth rather than radiated into surrounding equipment, and only a consistent 360° bond — the kind produced by a precision machined earthing nut — will maintain that path over time. The VOLTLOK® cable gland accessories family is engineered around this principle, delivering protective earthing and EMC bonding in a single, integrated component.

Compared with legacy hardware, a premium earthing nut removes the ambiguity of a hand-fabricated banjo bond. There is no washer to lose, no earth tag to misalign, and no risk of a loose thread or missed torque. For the professional electrician, that means faster installation, cleaner terminations and a more reliable electrical earthing system — every job, every gland, every time.