Doughty Gravlock Couplers — Steel Girder Clamps for 48mm Tube The Doughty Gravlock Couplers are heavy-duty steel clamps designed to attach standard 48mm tube directly to the flange of a steel I-beam or RSJ at 90° — creating a secure, load-rated fixing point without drilling, welding, or modifying the structure. Used in theatres, studios, arenas, and live event venues where there is no grid or ceiling track, they allow riggers to hang lighting bars and truss directly from the building's structural steelwork. With a WLL of 600kg per pair and S275 mild steel construction with Grade 8.8 fixings, they are built for permanent and semi-permanent installations where reliability is critical. Must be used in pairs — sold as a pair. Also available as a Gravlock Swivel Coupler for installations where the tube needs to run at a different angle to the beam. Key Features: WLL 600kg per pair — heavy-duty load rating for permanent structural installations Attaches 48mm tube to steel I-beam and RSJ flanges at 90° — no drilling or welding required Fits flanges up to 45mm (1.77") — compatible with standard structural steel sections S275 mild steel construction with Grade 8.8 fixings — high strength and durability M16 x 80 bolts with 1/2" BSW 12 TPI thread — minimum tightening torque 54Nm Passivate finish — corrosion resistant, colour may vary Must be used in pairs — sold as a pair (T29497) British designed and manufactured by Doughty Engineering Compatible Accessories: Doughty Gravlock Swivel Coupler — 360° swivel variant for angled installations Doughty Safety Bonds — mandatory secondary fixing for all overhead rigged equipment Doughty Clamps & Couplers — full range of aluminium and steel clamps Rigging Hardware — shackles, pulleys and rigging accessories Browse our full range of Doughty steel clamps, Doughty Engineering products and entertainment and stage rigging at MTN Shop.
