Key Clamp Adjustable Knuckle 0 to 120 Degrees for 48.3mm Tube, Galvanised

The adjustable knuckle joins two tubes of the same size at any angle from straight round to 120°, so a level rail can run into a sloping one without bending the tube. Each tube end pushes into its own socket and is locked with a grub screw, and the knuckle in the middle is set at the angle you need and secured with its setscrew. It suits 48.3mm outside diameter tube and is malleable cast iron with a galvanised finish for indoor and outdoor use. The price shown is for one fitting.

Why use an adjustable knuckle

No tube bending. A rail changing from level to a slope normally needs a bending machine or a welded joint. The knuckle does it on site with a hex key.

Set to the real angle. Ramps and steps are rarely exactly as drawn. The knuckle is set to suit what is there, then locked.

Closed tube ends. Both tubes finish inside the fitting, leaving no sharp edge at the change of direction.

Galvanised for outdoors. The zinc coating protects the iron on ramps, steps and walkways in all weathers.

Where it is used

Top rails where a level run meets a ramp or stair, changes of slope on handrails, sloping braces on tube frames, and any joint between two tubes of the same size where the angle is set on site.

Specifications

Letters refer to the dimension drawing above. Dimensions are for guide only and may vary slightly.

Know its limits

It joins two tubes of the same size only. No load rating is published, so for a guard rail that must meet a set load, ask a structural engineer to check the design.

How many do you need?

One at each change of direction. A rail that runs level, down a ramp and level again needs two.

Choosing the right size

Key clamps are sized by the tube's outside diameter. 48.3mm is standard scaffold tube, often sold as 1½" or 40mm nominal bore. Measure across the tube before ordering: this fitting will not grip 42.4mm or 60.3mm tube. The same galvanised fitting is made for 33.7mm and 42.4mm tube.

Setting the angle

Push each tube into its socket and set the knuckle to the angle the rail needs, anywhere from 0 to 120 degrees. Tighten the setscrew that holds the knuckle and the grub screw in each socket, then check the angle again, because a long rail can pull the joint slightly as it is locked.

Fitting and care

Cut the tube ends square and deburr them. Push each one fully into its socket, set the angle, then tighten the knuckle setscrew and both grub screws firmly with a 5/16" hex key. Check the screws after the first week and once a year after that. Touch up scratched galvanising with zinc-rich paint.

Frequently asked questions

Ordering and delivery

Order online, with Express UK Delivery to your site and same-day dispatch on orders before 2pm, Monday to Friday. For a full rail kit, call 01744 520 110 or email sales@industrialsuppliesco.co.uk and we will confirm availability and delivery before you order.