Swivel coupler

A coupler whose two jaws rotate on a rivet, joining two 48.3 mm tubes at any angle – the standard fitting for tube diagonals and raking braces.

Also called: swivel clamp, swivel, rotating coupler, angle coupler

A scaffold only stands firm once it gets a triangle somewhere. Rectangular bays alone can fold sideways; an inclined brace makes them rigid. This is where the swivel coupler comes in. Its two jaws are joined by a rivet that lets them turn, so two tubes can be clamped together at any angle.

Typical uses are tube diagonals: a cross brace in a frame bay, bracing under a compensation frame or a strut under a bracket. At building corners it is indispensable too – two frames meeting at a corner are often joined directly with two swivel couplers, one just below the deck transom and one at the bottom.

Design

From the outside it resembles the right-angle coupler: two jaws with hinged caps, each closed by bolt and nut, in zinc-plated steel, with a 22 mm or sometimes 19 mm spanner size. The difference is in the middle – instead of a rigid centre piece there is a pivot, and the jaws turn freely through 360 degrees until the nuts are tightened.

• Standard: covered by EN 74-1; for load-bearing diagonals instructions usually require class B.
• Special forms: swivels with one jaw for another tube diameter, or couplers with a wedge connection for the rosette of a modular scaffold.
• Limitation: because the joint can rotate, it transmits no twisting between the tubes. It stops tubes slipping but does not make a cross into a stiff node. Where a rigid right angle is called for, use a right-angle coupler.

Fitting a tube diagonal

1. Check that the pivot moves easily without wobble.
2. Place the first jaw on the load-bearing tube – usually the upright – as close as possible to the node and nip it up lightly.
3. Lay the diagonal in the second jaw, set the angle and line the tube up with the opposite point.
4. Leave enough tube beyond the coupler; at least 40 mm is often required.
5. Only when both ends are in place tighten all nuts to 50 Nm.
6. Check: the diagonal must not sag, and the couplers belong at the nodes, not somewhere mid-bay.

When dismantling, the diagonal comes off last – only once the bay above has gone or stays otherwise secured. Removing bracing too early takes away the scaffold's hold.

What to check

• Distance from the node: the further the coupler sits from where upright and ledger cross, the more the tube bends. Close is the rule.
• Not a substitute for a right-angle coupler where a rigid angle is required.
• Play in the pivot: a worn swivel whose jaws rock noticeably is rejected.
• Threads: clean, lightly greased threads reach torque reliably.
• Buying used: check the marking, inspect the rivet for cracks and run every bolt through once by hand. Bent caps or squashed jaws are no bargain.

On systems with ready-made braces, such as the vertical diagonal, a tube and swivel couplers replace them only where the instructions expressly allow it. Used swivels are listed under couplers.