Fittings
What is a double coupler?
A double coupler joins two scaffold tubes at right angles and is the only coupler rated to carry load in a scaffold structure. It is what connects ledgers to standards.
Use this diagram+
Free to use on your own site, in training material or in a course handout, as long as the credit link stays on it. Paste this where you want the diagram to appear.
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<img src="https://scaffoldoptix.co.uk/glossary/double-coupler/diagram.svg" alt="double coupler — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
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<a href="https://scaffoldoptix.co.uk/glossary/double-coupler">What is a double coupler?</a> — diagram by
<a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
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</figure>Also called a right angle coupler. It is the structural fitting of a tube and fitting scaffold: where load has to pass from one tube to another, this is the coupler that does it.
That is the distinction worth holding on to. A swivel coupler joins tubes at any angle but is not rated for the same duty, so substituting one for the other at a load-bearing connection changes the structure whether or not it looks the same.
Doubles are tightened to a specified torque. The performance the design assumes comes from the fitting being installed as intended, not from it merely being closed.
What goes wrong on site
- A swivel used where a double is required, because it was what came to hand on the lift.
- Couplers nipped up by feel rather than torqued.
- Worn or distorted couplers left in service because they still close.