Sleeve coupler and spigot

Parts that extend tubes and standards in a straight line: the spigot or joint pin centres from inside, the sleeve coupler clamps from outside.

Also called: joint pin, spigot, spigot pin, tube connector, end-to-end coupler

No tube is ever exactly as long as you need. Whether a standard is carried further up or a long tube is extended as a rail or ledger, at some point two tube ends meet. That joint has to hold the tubes in line and, depending on its position, transmit compression or even tension.

Two solutions are often confused. The spigot – called a joint pin in the UK when it is a loose expanding part – sits inside the tube and centres both ends. The sleeve coupler grips the ends from outside and clamps them with bolts. In practice the two are often combined.

Variants

• Pressed-in spigot: the standard of a modular scaffold usually has a short tube pressed into its top. The next standard simply slides over it. Many frame systems use welded-in spigots on the frame uprights for the same purpose.
• Loose spigot: a short tube piece, often with a central stop, pushed into two tubes. It keeps them aligned but transmits practically only compression.
• Drilled spigot: can be secured against pulling apart with bolts or pins where a joint must resist tension.
• Sleeve coupler: an elongated coupler with two clamping zones, covered by EN 74-1, placed over both ends; many manufacturers approve it only together with an internal spigot.
• Tension coupler: internal connector plus external clamp, designed to take tension.

Making the joint

1. Check both ends are straight, round and clean inside.
2. Push the spigot in to its stop, or with pressed-in spigots slide the upper tube fully home.
3. Make sure the end faces bear on each other with no gap.
4. Centre a sleeve coupler over the joint and tighten the nuts to 50 Nm.
5. Where the instructions require a tension-proof joint, fit the bolt, locking pin or screw.
6. Place joints near nodes and stagger neighbouring ones so not all tubes end at one level.

For dismantling remove the locking first, then pull the upper tube off upwards – never lever it, or the spigot bends.

When must a joint resist tension?

Normally the scaffold's own weight presses standards together and a plain push-fit is enough. It is different when wind tugs at nets or sheeting, when the top lift stands free above the last tie, on suspended structures, or when parts are lifted by crane. Then standards can be pulled apart, and the instructions specify where pins and clips are needed.

What to check

• A tube standing crooked reveals a bent spigot – replace it.
• A pressed-in spigot must be straight and tight with no wobble.
• Open tube ends and spigots are not anchor points for fall-arrest equipment – the karabiner can slip off.
• Do not use a sleeve coupler on its own if the manufacturer prescribes an internal spigot.
• Used standards: rust at the transition, cracks or a loose spigot rule them out. Loose spigots should be straight and slide in easily.

Used joint parts are listed under couplers.