Fittings
What is a joint pin?
A joint pin joins two scaffold tubes end to end from the inside, expanding within the bore of both tubes to grip. It is also called an expanding spigot.
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/joint-pin/diagram.svg" alt="joint pin — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
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<a href="https://scaffoldoptix.co.uk/glossary/joint-pin">What is a joint pin?</a> — diagram by
<a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
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</figure>Because it sits inside the tube, a joint pin leaves a clean external profile — useful where anything has to slide past the joint or sit against it.
It does not carry what an external sleeve coupler carries. Where an in-line joint has to take load, the sleeve is the fitting; where it is locating rather than carrying, the pin is adequate.
The tube ends have to be sound and round for a pin to grip properly, which is a real limitation on material that has been on site for years.
What goes wrong on site
- Used in place of a sleeve coupler at a joint that has to carry load.
- Fitted into damaged or out-of-round tube ends where it cannot grip.
- Not expanded fully, so the joint relies on friction that is not there.