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I am looking into fabricating a steel tubing frame that needs to be dis/assembled (applies to many larger furniture like bed, shelving unit, wardrobe, cupboard, cabinet, ...).

What are the variants of the steel equivalent of a butt-joint and their pros/cons?

I have only found information on joints for construction steel (think skyscraper-sized double-T section) so far.

I have not found anything for closed sections in DIY sizes like 20/30/40 mm or 1 inch (easily available in hardware stores).

I am certain there must be something in literature. I might not be searching with the right terms.

Ideally, the connectors would be "invisible", i.e. hidden inside the tubing (square or rectangular).

I am considering welding a bolt to one part and a cap onto the other - one hole for the bolt, and another to enable tightening a nut inside the tubing:

enter image description here

Drawbacks: only one fastener, bolts may be too small, assembly of the nut very "fiddly". Pros: does not weaken tubing (depending on load/bending moment).

Another option:

enter image description here

Drawbacks: profile not tensioned, "snug" fit depends on availability and tolerances of tubing.

I'm also interested in connector-hardware made for this purpose.

handle
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  • Your first image could suit a 'cam lock' setup? – Jonathan R Swift Oct 28 '20 at 09:19
  • @JonathanRSwift As in woodworking? I've considered it, but it may need a tubular section to sit in (difficult to weld in), and I have doubts the tensioning works in steel (zinc cast parts?). – handle Oct 28 '20 at 09:41
  • Pins with taper locks - check those used on tailgates and some scaffolding systems. – Solar Mike Oct 28 '20 at 09:56
  • You can also get fun magnetic nut spinners to help with the fiddly aspect :) – Jonathan R Swift Oct 28 '20 at 12:19
  • What about dovetail with a pin? – NMech Oct 28 '20 at 19:24
  • Could you post examples? I was not able to find much on the suggested methods. The same question at https://diy.stackexchange.com/questions/155241/rectangular-steel-tube-bolted-connection. Lots of examples and solutions (products) at https://www.mcmaster.com/Metal-Structural-Framing-Tubing/ Also https://www.mcmaster.com/weld-nuts and https://weldtalk.hobartwelders.com/forum/weld-talk-topic-archive/welding-projects/15877-how-to-make-tubing-accept-a-bolt – handle Nov 17 '20 at 11:10

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See as an example the frequently used principle in the furniture industry. enter image description here

laurens van Lieshout
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  • Thanks, but see the comments to the question: https://engineering.stackexchange.com/questions/38417/detachable-tubing-connections-joints-for-frame-assembly/40104#comment68956_38417 – handle Feb 02 '21 at 11:34