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I am looking for a way to join 3 pieces of wood that would intersect each other.

This is the project I am working on :

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Example of joint :

Just like that

This is the japanese cidori joint system. Though, I don't like the system of cidori with the protruding members.

I had a very hard time finding a suitable joint on the internet.

So my question is :

1) Do you know of a simple joint that can achieve this (3 branch intersection), if so can you provide name and or plans?

2) I found images of a fairly complicated joint that could do it. The images are in too poor quality for me to analyze how it is made. Can anyone point what is the name of that joint, and if possible how to make it? (plans)

Thank you

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  • If you're seeking alternative joints for achieving the same result we could do with a lot of additional details. How much weight does the finished item need to support (just its own weight or is this for storage)? What size(s) do you want to build? What wood or woods will you want to build it from?
    – Graphus
    Commented Jan 29, 2017 at 19:16
  • The structure will hold a queen size bed that will serve both as bed and sofa for watching movies with friends so queen size bed + 3-4 adults. Total weight : 400kg. The size of the structure will be around 110 inches wide, 72 inch deep and 30 inches high. It has to resist lateral movement.
    – Ludovic C
    Commented Jan 29, 2017 at 19:26
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    You should pick a different structure. 400kg static load with an unknown amount of dynamic load?? This is the type of application that calls for joinery where you suspect you've over-engineering for strength, not where you worry the joints just might not be strong enough!
    – Graphus
    Commented Jan 29, 2017 at 19:34
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    The sheet material makes this a completely different ballgame. It becomes a structural component (particularly if glued in place and not just fixed with fasteners) and massively reduces the chance of racking, as well as taking a significant part of the static load. You can greatly simplify the framework elements (the internal ones that aren't needed visually) and not lose any strength here, saving wood and the time/effort needed for any joinery — no trad joinery is strictly needed, a lot of this could be done with pocket screws.
    – Graphus
    Commented Jan 29, 2017 at 19:53
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    I counted 245 +/- connection joints on this project and would estimate it would take at least 4- 6 hours each to make them. That works out to between 1000 and 1500 hours to make the frame. Good luck with that!
    – Ashlar ♦
    Commented Jan 30, 2017 at 1:04

3 Answers 3

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The standard three-way corner joint is the Kane Tsugi.

The five-way joint is the shachisen-tsugi-shikuchi-no-shihousashi. It is very complicated.

A much simpler option is the sampo-gumi-shikuchi, but the disadvantage is that beams do not meet all at the same point, but one is offset.

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2

Use long pieces that extend for the whole length/width of each side. In that case, on the sides, you only ever have two pieces intersecting (although it looks like three), and you can just use lap joints.

For the corners, use a lap joint for two of the pieces, then pierce them both with a mortise that accepts a tenon you cut into the third piece.

I'm certain there are much more complex approaches, but this is simple, clean, and will work.

Joint

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For #2, I can't name the joint, but might be able to unpack it enough for you.

Let's call the tall upright in the first picture the X axis. It has two mortises.

Y is like a pinned scarf joint. I suspect that it has one long tenon (that mates with a mortise on top of the other half) and one stub tenon that simply nests into X and provides stability (and resistance to rotation). If I was building this, I'd try to make the two halves symmetrical, but they clearly didn't.

Z looks like a relatively simple mortise/tenon that's been pinned for stability.

Unless you built this with fairly large stock, Z is quite weak. The rest have had so much material removed that they aren't great, either. (TL/DR: not for heavy use in earthquake country.)

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