Kawai Tsugite - Amazing Three-way Japanese Joint

This joint can be assembled three different ways - one in a straight line, two at right angles! It's a pretty weak joint, but boy is it a talking point. I hope to demystify it for those who would like to make one themselves, and believe me, it's a lot of fun to do, and great practice for sawing and paring.

Don't be daunted. Having worked out how to make it myself yesterday, I can give you all the instructions you need, and assure you that it isn't too hard to try. Getting a perfect fit in all three positions without it being sloppy is a challenge, and I could certainly improve on my effort in the future.

So, what will you need?

Materials:

• A length of square stock. Something like lime would be ideal as it is great to carve, but I used dark red meranti.

Tools:

• A back saw. Japanese or western is fine, and a thin kerf is best
• Chisel(s). Straight and skew chisels are a great help
• Marking gauge
• Try-square. A machinest's all metal square is best, but a carpenter's square is okay
• Mitre-square.
• Bevel gauge.
• Marking knife. A sharp pencil would be okay
• And preferably a workbench, vise, and bench hook

Step 1: Preparation

Plane the stock square all round

Both parts must be the same dimensions in width and thickness

I used a single piece, cutting it in half after squaring all round (this will allow a grain match when assembled in a straight line)

Shoot the ends square to the sides

Step 2: Marking Out (1)

Set the marking gauge to half the thickness

Mark a cross on both ends, and extend the ends of it down the four sides

Mark a band around the pieces, with the same gauge setting working from the ends

Reset the gauge to the full thickness

Mark a band around the pieces again

You should now have a cube marked on the end, each face of which is divided into four squares

Use a mitre square to define a full corner of the cube to remove (match the diagonals to ensure a grain match when assembled straight)

Step 3: Removing the Corner

Saw off the corner you just marked on each piece, and clean off the face to the marked lines

Step 4: Star Cuts

Set a bevel gauge to 22.5° and lay in the lines shown in the photo

These are the lines to saw to, and they extend around the back to meet the diagonal lines marked previously

Saw the three cuts that make up the star pattern

Step 5: Remove Waste

At the base of the 'removed' corner, you can saw a shoulder between the two star cuts

After that it's all chisel work

Carefully chisel away the bottom section from the star as shown, before removing the two other sections at the opposite corners (these are easier, as the saw cuts have done more of the work)

You need to continue until you form a base in these cavities that lies in the same plane, and which is parallel to the surface from where the original large corner was removed

Step 6: Assemble - Three Ways!

If you've removed sufficient waste, then the two pieces can now be joined together, in three different ways!

Don't expect perfection on your first attempt - mine certainly wasn't. Practice should make it better, and I'll be trying to fit some in soon.

Thanks for reading my instructable, and watching the video. There are plenty more joints and other stuff both on my Instructables page and Youtube channel.

Cheers,

Mitch

Comments

[NeilRG]

A practical answer to a kid asking about the real world applications and why they need to learn geometry.
I recall reading an article many years ago in Popular Science magazine showing complicated Japanese joinery being used in home construction to amazing effect.
This demo was in many ways a more demanding exercise because the underlying idea seems to suggest it's use in hardware free furniture construction, and so visual beauty is crucial.
In construction perhaps the grain matching and absolute visual perfection is secondary to time considerations, although Japanese artisans are known and respected for painstaking craftsmanship and attention to detail.
The article I read also mentioned that the joints would tighten up over time . Conventional nailed joints cannot make that claim.
Excellent instructable!

[giles2606]

This is a great instructable and a wonderful insight into high-end joinery - blurring the line between joinery and sculpture!

The only feedback I would give is to improve the lighting in your video - it's really good to see you working in the video but I kept trying to see precisely what you were doing and it was very dark.

The finished product is so good, it would be really worth trying to get better lighting as what you are doing is really well told :-)

Many thanks and keep going! :-)

[WOmadeOD]

Thanks, appreciate your comments

[oragamiunicorn]

this is a beautiful joint, and certainly a talking point. Does it serve any practical purpose?

[WOmadeOD]

Thanks. Personally I think it's main purpose is to show a craftsman's capability when talking to a client. But also to practice the skills used in other joints (it could get boring to just practice the same old thing time and time again).

[immort]

It serve's

1) practice

2) big square of contact when using glue to fix it = stronger connection (sorry my eng)

3) its beautiful )

[WOmadeOD]

Cheers. Replace "square" with "area", and "=" with "equals", and your English is excellent - much better than my ability with other languages :-)

[Man Up]

The Kwai Tsugite joint is not traditional joinery. It was invented by a mathematics professor in Japan more as a geometrical exercise based on traditional joinery methods. Traditional Japanese joinery itself is actually very practical at the same time as being ornate. Rigid joints like western style dovetail and mortise-and-tenon will fail in dynamic loading conditions experience during earthquakes. Japanese joinery is designed to allow some give under dynamic loading. But it should be used with specific kinds of woods. If you tried, for instance, to use North American Heart Pine, it would split the first time the joint was loaded.

Frankly, I've watched generations of woodworkers go mad in pursuit of the perfect hand-cut dove-tail joint. So anyone who does these kinds of joinery willingly are surely quite mad indeed :)