Woven Kumiko Pattern

Back when Kay and I were in NY we went to an exhibition of bamboo work at the Met Museum, featuring woven bamboo baskets and artwork by Japanese masters of the craft. It was the first time I was exposed to Japanese bamboo work and it was mind blowing. The level of detail, skill and time that went into making the pieces on display was incredible to see. One piece that really caught my eye was the following flower pot by Chikubousai II.

On the whole the piece is beautiful but it’s the layered/woven pattern that really caught my eye. (For more bamboo work check out the Mingei Arts Gallery)

I was pretty taken by the design and went home wondering if there was a way I could do something similar using kumiko.

This is what I came up with. I made this little prototype panel back in 2017.

Unlike the bamboo piece above, there’s no actual weaving taking place, rather half-lap joints are cut on both sides of each piece of kumiko and offset creating a staggered pattern. (You can see the joinery on the little cutoff on the far left.) Overall I achieved a look that I was pleased with, but I struggled to figure out how to make use of the pattern. This patterns depth is what really sets it apart, but that also makes it a design challenge to use. The above panel finished at approx. 25-30 mm thick. While I’ve played around with different proportions forthe kumiko, I found that there’s really no good way to avoid ending up with a thick panel. Using half-lap joints to join the pieces requires a certain depth to the kumiko to maintain strength.

Fast forward to now, and that little prototype has been sitting in my shop for several years taunting me to make something. And I’ve been busy dreaming about different ways to put the pattern to use.

Here’s one concept that I drew in Blender last year. I like the idea of using the pattern on a wide surface like the doors of this media cabinet. One of the cool things with this kind of pattern is how it changes depending on your viewing angle and proximity. On a wider surface the whole thing becomes much more expansive and really draws you in.

Here’s a closeup of the pattern from the same cabinet.

I’ve also been playing around with some smaller scale designs like the cabinet below, designed to go on the Toshi-nuki Shelves I built a while back. After tweaking the proportions of the cabinet a bit, this is ultimately the piece I decided to make.

So let the woodworking begin!

After working out the proportions of the kumiko and half-lap joints I set about cutting up some kumiko strips. I used hinoki for the kumiko with the dimensions of each piece being 2mm thick x 4 mm deep. The panel isn’t that big but it requires a total of 8 layers of kumiko, so I needed around 104 sticks at 286mm long.

With the kumiko strips ready, then it was on to the matter of holding the kumiko in place for cutting. I ended up using a simple mdf fixture, very similar to the setup Des King describes in his books.

Here you can see the scale of the kumiko. And also make out a bit of snipe on some of the pieces where things start to look a little gappy towards the ends. This end of the kumiko is the waste side, and left long to avoid the inconsistencies in thickness.

For cutting the half-lap joints I wanted to try something new, using router and 2 mm spiral bit. I hoped that the spiral bit would give me clean cuts at the shoulder of the joints, while also providing a finished cut (both depth and width) in one shot. (I should also mention that I ran a test cut using the router bit in a piece of scrap and sized the kumiko strips to fit the resulting cut. That way you’re guaranteed to have a perfect fit with the half-lap joints.)

To guide the router I rigged up a simple sled. The rails on each side fit tight against the flat sides of my router so there’s no sloppy movement, ensuring a consistent cut width. I also attached a fence on the underside that keeps the jig square to the mdf fixture holding the kumiko.

The first piece of kumiko in the set has the reference marks for the pitch marked every 22mm. I’ve been using a Incra Precision Marking Rule lately and found it the perfect ruler for marking out the kumiko pitch. I get much more consistent results.

Here’s how things looked after cutting the first side.

My first cut was a failure. I didn’t have the pieces clamped tightly enough and they started to shift as I ran the router across. So after adjusting the holding fixture, I also had to readjust my reference kumiko and shift the whole pattern over to avoid the miscut portion. But once I made those adjustments the rest of the cuts went smoothly.

The first side’s depth of cut was only 1.5 mm, giving a total of 3 mm overlap between pieces when assembled.

After cutting one side of all the pieces, I removed the kumiko that will become the very front and back layers since those only need joints on one side, then flipped over the remaining strips and made another series of cuts. On this side the depth of cut is only 0.5 mm. This kind of super shallow cut would have been really tricky to do using traditional methods, but everything came out really consistent using the router.

My reasoning for the difference in depth of cut from one side to the other came about somewhat accidentally when I was playing around with this pattern in Blender. Initially I had been overlapping the kumiko evenly thoughout the pattern but at somepoint I shifted one half of the pattern creating an uneven set of half-laps, and the result looked pretty cool.

And then it was time for assembly. Here’s the first layer, already starting to look pretty cool.

Assembling the rest of the layers took a lot longer than I anticipated. I think in total I spent 2-3 hours just assembling the grid, and that’s without using glue. There wasn’t any need for adjustments other than cutting pieces to length near the corners, otherwise the joints all fit together pretty well. It simply took a long time to press all the joints together. Scaling this pattern up for a larger piece of furniture will definitely require some serious assembly time.

One of the things I really like about this kind of layered pattern is how it changes depending on the viewing angle.

I didn’t end up gluing the joints, partly because I wasn’t sure if I would need to disassemble things for some unforseen reason. But it turned out to be a really solid pattern even without glue. The joints were snug and with so many joints the whole thing holds together really well. That said I discovered later that not having glued joints made things tricky when I went to trim the edges with a saw. So next time I make one of these I’ll definitely use glue.

Thanks for reading. Next week we’ll continue on with the next phase of the project, so stick around.