Woven Kumiko Cabinet – Completion

Hey there folks. I’ve been away the past few weeks visiting family in MN and spending some time back at Big Sand Lake, followed by a bit of work at a Japanese Garden in LA. Going back to MN was long overdue. It’s hard to believe but it was the first time I’ve been back during the summer since we moved to Japan 5 years ago. But it was great to be there. I didn’t realize how much I missed the smell of pine trees, barbecuing, swimming in the lake, and of course hanging out with family.

Now that I’m back in Tokyo it’s about time to finish up this series on the Woven Kumiko Cabinet. Previously I covered the wedged tenon and 蟻組 for the cabinet, and with those steps complete all that remains is the back slats, assembly, and final door details.

First up the back slats. The main cabinet is composed of quatersawn tamo (Japanese ash), and while I considered going with a complementary wood for the back slats, as I have done on other projects, this time I decided to stick with the tamo. The wood for the slats came from a different board of tamo with slightly coarser grain, making for a slight contrast between the back slats and main cabinet. But the overall color and tone of the wood is nice and unified between the back and main cabinet.

The slats are made up of 9 mm thick x 30 mm wide sticks of tongue and groove tamo. After milling the rough stock to size I moved on to cutting the grooves at the router table using a 3 mm slot cutter router bit.

Then I swapped out bits for a straight bit to cut the tongues.

Cutting this kind of joinery is pretty straightforward, and doing it at the router table makes it easy to make fine adjustments and dial in a good fit between the tongues and grooves.

With the joinery finished I handplaned the front and back of each piece while they were still full length sticks.

And from there cut them to length. With the slats roughly assembled you can start to get a sense for the look of the finished back, complete with a nice sheen on the wood after handplaning.

After checking how the slats fit together, I disassembled them and cut one final bit of joinery, a simple rabbet on both ends of each piece to allow the resulting tongue to fit in a groove previously cut in the cabinet.

Below you can see how the back slats look after sliding them into place. I used cutoffs of some 2 mm thick kumiko as spacers to separate the slats. My decision to use tongue and groove joints was to allow the slats to “float” and expand and contract during the seasons. So I factored in a space between each slat so that if the humidity rises the slats can expand ever so slightly, and likewise when the humidity drops they can shrink without fully separating from their neighbor. In otherwords, expansion should never cause the slats to fully swell and press on the sides of the cabinet (potentially blowing it apart) and should never shrink to the extent that gaps open between the slats. The big question then becomes, how do you keep the slats in position. One option would be to glue them just in the middle of each slat, effectively locking them in place while allowing for expansion/contraction. I’ve used that method in the past, but glue-ups are stressfull and with the interior of the cabinet and all the slats finish planed I also didn’t want to have to deal with potential squeeze out. So I opted to pin each slat in position with a little wood peg. It may sound finicky, but it actually worked out really well and was really pretty easy to do. But more on that later.

In preparation for gluing up the sides of the cabinet I double checked the spacing and width of the back slats, and added a bit of tape to prevent the spacers from falling out.

Then in was time for the big glue-up.

This glue-up actually went really easy, largely in part to the fact that I could skip gluing the wedged tenons since they don’t really require glue except for the wedges. With wedged tenons, tapping in the wedges will flare the tenon into a dovetail shape creating a really solid mechanical joint. So with no glue need for the tenons, I could put my focus on gluing the dovetails. I also put a bit of glue on the outer most back slats, gluing them to the sides of the cabinet. Below you can see how I clamped those outer back slats and the dovetails with some spring and pipe clamps.

Then I moved on to tapping in the wedges for the tenons on the middle divider. Here I did use a dab of glue on the wedges.

And here are the wedges installed in the tenons of the bottom panel.

With the cabinet glued up the last thing to fabricate was the door frame. The door frame is a bit unique, with a depth of 25mm to account for the layered woven kumiko panel. The thickness of the door rails and stiles are relatively thin at 12mm for the stiles and 15 for the rails. The rails will get a tongue cut on each to fit into a mating groove in the cabinet itself, and the plan is for a 12 mm reveal once the door is installed. When I designed the door, I wanted to keep the overall appearance of the frame thin and light, which on a traditonal door would make the corner joinery a bit tricky, but in this case with the extra depth I had plenty of wood to use some solid joinery. And ultimately I decided to used box joints to join the corners, since they should give a ton of strength, and it seemed like a straightforward option.

Unfortunately I forgot to take pictures of the joinery cutout, but it wasn’t terribly exciting anyways. I used a combination of table saw and chisels to cut the joints, and everything went pretty quick and smooth.

The bigger challenge was trimming the woven kumiko panel to fit within the frame. My strategy here was to dry assemble the frame and lay in on the panel itself to determine exactly where to cut the panel. That part was pretty straightforward but actually cutting the kumiko was a bit of a challege. I’ve experimented with trimming kumiko panels like this with machines like the sliding table saw, but it has never ended well. This is ultimately a task for a hand saw, which in my opinion, gives you the most control and has the least likelyhood of damaging the delicate kumiko.

You can see how I ended up cutting the woven kumiko panel below. I simply clamped a guide block and used a Nakaya 0.2 mm thick cross cut saw (sans handle) to carefully cut down through the layers. The guide block worked well to keep the cut nice and square. But the thickness of the guide block meant that I had to remove the saw’s handle since there is an attached spline the runs along the back of the blade which would have interfered with the guide block.

Here’s how the ends of the kumiko looked after cutting.

From there I reclamped the guide block and proceeded to trim the panel for the remaining three sides.

After trimming all sides of the panel I did a quick dry fit in the frame.

To glue up the door I skipped Titebond in favor of a standard PVA wood glue that is really common here in Japan. This glue dries clear making it a decent choice for areas where you might have a bit of glue squeeze out that may not be possible to clean up; like the tiny spaces around the ends of the kumiko on this panel. I figured it would be nearly impossible to clean up any squeeze without making even more of a mess. So my strategy was to lightly apply a layer of glue to the ends of all the kumiko pieces and very carefully clamp the door frame parts around the perimeter, trying my best not to slide or shift things which would end up smearing the glue.

Clamping was pretty straightforward and a bit of tape helped to pull a few stray pieces of kumiko into place.

With the door glued up, it was simply a matter of cutting a tongue on the top and bottom rails to fit within the groove in the cabinet.

Finally, for a finish I went with good old soap, which really keeps ash looking nice and light. I didn’t apply any soap finish to the kumiko panel itself, just the ash components.

And at long last here’s the finished cabinet.

One final addition after everything was assembled was the small feet on the sides and middle of the cabinet (with a matching set on the back side as well). I discovered that the cabinet sagged just a touch in the middle once everything was assembled so I added these feet to support the middle. The side feet weren’t necessary structurally, but design-wise I felt it made sense to add them to complement the middle. These feet really won’t ever be seen when the cabinet is set in it’s home on the Toshi-nuki Shelves, but they still function to support the cabinet.

And the door slides freely from one side to the other.

I’m pretty pleased with how clean the kumiko and door frame connections came out. This was the area that I had the most trepidation over, and I’m glad I managed to get a pretty clean cut with the Nakaya kumiko saw when trimming the panel to size.

Below you can see the left end of the cabinet with dovetail joints on the top corner and the wedged tenons towards the bottom.

It’s unlikely to be seen on a regular basis but I do like making a cabinet back that’s clean and nice to look at.

If you look close below you can see the little round pegs I used to pin the back slats. To install those I simply drilled a small hole (1.5 mm) in the center of each slat and used toothpicks for pegs to fix the slats in place.

And last but not least here’s the cabinet set in place on the shelves. I wish I could get a more expansive photo of the cabinet on the shelves but my current photography studio (aka my apartment) is too small to get a full view shot. But I like how everything turned out. The cabinet adds a nice break to the linear lines of the shelving, yet still looks unified.

Making the door for this cabinet is really what this challenge was all about. I started playing around with this pattern years ago but never took the leap to put it to use until now. Now that I have this experience under my belt I’d love to see how this style of kumiko wood look on some bigger pieces of furniture.

Well, that’s it for this build. Thanks for following along.