Woven Kumiko Cabinet – Wedged Tenon Joinery

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I mentioned last week that my plan for the Woven Kumiko Cabinet was to make a cabinet that sits on the Toshi-nuki Shelves. I designed those shelves with modularity in mind, so the shelf boards themselves can easily be removed and exchanged for a cabinet, small set of drawers, etc. Here’s one of my earlier concept images.

A later revision of the shelf/cabinet design looked like this, featuring a woven kumiko cabinet.

The way I designed and built the Toshi-nuki Shelves to hold the shelf boards/cabinets was with a shallow rabbet cut into the top of each horizontal shelf support. The shelf boards simply set down into the rabbet which keeps them in place. Likewise they can be removed and a cabinet can be made to fit within the same space, again sitting right down into the rabbet which will keep the cabinet in position on the shelf.

All that is to say that the design for this cabinet involved taking into account that shallow rabbet space. I wanted the bottom of the cabinet to look like it was sitting right on the top of the horizontal support, so I designed the sides of the cabinet to extend past the bottom by 12mm (the depth of the rabbet). Doing so effectively raised the bottom panel to become flush with the shelf’s horiztontal support, while allowing the 12 mm extension on the sides to engage with the rabbet. Hang in there if this sounds a little fuzzy, I’ll try to share some detail pictues of the situation in a later post.

With the sides extending beyond the bottom panel my joinery options were somewhat limited, but it seemed like a good opportunity to use wedged tenon joints. Other options are certaily available, but I love the look and strength of wedged tenons. Up on the top side of the cabinet I decided to go with dovetails.

The wood for this cabinet is some really nice tight grain Japanese ash (tamo). I’ve had limited experience working with tamo but my impression so far is that it’s much lighter and a bit softer than the white ash I’m accustomed to from N. America. This material in particular was really light and easy to work. The grain was super tight and I managed to get nearly perfectly quartersawn material for the cabinet parts. I like to mill material to size as slowly as possible especially if it has been resawn from thicker stock. So after resawing and rough milling the material I let it sit for a few weeks as I worked on other projects, and during that time it barely moved at all. A testament to properly dried lumber if you ask me, and being quartersawn doesn’t hurt either.

So with the stock milled and cut to size I started laying out the joinery for the wedged tenons.

The layout you see here is on the sides of the cabinet.

In the close up below you can see the difference between the layout on the inside and outside of the joint. The panel on top is flipped over showing the inside of the joint and the panel on the bottom shows the outside. The inner most lines represent the actual mortise opening while the outer lines represent the adjoining panel’s thickness. The spacing of the inner lines is different from the inside to outside of the joint (inside=narrower, outside=wider) which when mortised and connected creates a tapered mortise to accommodate the wedged and flared tenons. Ultimately what you end up with are tenons that become dovetail like after wedging, and a mortise with a taper to match. Super solid joinery that also looks beautiful.

I have no association with the company, but I have to say I’ve really been enjoying using this Incra Precision Ruler lately. It’s been super accurate for laying joints like these.

So on to drilling and chopping mortises.

For the final paring of the mortises, I made a guide block with an angle that matched my layout for the tapered mortises and used it to guide my chisel for the final bit of slicing.

Here’s the outside of this set of mortises after paring.

With the mortises in the sides finished I moved on to the bottom and top panels of the cabinet which also use wedged tenons to join the middle divider.

With all the mortises cut I moved on to the tenons. Once I layed out the tenons on all the pieces I did a quick double check before cutting. Here I’m double checking the middle divider tenon layout and mortises in the top panel.

Next step was sawing the tenons.

I hand sawed the sides of each tenon but used the bandsaw to rough out the waste between. Quick-tip : lightly chop or score your shoulder lines before bandsawing to prevent the bottom side of the cut from tearing out. Here I chopped about 1 mm beyond my shoulder lines for safety sake.

And I used a paring block again for trimming down to the shoulder. This time a 90 degree paring block.

The tamo was really nice material to work with and cut easily with a sharp chisel.

At this point I lined up the tenons and mortises and took a look at the fit, trimming the sides of each tenon until things looked right. With this material being on the softer side I could trim the tenons so that they were slighty tight for a compression fit when installed.

Here’s a tenon that needed a tiny bit of trimming.

After trimming the tenon width, the next step was to cut the tenons to the final thickness, and here I’m double checking the dimension of the mortises on the inside face of the joint (the narrow side).

Then I used a router to run a test cut trimming down both sides of a tenon.

And double checked the measurement. A bit fat but close, so just a light adjustment to the router and then I could move ahead with cutting all the tenons.

Here’s how the tenons looked after routing the cheeks.

Followed by a bit of trimming to the shoulder line with a chisel.

And finally some test fitting.

Tight fit all around on the inside of the joint….

… And on the outside you can see the shadow lines on the sides of the tenons which will be filled once the tenons are wedged.

All that’s left for these joints now is to make some cuts in the tenons for the wedges, and assemble them. But before getting to that I needed to finish the rest of the joinery details like the dovetails and grooves for the door and back panel.

All in all things went well with these joints, but I did screw up the cutout of the bottom panel tenons. I had planned to have the top corners of the cabinet mitered, and I thought it would look nice to also have the bottom panel join with a miter, or in this case a sword-tip miter. But when I was cutting the tenons, I completely spaced out and sawed straight through my layout lines. Oh well. It forced me to forgo miters all around, but in a way I think that may be better overall. Aside from the kumiko panel the rest of the shelf where this cabinet will sit is composed of horizontal and vertical intersections, so in the end things will be a bit more harmonious I think.

See you next week for some dovetail work.