I just finished this Japanese transom yesterday and have been eagerly anticipating sharing this. When I first read through Odate’s book “Making Shoji” I marveled at the complexity of his kumiko joinery. While this certainly is a complicated project to execute, if you start with an understanding of the proper sequence of layout and are capable of accurately dimensioning your lumber the final assembly will go smoothly.
I bought some Hemlock a while back that I bought at a discount from the Woodcraft in Loveland, CO, because apparently no one wants to work Hemlock. But its a soft wood with even straight grain, from trees big enough to produce decent width vertical grain boards. I used Hemlock for the interior trim of my mothers house, and was pleased with how easily it worked. It does have a tendency towards brittleness.
I prepared all of my lumber in my usual manner, ripping on a table saw and dimensioning with hand planes. The kumiko I cut with a band saw from a carefully dimensioned 3/4″ board of vertical grain. The bandsaw kerf wastes a lot less wood than the table saw, an important consideration because kumiko must be cut from top quality lumber. The edge of the board is planed and squared after every cut, producing kumiko that only need to be planed to thickness on one side. To do that, I have a 50mm kanna from toolsfromjapan.com to which I have attached two pieces of kumiko the thickness of the final material I want but made from oak. I plane down one piece of kumiko to use as a cutting gauge for the mortises and lap joinery, and then shim out the thickness gauges with a couple pieces of paper and plane the rest of my kumiko. That way I have enough material left on the kumiko thickness to remove layout marks before final assembly, and can finish plane the kumiko to very controlled tolerances. Better than the 50mm kanna would be a plane with enough width to handle two pieces of kumiko at once.
I had to discard about half of the kumiko I cut because of terrible warping as they came off the bandsaw. Just because a board looks like it has straight grain doesn’t mean there aren’t other stresses in the board from drying. Perhaps its just the character of Hemlock. The frame componenets didn’t warp badly coming off the table saw so perhaps it was just that particular board.
In the above photo you can see the lap cuts after being cut and cleaned while attached to a kumiko cutting jig courtesy of Desmond King’s book “Shoji and Kumiko Design” . I was struggling with making these cuts while holding them atop saw horses as Odate demonstrates.
With the lap cuts done I mortised the tsukeko, and cut the blind mortises on the horizontals.
Great care must be taken when cutting these blind mortises. I was working atop my planing beam, which is doug fir, and found that even though I didn’t cut all the way through, the pressure from cutting dented out the other side of the mortise. Next time I try this I’ll be sure to work atop hardwood.
Assembly of the kumiko was surprisingly easy considering the number of pieces. The lap cuts alternate on the verticals but are cut all on one side for the horizontals. No need for glue here, the tsukeko frame holds things together nicely and will tighten up when the main frame is assembled around it.
From there I moved on to what seemed quite daunting at the time, the asanoha pattern pieces. The entire pattern is made from only three internal pieces within each square. They are: the diagonal, the hinge, and the key. Above you can see me fitting the hinge piece against the diagonal.
Here is my setup for cutting all of these little pieces. In the foreground I have my angle shooting jig with 45 and 30 degree angles. I’m using a WoodRiver low angle block plane. To the right of that is my miter box. Both employ cutting stops that trim each piece just slightly over size. From there I can individually fit the pieces to their opening. It was much faster to take a whole set of pieces through every operation at once than to cut and fit pieces one at a time.
With the diagonals in place you get to the most challenging part, the hinge. You have to cut exactly in the center of the piece, only leaving a tiny bit of wood the thickness of a sheet or two of paper.
To make a cut like that consistently is a matter of thousandths of an inch. Once again, Desmond King comes through with a great technique utilizing a lamp shining horizontally against the saw. I just have to say thank you to King for a simple and elegant solution that I never would have learned short of studying in Japan. The low angle of the light exaggerates the thickness of the remaining material by a factor of at least 10x. It also allows you a visual reference for holding the saw exactly horizontal in the cut. You want to use your thinnest kerf saw for this. I use a Nakaya Eaks 210mm kumiko saw from toolsfromjapan.com.
Once you’re working on the key its just a matter of spending the time to make all of these little pieces. One thing that Odate does not mention is trimming down the 60 degree nose at 90 degrees a pass or two thicker than the kerf of the saw that you used to cut the hinge pieces. If you don’t, as I found out, the sharp angle will cut through the hinge when you try to insert it. I’d rather have a tiny gap at the tip than a gap at the sides.
After the first leaf on the left was done and I settled into my technique my fits improved considerably and I went back and junked a couple of pieces with bad fits. My fingers ached from holding the block plane and the sharp little pieces in the angle jig, but I got it done.
Stay tuned for part two where I mortice the frame and cut the totally awesome mitered boxed mortise and tenon joint!