I’m waiting for the finish to be ready on a couple of planes I’m working on, so I’ve been planning out a shoji exercise I’ve wanted to do for some time. I’m going to do a Ranma (transom) piece with a diamond or hexagonal structure and asa no ha (hemp leaf) details. You can see a fantastic example of the pattern in this screen by John Reed Fox, one of my favorite furniture makers. This is extremely detailed work, and requires a very high degree of precision to execute well. I’ve done a couple of basic shoji in the past, but this will be my first attempt at this complex pattern. There are a couple of critical handtool fixtures for this project that I wanted to show here.
Kumiko Thicknessing board and Kanna
One of the more critical parts of shoji work is making certain that you have extremely consistent thickness on all of the kumiko (the softwood lattice pieces in the interior). Any variations greater than a couple of thou are going to show up very clearly as a warp in the structure, or a very sloppy joint. So for the final thicknessing and finish planing of the kumiko, I’ve made a special plane known as a Hikouki Kanna
, as well as a board to run it on. Here is the kanna itself:
It’s basically a typical kanna, but with a pair of ‘runners’ on either side, planed to an extremely precise depth that defines the final thickness of your kumiko. For this project, I’m going to be using two different kumiko thicknesses, so I have two pairs of runners prepared – one for 3mm (~1/8″), and the other for 4.5mm (~3/16″). It’s a fairly straightforward concept, and is remarkably effective.
There is one ‘problem’ though, which shows up when trying to plane such thin material: the kumiko bend rather easily, and can be tricky to keep flat on the board when you approach final thickness. The solution is to build in a gentle ‘hold down’ device to get them flat to the board before reaching the mouth and blade. Here is the bottom of the kanna:
If you look just in front of the blade, you can see the mechanism – it’s a springloaded half-cylinder captured into the sole. The number and strength of springs can be adjusted to ensure the right amount of pressure.
The other part of this design is a dedicated ‘board’ that works very similarly to a sticking board. It consists of a lower ramp that the plane’s runners ride on, with a raised portion in the center. The kumiko are placed on the raised portion, which has screws at the end to serve as stops for the kumiko.
This ramp needs to be extremely flat, and I’ve used Quartersawn wood to help make sure it stays that way. In my setup, the central platform is raised 9mm (~3/8″), and my two sets of runners are 12mm and 13.5 mm thick – giving me kumiko of exactly the thicknesses I need.
Here’s the concept in action, which should make everything rather clear.
The Miter Jack
For the frame on the ranma, I’m going to use a mitered housed mortise and tenon joint that Toshio Odate describes in Making Shoji. It’s a tricky joint, and the miter itself is particularly critical for a clean fit – I’m using my miter jack.
I think shooting boards are in pretty widespread use by handtool woodworkers, but I’m not sure the miter jack is nearly as common — which I think is a shame. This is a fantastically powerful tool for any sort of joint that involves a miter. This is my second jack – I needed to remake it to work with my new Benchcrafted tail vise. There is a reprint from some fine plans for a jack at the most thoroughly informative website of Alice Frampton (ALF) in the UK: Cornish Workshop.
The miter jack can be used with a plane for a variety of mitered joints, much like the ‘donkey’s ear’ shooting board, which I think a fair number of folks are familiar with. Where the jack surpasses the donkey’s ear, however, is more complicated (and structurally sound) mitered joints – like this one, or the secret mitered dovetail. The two wedges of the jack are perfectly mated, and tuned to a dead-accurate 45-degree angle. The workpiece is clamped between these jaws, and the ramp surfaces act as a jig for the miter work. In this case, I’m using a paring chisel to define the miter:
The prepared rail, ready to be mortised:
I’m reasonably adept with a saw, but I’m not capable of getting anywhere near this sort of surface any other way. Here’s the joint, ready for assembly:
and the end result:
In short, it’s my opinion that the miter jack is a nearly indispensible tool for a handtool woodworker. There are other ways to accomplish the tasks it’s useful for, but none of them do the job as efficiently, or easily, as the jack does. if you don’t one, I highly recommend it as a shop project in the near future.
UPDATE – here’s a shot of the bottom of my miter jack, showing the modifications I’ve made to the traditional mounting block. Typically, these were made to work best in the opening of a traditional tail vise, where the jack can be pivoted up and down for access. This design wouldn’t work with the wagon vise style, which has no open clamping section.
For this one, I sized the mounting block to fit in the benchcrafted tailvise, and mounted it on a stationary platform that raises the jack off the benchtop about an inch. This was necessary to provide clearance for the screw handle, and it also allows me to mount the block in the center of the jack rather than the front or back rail.
The one sacrifice with this design is that it’s not really possible to pivot the jack front to back as you can with the ‘traditional’ tailvise design. To be honest, this is the one concern I had to switching to a wagon vise style – it’s about the only time I really used the open jaws on my old tail vise. For the most part, though, this will serve just fine, and in the cases where I really want to rotate the jack, I will mount it in my patternmaker’s vise, which gives it more positioning flexibility than any other system I can think of.