Kanawa-tsugi Joinery Models Part 2

Continuing along from last week’s post on making a batch of kanawa-tsugi joinery models….

With the joinery cutout complete, one of the remaining tasks for these joinery models was making wedges. The wedges are a bit tricky to make since they are tapered along their length and are also trapezoid shaped in cross section. The trapezoidal shape results from the fact that the sloping faces of the joint and the wedge shoulder cut aren’t 90 degrees to one another, which you can see in the close-up of the 3D model below.

Looking from the top of the 3D model you can just make out the slight taper to the wedge shoulder…

I considered a few different approaches for making the wedges, everything from router setups to simple jigs for handplaning the taper and proper edge angle, but ultimately I went with a jig on the sliding tablesaw.

Before cutting the wedges to length I first milled a thin board of oak to the finished wedge thickness in the planer. Then I adjusted the jointer so I could join one edge at the correct angle. From there I ripped and cut to length a batch of wedge blanks.

The table saw jig is pretty simple. Basically just a couple of stops and a toggle clamp.

The stop that supports the wedge along it’s length is angled to establish the taper of the wedge. Each blank went in the jig with the clean edge that came off the jointer butting up against this stop

I also tilted the saw blade to cut the appropriate angle (same angle that I used previously on the jointer), so when the wedge blank gets past through the saw it gets a slighty angled and tapered cut.

Here’s the wedge after running it through the saw.

and here’s a check of the wedge fit in one of the joints.

It’s impressive how tight these joints become with a few taps of the wedge, and it’s nice when the shoulder joints almost become inivisible. The gap you can see at the end of the stub tenon is intensional, and it’s similar to cutting a tenon slightly shorter than the depth of it’s mortise to prevent it from bottoming out, resulting in a gappy shoulder. The more solid the contact between the main shoulders of these joints the stronger they will be in use.

Here’s a look at another joint looking at the narrow end of the wedge. There’s a hairline gap on the sloping faces of this one, but the shoulder joints came out nice and tight. You can also just make out the trapezoidal shape of the wedge.

The next step for the joinery models was dying and finishing. (Prior to dying and finish I handplaned and chamfered each joint, but unfortunately forgot to take pictures.) One half of each joint was dyed with slightly thinned out sumi ink.

The next day I coated both halves of each joint in a Hassui Ceramic (liquid glass) wood finish. Finishing was super simple, just brush on a heavy coat of liquid glass, let it soak in, and dry. Initially the wood takes on a richer color but that mellows out as the alchohol solvent evaporates, and eventually the wood is left looking really natural.

And at last here’s the finished batch of joints, loosely assembled and more or less complete.

All in all, the joinery models came out pretty clean and tidy. The really tricky part was managing the fit between the two halves. I wanted to have clean tight seams, yet not so tight that the joints would be a challenge for customers to dissassemble/assemble. That balance was definitely the most challenging aspect of making these models. One issue that popped up in that regard had to do with finishing. Prior to dying all the joints were more or less dialed in how I wanted them, but apply the dye had the effect of ever so slightly raising the grain, causing some of the joints to tighten up. If I had to do it again I’d probably opt for an alcohol based dye to minimize grain raising, and/or make the initial fit of the joints just a touch looser in anticipation of the grain raising. In the end, a bit of wax applied to the interior face of the joint followed by repeated assembly/disassembly seemed to work well enough to “lubricate” the wood and restore the level of fit I had initially aimed for.

Up next I’ll share some photos from the next part of this project, which involved making four more joinery models, each different, in a slightly large size.

Thanks for reading.