Monday, July 13, 2015

Yatoi hozo

According to "The Complete Japanese Joinery" the joint we are making is the Yahoi hozo, p. 203

Also in page 181 they discuss how to make the key slot and the key. They say that both the slot in the male and female part are "angled towards the center, or instead of tapering the slot, a tapered key may be used. "

The picture of the book is a not so clear, maybe the pencil line there in my joint should be parallel to the saw line... I vote for doing another joint with sashisen to understand this thing properly.

 And that's the top.

Then I made the wedge a bit tapered and got the angles by eye.

It feels real solid once the wedge is in.

but somehow out of square, seems like my dovetail mortice was not as square as it should. The inside corners were difficult to cut nicely.

Remaking the key and the wedge was like 1 more hour today, so let's say 3:30 in total.

So, when it's my turn again I would go for something like this:

But I guess it's Steve's turn, so surprise us boy!


  1. Can we derive any general principal in terms of wedge taper ratio or the fit of the wedge? I definitely like it best when both the wedge and the slot have tapered sides, getting as much wood in contact between the two as possible. I feel like it should be possible to lay out both the taper and parallelogram side angle on a piece of wedge stock and cut the thing with a saw, less tedious planing to fit.

    That four way joint! If I had looked at that before cutting this last joint it would have hurt my head. I look at it now and see a lot of variations on a common theme. It looks nice!

  2. Speaking as an amiture, I've made this joint, useing White Pine, which is relitively soft, like Sugi, and made it longer. 30 mm wide, 360 mm long. This allows the angle of the wedges to be less, and the width of the wedges is more, allowing me to make the wedges square with taper. Methinks the reason for wedges angled two ways is to resist wedge twist, which you would have with single angle taper. The potential problem with square wedges is forcing the pieces apart sideways and then twisting. The shorter the wedges the more the problem. For hardwood furniture you will likely make the whole thing shorter and smaller. Looking at the 3rd photo, it looks like you have room to have a wedge about twice as wide.

    Standard taper ratio is 1:12