Monday, June 15, 2015

Joint No 1: Sumitome hozo sashi

First joint of Project Mayhem.

I want to use in the corners of my future workshop and I guess Jason can use it too in the near future. 

You also need to put the numbers to the drawing depending in your pieces of wood. I would say that the size of the features is not critical but they all need to be there. 

Check the centre lines, they are useful (it seems).

We have 7 days to finish this. 

In case you didn't read the rules, go here:


  1. Yes! This is insanely complicated compared to the dovetail or bridal slip used in western timber frame sills. I didn't realize that the Japanese aesthetic of not showing end grain extended to house joinery too.

    It has begun.

  2. Pow! He takes one on the nose, ouch!

    Great choice, this will be fun! The obscured endgrain is more than aesthetic, it is practical for shielding the timber from exposure. Endgrain draws moisture, hastens decay. The joinery looks ridiculously elaborate, but details like this can mean the difference between a structure lasting for 100 years....or 800 years.

    At it's heart, most of this stuff is about practicality.

  3. A question....

    The tongue on one piece, that extends to cover the endgrain of the have shown it to have a taper, but other examples that I have seen make the tongue straight sided ( not tapered).

    Is there justification or a preference for one way or the other? The straight sided tongue would seem to be easier.

    Haha...easier! Yeah....

  4. No explanation whatsoever in the book. They just say that because of that, you need to make a stub tenon in the column.

    Maybe its more resistant that way, I always imagined the straight one to be easy to split there.

    Anyone has the lay out already?

    1. 7 am here...still drinking my coffee....and thinking.

      This is so fun, and a great idea as well. The challenge will be in the presentation. Looking at other examples of joinery, both this joint and others, brings to the forefront how little information there is on this subject.

      I don't remember where I was living at the time, but over 20 years ago I vividly remember looking through the 2 Japanese joinery books available at my public library. I thought, "Interesting, but far too complicated!", flipped briefly through, then dove back into my James Krenov obsession.

      What I wouldn't give, to have those books now, haha.

      What is lacking is information on the "why" things are done in a particular fashion. Things like joint proportion, cut sequences, do this, do it this way but NEVER that know? The joint has to be designed to accommodate the tools at hand (to a degree), so details and specifics of the design must be individually flexible, but there must be some standards. Japanese tools are not metric, they are Japanese imperial ( Sun, Bu, etc) so mortices are made the width of your chisel. Tongues and tenons would be convenient thicknesses for laying out, like the thickness of your square/sashigane, right?

      And is the centerline layout method the standard? So many questions!

      Thank God I brought my Japanese centering ruler!

    2. well, the tenon in the book is 30mm and seems like some squares are 15mm wide, so you put one square in each side. (I'm making myself a 7.5mm stick to mark that in my wood.)

      That's another reason I didn't put the sizes, if someone has a 15mm or 9mm mortice chisel, I would totally go for that instead of following rock written measurements.

      I hope tonight I can start working...

    3. This is the best that I have found, so far. The standard construction curriculum and instruction for trade schools. Big site, great pictures and information on the basics that we lack over here.

  5. When finished (he said confidently), where do we post pictures?

  6. If you want a taste as to the how and why of Japanese temple joinery I've really enjoyed reading "The Genius of Japanese Carpentry". Seven solid pages of cut sequence for a half-lapped goose necked scarf joint. At the scale the joint is used at to join ridge beams the guy only needed his sashigane to lay out both sides of the joint from a centerline.

    Only thing that's stumping me at the moment is why the cut line for the wedged haunched tenon is market at an angle?

    1. To clarify: the cut line for the wedge of the haunched tenon.

    2. No idea Gabe, the book doesn't say anything about it. I'm using wood joints in classical japanese architecture, btw.

      Did you read "just enough" by the same author? I found it 10 times better than the genius of japanese carpentry, which is really good too.