Monday, July 6, 2015

Project Mayhem Japanese joinery #3...I don't know what it is, but I know that I like it



Project Mayhem joinery practice.

  • One week
  • Hand tools
  • Take pictures
  • Write up your results (so that others can learn from our mistakes!)

Ladies and gentlemen....are your saws and chisels ready?



This week's project is one that caught my eye a while back, from a book that Sebastian lent me describing a series of traditional joints used in Japanese temple construction.



I picked out a subject for our joinery practice, but there is one minor detail missing.....the name!

If anyone out there wants to provide the name here, bonus points will be awarded! I have no clue myself.....story of my life,haha. Sort of a single sided, floating Shachi-tsugi I suppose.


This looks like a fun one, a great method of connecting a beam to a post that has already been erected and can't be moved. Like, need to add on to an existing structure. The floating tongue attaches to the post by means of a sliding dovetail, then engages the beam and is locked into place by a tapered wooden peg (a shachi-sen). The bulk of the beams weight rests on the protruding stub tenon, not the greatest load bearing capacity, but cool nonetheless.


One of the reasons that I wanted to start these joinery practice sessions in the first place, was to better learn more about the layout and cutting procedure best used for this type of elaborate joinery. That particular aspect of the craft is greatly lacking, so in the future I hope to do a better job of documenting the reasoning behind why I try to do things a particular way. Maybe that will help some of you other beginners out there.


As I do more of this, I am realizing that the most difficult part of the process might be to try something new in the first place, cut a joint that you've not tried before. Send pics and notes on your attempts, modifications that might make things work more smoothly, whatever.


It doesn't need to look perfect....Have fun!







On a related subject, Sebastian has started hosting a series of woodworking classes, so next time you are down south....



I was thinking that a couple of simple birds-mouth joints might make for some fun layout and sawing practice.



From Daiku-dojo

Two different versions, it might be fun to compare which is easier to cut, which one feels stronger, etc. Why these strange looking joints? Besides being good sawing practice, they are both examples of something that is simple to do using hand tools, but fairly difficult if you rely on powered tools. Lots of these seemingly complex things are actually fairly simple, once you have a little bit of knowhow.


All saw, no chopping, good practice!



  1. GREAT!

    Extra points for cutting the female part in a vertical position? As a matter of fact one of the project here is to make a roof over the entrance gate, whose pillars are 50cm under the earth, so I may have to use something like this eventually.

    Ok, enough talk, I go picking up my timber and saws. Sharpened last 2 days waiting for this moment.

    1. Triple extra-points if you use the joint to actually build something, haha!

  2. Excellent! This joint is totally new to me. These practice joints are really opening up my mind to what is possible.

  3. 2:20 with "only" two minor mistakes. The pin was not half the size of the mortice and I put the shachi-sen the other way around, so it opens the joint intead of close it :/

  4. Oh my gosh...
    This is going to take some time to wrap my mind around how to cut the mortise.

    I've always heard that the Japanese prefer simplicity, but I'm finding nothing simple in their joinery.

    1. As far as the complexity of the joinery goes....I'm totally with you. The more that I learn, the more that I appreciate the reasons why these things are done as they are.....and the more I want to just pull out the screws and call it done. I'm trying to build a quick and dirty workshop right now.....the temptation is great, let me tell you. I am studying this wonderful complex joinery, designed to last for 100's of years....I'm tying stuff together with baling wire, haha!

      I still tell myself that it is important to do work that makes me proud and conserves materials for future use, but right now I'm settling for the conservation of materials aspect. Baling wire is easily cut, and I can use the poles elsewhere. It kinda sucks though.

  5. Haha.......whoops! Send me pics! Your eagerness is humbling, I'm still planning dinner.....

    One thing that I was considering, the shachi-sen as shown in that illustration looks like it has a rectangular cross section, but many other examples that I have seen are trapezoidal. I was intending to try the trapezoidal myself as it seems like it might tend to draw the joint tighter.......what are your thoughts?

    1. Yeah, a slight tapper would help to bring the joint together. But then I don't get how to mark it. You need to put the key first in the final position to mark? or the wedged shape gives you some room to play? I need to make some diagrams it seems, I don't really understand that part yet.

    2. When you say trapezoidal do you mean the dovetailed key would be wider at the bottom than the top? Or do you mean a taper between the dovetailed bit and its far side away from the joint length wise? Since you are speaking of cross section I'm assuming the former, but then it does make cutting the wedge to lock it tricky.

    3. Sorry for not being very clear here. I have a hard time keeping this Japanese terminology straight, much less the English stuff......I meant parallelogram, not trapezoid, haha....oops.

      The shachi-sen is shown in the illustration as being rectangular in cross section, but often it is shaped to a addition to being tapered in its length. This would help it to draw the rod tenon tighter, in a more linear movement. If the shachi-sen is merely rectangular, there will be a slight spreading component, pushing the rod tenon and the adjacent cheek face apart. Jeez....could I say that more poorly?!

      Chris Hall has a great photo of a rod tenon, two shachi-sen, and the layout right here...

      The short face of the shachi-sen is 90* perpendicular to the length of the rod tenon itself. A'course then you need to give the shachi-sen it's taper.....I am assuming the it is the shachi-sen getting tapered, but not so much the trench that it fits into. I *think* that Chris might have explained the tapering part somewhere, but since this is one of those little questions that has been picking at my brain, it's possible that he was saving that part of the description, to explain later. I have always wondered if he shows it in his books?

      I hope that's correct, as I've got enough stuff to get backwards already, haha. It is interesting that while there are many books that describe joinery, show a multitude of pictures, there isn't anything substantial that shows the simple steps of this stuff. I am pretty sure that this is one of those little things that I am getting fixated on, more due to my inexperience than its real importance.

      I bet if I were to just cut ten of these things today, I would know about everything that there is to know. That would be more practical than me spending hours sifting for info on the Japanese websites.....quicker too, haha.

    4. Here is another post of Chris's that shows the layout. The trench is cut first.....then the rod tenon offered up...then the rod tenon gets marked for final layout.

      That way you know that things should draw up nice and tight.

      Another note...the rod tenon itself needs to have a gap at the end, between it and the mortice. Partly this is to assure that there is room to fully draw the joint tighter, but also.....

      ....There is the understanding here that hundreds of years in the future, this stuff needs to be disassembled to replace rotten pieces. The gap at the end of the tenon/mortice allows you to force the joint open again, using a wedge or crowbar. That is the stuff that really spins my dials! Crazy!

    5. Ha! One answer to a question of mine.

      Chris HallMay 25, 2013 at 5:59 PM

      thanks for the comment. If you're interested in learning further details about the intricacies of shachi sen, several pages are devoted to the topic in my Volume III of the TAJCD series. There are some important little counter-intuitive details which when observed make these joints come together as they should.


    6. And again.....

      Shachi-sen tapered in TWO DIRECTIONS. Let's figure this stuff out!

    7. The trench or mortice for the shachi-sen *IS* tapered slightly.


      Halfway down, Chris has a picture that shows him including a taper of 1-2 mm (a guess on my part) for the trench....from his post...

      Another view, this time showing the amount of taper inwards in the trench sidewall relative to the pencil line:

    8. that lay out picture is priceless. Will remake it soon copying that.

  6. would you happen to have any more pictures of it?

    Does the tenon go through the piece? I just can't think of a way that doesn't involve some crazy chisel shape to make a blind mortise to fit that dovetail.

    1. Hi Steven!

      I'm sorry, that's the only image that I've got, taken from a screenshot out of a book linked to me.....haha. I love how this knowledge is able to be passed down, albeit throught nontraditional means. The downside is that much of what we do still amounts to reinventing the wheel, sigh...

      The sliding dovetail, I was planning on cutting the shallow primary blind mortice using conventional means, then trying to cut the reverse angled sliding dovetail part using my azebiki-noko saw. Slight problem saw is surely too big, haha. This feels like one of those projects where the lack of one small thing derails me into making some ultra-specific task specific tool. If I do, I'll send you one too, haha.

      Sebastian has already finished....Maybe he has some hints?

    2. as Jason says, cut a shallow mortice first in the dovetail part. Then pare away what's not a dovetail. You could use a guide for it to have both the same angle or just go for it which is what i did. Then you put the key and transfer, with a pointy marking knife the angles. It's really just a tiny bit of material you need to remove.

      I do need to make something to clean the bottoms, this one was not as nice as I would like it.


Like all of us, I am figuring this out as I go, so when you see something that is incorrect or flat out wrong (and you will!), let me know. This is a learning process. Real people and names, please. Constructive comments and questions are very welcome, but hate speak/politics are not! Life (get one!) is too short.

Thanks, Jason