This joint, man, what can I say. Every time I try one of these it is a challenge, seemingly just the right amount of challenge. What looks simple ends up being complex, the complex is simple. What do I want out of doing these exercises? Certainly I’m not going to run off to Japan and apprentice as a temple carpenter. These joints are often quite a bit more complex than what I use in my shoji work. Maybe one day I’ll build a timberframe, I know I’d love to, but that’s not it either.
Its something about the process. Its the same reason you might learn to play Go, the love of the challenge even when playing an opponent vastly more skilled. It doesn’t matter that you will probably lose, the proper attitude is almost more important than the skill.
Every once in a while, as today, I am cutting a joint and get that feeling of right attitude. I stand straighter, my hand holds the saw with strength and suppleness, and I am focused but not focused.
Brought to you this week by the inimitable Jason of My Peculiar Nature:
The layout looks so simple, does it not? I prepared the wedged key material as well as the dovetailed tenon before starting the cutting.
Lilly was asking a thousand questions a minute. Part of me really wants to focus, but how cool is it that a four year old wants an explanation about every single tool that I use and gets to see it in use? When I think about the different paradigm that she is growing up with, the access to unlimited information, it makes my head spin wondering what she will be capable of. First and foremost though is nurturing the natural curiosity that all children have before it is beaten out of them in one way or the other.
I used my brace and bit to lay waste to the mortise. I wasn’t really satisfied with using the bit because I always manage to over cut my line a little bit. Perhaps I should have just made the mortise slightly over sized.
See? The gods of joinery, as Sebastian would say, are frowning when they see a mortise cheek like that. I pared a bit too much off the left front corner of the mortise, and left too much on the right side. For a minute I thought I had botched the layout, and would have to start over to have my tenons properly align.
The mortise for the stub tenon was 1″ in width, the neck of the dovetail 3/4″. I cut the mortise to a depth 1/16″ More than both the stub tenon and dovetail, so I didn’t want to directly scribe the dovetail from the mortise cut to accept it. So, starting with the layout on the, what the hell do you call this part, removable tenon? I set my bevel gauge to the layout and used it to pare the 3/4″ mortise cheeks to the taper of the dovetail.
The keyed wedge! My god, what the hell was I thinking about all week when I presumed this joint would lay down before me and assemble itself. Apparently that thought did not extend in a constructive way to trigonometry, because I got to this stage and started scratching my head. I cut the material for the key at 1″ of width, square sides. I basically just started using my highly calibrated eyeball. Can you figure out how I did this? I feel like I need to cut another dozen of these keys (though fear not, there are more joints coming in the future that will use shachi-sen). I actually saw an excellent joint that Chris Hall used in a pentagram stool to lock mitered frame corners together: http://thecarpentryway.blogspot.com/2009/02/are-we-golden-iv.html
By a bit of marking I was able to determine the angles for the parallelogram sides. I added another wedge because its twice as much fun!
The layout for the tapering to the shachi-sen started on the dovetailed tenon, coming in 1/16″ from parallel on either side. The sachi-sen remained consistent in thickness, so I measured the depth inward on the bottom to match the top.
Once again the bevel gauge transfers the taper to the mortise walls. I realized that I sould have marked the top width of the wedge to be smaller than the width of my wedge material. I decided to compensate by paring inside of my lines a bit.
The parallelogram angles for the sides was planed in by eye, and then the ends were planed square to the length on a shooting board. I used the same set of my bevel gauge to mark the taper onto the wedge and planed it with a block plane. Only by sheer dumb luck did I manage to plane the taper on the right end of each wedge, the slant of the sides are opposites of each other.
Paring the slot for the shachi-sen in the beam was straight forward enough, checking the squareness of the non-tapered cheek with the bevel gauge set to square.
Assembly! The dovetail slots in with a few light taps of the genno.
Alas! I left the dovetailed-tenon too wide, it sticks up above the rail. It would be nice if my joints always went together correctly the first time, but then they are designed to come apart.
The second try at assembly went better. I had cut my wedges 1/8″ shorter than the depth of the mortise. I thought I would have a bit left sticking up to saw off but ended up driving them all of the way in. The shachi-sen does really pull this joint together! It created a bit of a gap between the post and the dovetail shoulders, but the joint is really solid. Beautiful really, I just wish I had a better grasp on cutting the sachi-sen.