Category Archives: Joinery Etude

Joint No. 3

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.

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Brought to you this week by the inimitable Jason of My Peculiar Nature:

http://mypeculiarnature.blogspot.com/2015/07/project-mayhem-japanese-joinery-3i-don.html

The layout looks so simple, does it not? I prepared the wedged key material as well as the dovetailed tenon before starting the cutting.

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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.

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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.

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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.

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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.

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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

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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!

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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.

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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.

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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.

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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.

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Assembly! The dovetail slots in with a few light taps of the genno.

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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.

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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.

Cutting Koshikake Kamatsugi (Stepped Goose Neck Splice)

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I thought after last week that somehow this joint would be easy. Its certainly straight forward in cutting, but there were some new challenges that made executing this joint much more than a walk in the park. Time from layout to a joint that actually fit properly, 4hrs.  Can you see that I added a taper to the back shoulder of the goose neck? I thought it would make things easier and pull the whole assembly tighter.

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Here, the layout for the female side of the joint. Both sides of the joint were marked out before beginning, no transferring of marks. All of the marking was done with a fine tipped marker (.3mm) and sashigane.

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The layout for the male side of the joint. I started my cutting with removing the bottom half of the lap.

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Once again, I did all of my cutting with the piece horizontal on the bench. For this joint I tried cutting horizontally, which I’ve never done before. Definitely felt a little strange, but I had already cut both sides of the line down to the shoulder with the saw vertically, so the saw was just finishing the cut. I should have stopped right here and sharpened the rip side of my ryoba, I knew it was feeling a little dull and floating around in the cut, but…but what, I don’t know. Sharpen your tools when they get dull and sawing is a pleasure of a challenge, not an exercise in frustration.

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With the waste removed and pared flat I finished the layout on the bottom. With the timber in the same orientation I cut down one side of the cheek of the goose head, flipped the timber over and finished the cuts all the way to the haunch shoulder line. Then I made the cross cuts into the neck.

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A chisel pared the waste along the neck line.

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As you can see, a bit more wood has to be mortised out to define the horizontal and vertical haunches. I also chamfered a lot of the outside corners on the bottom of the goose neck.  It  was right about at two hours in when I finished this side. I thought The other side would be faster, but mortising with a chisel always takes me longer than I think it will.

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For the female side, removing the step that houses the horizontal haunch of the male side, and finishing the layout.

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I used a saw to cut for the vertical haunch , as well as cut as deeply as possible into the goose neck before chopping the waste with a 3/4″ chisel.

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These interior surfaces are what make this joint so challenging. There are so many of them that need to be perfectly vertical, or the joint will never go all of the way together. I used a small bevel gage set to square to check. All of this paring and checking, it really slowed me down. I also used this bevel gauge as a depth gauge when paring the bottom of the mortise. It was nice being able to run my chisel, bevel down, to clean the waste from the bottom.

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I grabbed the taper angle from the side of the layout with my bevel gauge and marked the interior of the mortise wall. I thought about just eyeballing this for the cut using the markings on the side of the beam, but that would have been a mistake. Getting this taper correct was the key to having this joint fit properly.

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The finished joint. Well, I forgot one thing, chamfering the outside edge where the bottom of the goose neck meets the vertical haunch. That was mistake number one that kept the joint from going together all of the way.

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For the longest time the tip of the goose neck fit flush, but the step was still 1/16″ high. I took it apart, checked my surfaces for square and flat, pared a little here and there. I must have taken it apart a half dozen times and each time could not figure out what was preventing the step from sitting all the way down. Finally I realized that the taper at the back of the goose neck was too acute on the female side of the joint. It was keeping the back of the goose neck from seating all of the way, and I thought it was a problem at the step. I was wacking it with a heavy hammer, thinking, surely it can squeeze in there a bit more. Nope, it needs to be almost perfect. The joint fit properly after paring. The taper became snug the last 1/16″-1/32″ before the two joints were flush. With a good fit the two pieces of the splice lay in the same horizontal plane, flat on the bench. I did manage to introduce a little error in my marking, you can see a small gap where the shoulders meet over the step. I need to get faster! Way too slow, and I was trying to move with a purpose.

I’m ready for more, what do you think for next weeks joint?

Wedged Mortise and Tenon

I realized that I’m getting ahead of myself with some of this beautiful Japanese joinery I’ve been practicing. I skipped over the wedging of the tenon for Joint No. 1 and really missed out on picking up some important details. Namely, paring a taper on the outside of the mortise such that the wedge truly locks the tenon in the mortise. Having planned to use this wedged tenon in my shoji garden gates I’m currently working on, I figured a practice try was in order.

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This is a shoji stile, 1-1/8″x1-3/16″, with the back taper on the mortise 1/8″ wider at either end than the tenon. This puts the wedge taper at a 1:5 ratio, quite obtuse by most measures. I figured if I could get away with this heavy of a wedge, I could comfortably relax the taper ratio for my garden gates and not worry about splitting the tenons when driving the wedges. My reference for the proportions was Jay Van Arsdale’s book on shoji making.  He describes how the back taper extends about half way down the depth of the mortise, and the cuts in the tenon for the wedge are made at a diagonal. This was news to me, even having read this book…

I thought tenon wedging was done with a wide kerf saw to make the cut for the wedge in the tenon, no back taper, and wedges with very little taper. It hurts to be wrong, but the time to learn is now before I produce a joint that lacks strength and longevity.

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I’m used to tapering in the sides of my blind mortises so that the tenon is compressed as it is driven together with the mortise. Toshio Odate, in his book “Making Shoji”, describes the shape of tategu through mortise as an hour glass, pinching the tenon in the middle. He mentions nothing about flaring the outside of the mortise wider than the tenon, but perhaps there is a middle road. This picture isn’t representative of the taper I pared in the end grain. In general, I’m trying to taper the mortise in so that the middle is about 1mm narrower for softwoods. I figure compressing the tenon at the point that it most wants to split when the wedges are driven will go a long way to keeping the joint together. If I was to cut the end grain to a barrel shape the tenon would have room to split.

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Can you see the saw kerf for the wedges in the tenon? They were cut with a very fine saw starting towards the outside edge of the tenon and leaning inward. I’ve always seen these cuts made straight down the tenon, but I imagine this diagonal cut lowers the chance of a split running out from the tenon, as well as allowing more flexibility at the tip of the tenon where it needs to move over the  most. I should have made the wedges about a centimeter longer than needed and cut off a bit of the sharp point on the wedge, but this still worked out.

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Look at how much room there is! This is the sweating moment, when you wonder if wood really is this flexible of a material (and I’m a bowyer).

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Success! One of the wedges needed to be driven a little deeper than the other necessitating the use of a nail set to drive it down, but it doesn’t show much after planing. I feel like the back taper on the mortise was more than needed, but it comforts me to see just how much the wood will move over without splitting. The compression at the middle of the mortise was definitely a good idea.

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And now in practice, using a small sliding bevel to gauge the back taper of the mortises for my garden gates. I used 1/8″ more width either side for these mortises as well, but the stiles are 2-1/2″ wide, making a taper ratio 1:10, half of the previous example. Screw the glue, wood is good.

Joint No. 2: Koshikake Kamatsugi (Stepped Gooseneck Splice)

Were back at it again! This is joint no. 2 for our series Project Mayhem. As always, if you’re reading this feel free to join in and we can learn together. The rules are here, but to recap a la Sebastian:

No electric tools.

Document the process.

Document the tools used.

Time it.

Discuss it.

Blog it.

I knew I wanted to do a scarf joint, I just didn’t realize how awesomely complicated they can get in execution. I thought the gooseneck splice was complicated, but its unfortunately one of the simpler ones, and builds on the layout and execution skills developed in the previous exercise. So here we go…

Diagram

I have tried to provide some simple ratios to help proportion the joint.

Gooseneck

This is a great joint for connecting groundsill beams together when you’re building your dreamy timber frame shop.

Gentlemen, there are seven days from today.

Finish by June 30, 2015

Bonzai!