Category Archives: Joinery Etude

Isuka Tsugi


A little warm up joinery? Looks simple enough. This is a simple form of isuka tsugi, or halved rabbeted oblique scarf splice. I’m hosting a Japanese carpentry study group meetup this Saturday to study these joints, so I wanted to get in a bit of practice such that I’ll be useful explaining what I’ve learned.

This joint is mainly used on cosmetic applications, like the interior ceiling rafters on a drop ceiling in traditional Japanese construction. Its also used as a ware-away on the top of batter posts when laying out a foundation, not a friendly surface to sit on and throw off the layout, haha.

I’ve never seen a western carpenter cut spikes on the top of a foundation layout posts for stretching string lines, I wonder why. OSHA may have a fit! When I recently layed out the foundation post holes for the greenhouse I built I actually ran in to the problem of people wanting to sit or lean on my batter posts.  Hell, I wanted to sit on them, or grab the top to stand myself from a seated position. Good idea, and good practice for apprentices new to the saw.


What you notice right away is that the central rip shares a cut line on the end face. At first I assumed that I’m missing something important in cutting this joint. But consider, if you first cut half way down the end grain face for either side, most of the joint is well defined on its face grain cheek surfaces. I tried my best to ride the edge of the adjacent kerf without slipping into it, but its all but impossible. The saw slips into the kerf and undercuts the cheek surface a bit.


Surfaces from the saw, marking with sumisashi and ink on 1-1/2″ square stock, using 210mm ryoba saw.


For such small cross section material it made more sense to use a marking knife and kebiki for the joint layout. I also used my dozuki saw and a piece of kumiko as a cutting guide. I’m slow with my sashigane, I know that from watching better carpenters than I at work via Youtube. It took me longer to lay out the joint than to cut it.


On to a more complicated variation. Here’s what it looks like when you draw it incorrectly, haha.  While in the midst of this useless layout a small bird flew into my shop and slammed into some window glass trying to chase a fly. The poor little fellow was so dazed I was able to pick him up and find a tree nook for him to recuperate. It wasn’t a great moment, the bird might have had a broken neck. Thankfully a little fresh air and he took back to the skies. And I was able to draw the joint correctly, well sort of.


I scaled up the lumber a bit to 2″ square. This variation has a cool parallelogram key to lock the joint, sachi-sen. I didn’t get the ratio of length to cross section correct, and I’m actually missing a bunch of cut lines, but I started cutting to find out. Made a bunch of cuts actually, all over the place.


With not much wood removed as a result.


Most of the material removal came down to being chopped away with a 1″ bench chisel. This blue stain pine is very soft, the chisel work was fast.


The mating joint is identical in all respects. I wised up a bit and added more cut lines. I shouldn’t have taken out the waste portion of the ‘v’ in this photo, it removed my cut lines for the central rip before I had a chance to saw to the line! Still not much of a problem though.


Looks like the subject of an Escher print.


The assembled joint, planed out and keyed with a tapered oak wedge. The joint showed a tendency for the two halves to assemble with twist if there was any proud surfaces. Getting the joint to come together in plane seems to be the major challenge of doing an acceptable job.

Feeling warmed up? Time for hip roof joinery.

What happens when woodworkers meet?


The first meeting of the little Japanese Daiku study group I formed was great! I’m late to writing of it because of the greenhouse, almost finished, so close.  That and every once in a while its healthy to take a break from the computer and let your vision drift to the far away.


Thanks to Peter and Eric who were in attendance we had a lot to discuss, starting with Peter’s excellent set of sharpening stones. Unfortunately I can’t remember the names, perhaps naniwa for the colored ones? They were softer than my Shapton ceramic/glass, and very fast. With the addition of a nagura stone the slurry gave a beautiful polish for the grit range.

This is a great example of how woodworkers immediately benefit from getting together. No woodworker can afford to buy a bunch of same grit stones to compare, so naturally the sharpening stones are the first thing of interest when woodworkers meet, regardless of place or time.


Eric brought an excellent set of honing films, which cut more slowly than the water stones/ but left a very bright clean polish. If you’re looking at what to get for sharpening, something between the cheapness of sandpaper and the healthy expense of a set of natural stones, it is honing film. Works great, seems to be holding up okay for Eric, and is available in a nice range of grits and very moderate costs.


The beauty of the day? A large natural stone, comparable to 1000/3000 grit range. Didn’t work on it too much because it didn’t have enough soak time when we first started. It felt very coarse in use, but the polish had character, very nice stone!


Somehow aviator sunglasses and sharpening stones look cool together, notice the concentrated but relaxed look on Peter’s face, perfect attitude for sharpening.


As part of re-organizing the shop to make room for more people I put together this bench set-up. I locked my trestles together with a diagonal brace on either side, the beams are 4×6 screwed to the trestle  with a couple smaller boards thrown across the middle to put tools on. Pretty solid in use too. The 4x6x8′ are about $16 dollars a piece, something like that, so this is a very affordable setup, and easy to keep the beams flat. I was a little worried that having two people pounding on it at the same time may make it difficult to work, but it really wasn’t a problem. Haha, Sebastian advised me not to make it too nice, hopefully this is okay.


Peter had to take off after the sharpening stone shoot-out to prepare curriculum for the start of classes at CSU. The city of Fort Collins is repopulated with young eager minds, ready to throw a party.

Anyway…Eric and I got started with the layout for stepped dovetail splice.


This is the first time that I used a level in combination with my center lining. In this case I really only cared about the flatness of the top face, and after leveling that top face, dropped a vertical line across the end grain with a level. The implication is that perpendicular marks across the top for the joinery layout are marked out square from the center line, not the edge of the timber. I’m still learning the potential of this center rule method, its a very powerful technique.


Eric got right to work after layout, showing a natural speed that had me concentrating to keep up. So cool to work together, always watching out the corner of your eye for some new technique, like the apprentices of old.


This is a good example, body position relative to the chisel locked together by connecting the hand with the chin, paring an end grain surface.


The joinery came out well for me, and we learned a lot finding the hiding surface that was proud in Eric’s joint while drinking some refreshing iced white tea.  Even though the timber was uneven, the center lines came together nicely.

The next meetup has been scheduled, I look forward to it greatly. It is these personal connections that lead to real growth in our craft.

Cutting wedged mortise and tenon/ box joinery.

Saturday, Sep 5, 2015, 12:00 PM

Location details are available to members only.

2 Members Attending

The first meetup of the Japanese Daiku study group was a blast! Let’s continue on with the exploration of classical Japanese timber joints, to cut the wedged mortise and tenon. All of the basics of good joinery are included, accurate preparation of the lumber, center line layout technique, use of the saw and chisel.What tools should you bring? Goo…

Check out this Meetup →


Cutting Okkake Daisen Tsugi (Rabbeted Oblique Scarf Splice)


Peter, who stopped by last weekend, was kind enough to let me photograph a set of old Japanese chisels he had picked up on etsy. This set is quite characteristic of some of the great deals to be had. I forgot to ask what the cost was, but it was probably close to the cost if you bought new only the 48mm chisel on the left.

I really love to see the worn down chisels. You look at that and think, don’t you want to have a bit more registration surface on the back of your chisel when paring? I suppose by the time you ware that much steel off in sharpening, you don’t need the large flat, you can just pare flat.


I made the layout for this joint to show my guest Peter, it not being strictly part of project mayhem. It sat there looking at me in such a compelling fashion that I had to go ahead and give it a try. My first oblique splice, among the many variations of this joint that exist!


Because both halves of the joint are very similar they are divided into the upper wood and the lower wood. I’m finally starting to realize how the sashigane speeds up layout. I’ve been using 1/2″ as a sort of nominal gauge for a lot of the haunching and, in this case, rabbeting marks. The sashigane being 15mm wide, it is used for the same purpose, but directly, so no measurement is required, you simple use the tongue of the square as the reference.  I recently ordered “The Complete Japanese Joinery” and am hopeful that it can give more insight into these time and accuracy saving uses of the sashigane.


Before I begin describing the cut sequence, a note. Cutting a joint like this where the two haves are almost the same is great practice! What I quite obviously did wrong for the first half was corrected, and the second half actually gave me the chance to apply my new found knowledge.

I started the first half with the rip into the main cheeks of the scarf. I started the cut with the saw vertical, and then rotated the timber so that I could saw along in horizontal fashion. Its definitely a new skill to turn the saw on its side. I seem to let the top of the plate rest on the bottom of the kerf, producing a cut that slants upward away from the line. Its difficult without more experience to get a feel for the saw in the cut. If you stand up too much you’re bending the saw and things go awry, kind of like swinging a golf club.


I stopped the rip cut when I realized I hadn’t thought through where I was going, and cut the shoulder line so that the rip had somewhere to meet up with.


Paring such a large flat surface was difficult! Too much time spent carefully checking with a straight edge, and very easy to gouge in and remove too much material. The surface quality of my cheek suffered as a result.


I marked the taper that draws the two halves of the joint together in assembly and made a series of waste cuts to the line for the lower cheek, which were then chopped with a chisel.


Don’t you just hate it when you’re paring across the grain on a cheek and blow off part of the line? The line is all you have.


In any case, the cheeks were pared flush and the layout finished for the through pegs that lock the joint. Evidently the square peg gives you the option of using a double wedge to lock the joint and tighten incrementally.


The housing for the rabbeted tongue on the tip of the scarf was chopped last, after sawing to the line on both sides.


For the second half of the joint I wised up, starting the cut with the rabbeted nose so that I had full support while paring the surfaces. For the cheeks I started with the shoulder cut and repeated my horizontal rip to the shoulder, and then immediately made the series of waste cross-cuts that allow the waste to be chiseled out for the lower cheek. Now there is room to plane the top cheek surface with a kanna, incomparably easier than paring. At the size of these joints you’re basically paring the face of a small board, the kanna makes sense.


I took the fence off of my skewed rabbet plane to pare the lower cheek. I’ve never used this plane to pare such a large surface, it was awesome and fast.


The first fitting of the joint was really disappointing. I know from previous experience that I could pound on this joint all day long with a sledge hammer and it would never come together. Bring the hammer out for the last 1/16″ or so of fit and not before, its better than waiting for rainbow farting unicorns to descend and push the joint together.

I spent a bit of time looking at the joint, trying to figure out what surface was proud. It must have been a small error in measurement, my sashigane technique. That is, marking one side of the scarf slightly longer than the other. I had to pare down the rabbeted nose on the left in the photo, as well as the shoulder that forms it, by almost 1/16″ before the two halves met nicely. I just don’t imagine having the luxury of repeatedly trial fitting a joint like this if the scarf was connecting two large, long, and heavy ass beams.


I already had some cherry scrap planed to 1/2″ square, so that’s what was used for the draw pin. Because of how the joint slides together, I would think that trying to use the draw pins to force in the last little bit of fit could lead to splitting along the cheeks of the mortise walls.

The first meetup for the new local Japanese carpentry group will be next weekend. I’ve been surprised at the level of interest in such a short period of time, it will be an awesome experience to work together for the first time, figure out what can be accomplished when we learn together, even if just to drink a beer and joke about our mistakes. I had in mind that this joint, or a variation thereof, would be the work of the day and I encourage anyone to step up to the challenge. If you don’t have a little bit of an ‘oh shit’ moment when you first look at the joint, then you probably need to practice something more complicated.

Study Japanese Carpentry in Northern Colorado


Interested in working with and learning from other hand tool woodworkers in Northern Colorado? So am I, and I’m tired of slowly bumping into people locally as luck will permit.  This is the modern age, the internet has made everything closer, and knowledge is just a click away. But it still remains that humans learn best from watching the successes and failures of other humans, not from staring at flickering images on a screen.

So lets get together and learn!


I propose we meet in voluntary association, bi-monthly on the first and third Saturdays, at a mutually agreeable location central to Fort Collins, CO, to plane together, chisel together, saw together, and learn again what quality construction means, through the study of classical Japanese timber joinery.

At each meeting a new joint will be chosen, to be practiced and studied during the week and cut during the get-together, probably for a couple of hours in the afternoon. Hand tools of the human powered variety only for cutting the joints, and you supply your own practice lumber. Common construction 4×4 will usually do.

Depending upon the number of participants and the skill level, instruction will annually culminate in a design project and structure build from locally sourced timber, to practice what has been learned.


What is happening in Colorado? I see grid after grid of new housing development slowly bulldozing its way across the front range. And what do you get for $500,000? The same quality of construction for a mobile home, merely a larger box with more expensive veneers.

The tools you will need (or their western equivalents):


A couple of hammers, a couple of hand planes, some chisels, 240mm ryoba saw and dozuki saw, some sharpening stones, brace and various bits, layout tools including carpenters square (sashigane), bevel gauge, marking gauge, marking pen and knife, try square, and optionally, ink line.

Additionally, a planing board (pictured), cushion, and saw horses, or a planing beam, perhaps a few clamps.

IMAG0978 This is me, Gabe, who you will be learning with.

This is the text:

Blogs for study:

Chris Hall’s “The Carpentry Way”

Mathieu’s “Fabula Lignarius”

The idea for a local group developed as the direct result of the efforts of Sebastian Gonzalez’s Project Mayhem 2.0

Additionally there is a timber-framing school in the mountains west of Fort Collins, though I have yet to attend: Rocky Mountain Workshops

Interested? Of course you are! Its free, although people will probably appreciate you more if you bring some cold beer.

Interested, but don’t have any skill? You’ll still need the tools, but I’ll be happy to instruct in the basics of dimensioning stock with hand planes, sharpening, marking, and posture of the saw, which can be worked on in lieu of cutting a beautiful and complicated joint.

Don’t wait another week, contact me through the comments section below or my email,

Joint No. 5 Double Plug


The lumber for this weeks joint from Project Mayhem 2.0 started as a small tortured little log. Not only is there a ton of twist, but bow as well. Half of the fun for this joint will be watching what it does as it dries. I don’t have anything to seal end grain at the moment so it’ll be a fast and hard drying for beam pieces after they are cut to length.

This was also the first real opportunity I’ve had to run my smaller maebiki-oga. I can tell it still needs a fair bit of work to get it cutting properly. Not enough set, my only saving grace was the small size of the log that kept the cut from going too crazy.


Planing green lumber though, man that is nice. Heavy shavings came off with ease and I had my stock squared up in no time. Finally a photo so that you get to see more than my hands and feet!


Here is the layout for the rod tenon side of the rail connection. Lots of wood to remove! You’ll feel like a real sawyer by the end of it.


And the other side has a receiving mortise for the rod tenon that goes through the post, as well as a small stub tenon at the bottom. The cogging/haunch either side of the tenon is a new twist, and I can see how it would be a good thing to increase the surface area that resists downward forces as well as guard against twisting.


The post mortising layout is simple, but belies the fact that there is also an awful lot of wood to remove.


I started by cutting the step on the beam that receives the rod tenon. For this joint I was using my 240mm ryoba, which felt a bit small at times when cutting the full width of the stock. It definitely had issues with gullet clogging on this resinous wet wood.


I cut most of the cheek on one side of the tenon before I realized that I was missing the lines on the shoulder that allow the tenon cheek cuts to be finished.


After adding the missing lines I ripped down to the second shoulder line on both the tenon and the haunches on the side. From there the rest of the waste was chopped out and the layout completed for the mortise that receives the opposing rod tenon.


The arrangement of the sachi-sen in relation to the draw pin was not clear in my mind, so I stopped the cutting to finish the layout. I still don’t think I have everything in quite the right place, but with this arrangement the wedges are driven first and then the square peg locks the wedges.


Both sides of the slot for the sachi-sen are tapered such that the total taper is 1:12. It was quite convenient for me to add a line on the top of the beam that I could re-set my bevel gauge to when it came time to make the wedges.


My brace is a total piece of junk, very difficult to use accurately, and I broke one of the jaws during a stupid fit trying to use it as a tap wrench. So the mortise was chopped with a bench chisel and the slots for the wedges pared in with chisel as well.


The beam with the rod tenon was next, but I was getting tired and zoning out a bit so I forgot to take many pictures. Rip away!


And voila! It is  cut. I wish…imagine if this was an 8×12″ beam, now that would be some cutting.


Its pretty easy regardless of the specifics of how your wedges are dimensioned to determine the thickness of stock needed.


I noticed the last time that we used sachi-sen that things looked a little miss-aligned after the wedges were driven. I had a line on the rod (which you can see on the right) which represented where the tenon meets the opposing beams shoulder line. This was my reference for a slight offset of 1/32″, same concept as offset for a drawbore. With small little practice joints like this I have the luxury of a trial assembly to see how accurate I was marking the offset from the shoulder line.


Chopping the mortise was easy in this green lumber, but getting the waste out was not. That’s the way of it will all chisel mortising, the cutting is easy and then you spend half your time cleaning.


I ended up with live edge corners on the beam pieces that I felt would look wrong if I didn’t scribe to fit. That’s the reason why the tenons were cut before the mortise.


The stopped rebates that house the beam haunches came last. I was getting seriously fatigued at this point and cut off one of my scribe lines without noticing.


I have a nifty little router plane but I do these exercises with as simple tools as possible to better reflect the conditions I’d actually be working under if I were to travel and cut a timber-frame.  Paring blocks are great! Accurate, pretty fast, and dead simple.


The scribing on the side I didn’t over cut came out great, it looks very craftsman like. This blue stain lumber takes a nice polish from the plane as well, I can imagine having a structure made from it would be a pleasure to the eye.


I did a better job with the wedges this time, even though it took two tries to get the proper fit. I’ve really nailed down what will work for me and I’m glad to have another chance with the sachi-sen. The measurement for the width of the wedge at the top is between the obtuse angle corners of the parallelogram. For the first pair I cut I measured across the acute angle corners and the wedges were too loose.


I thought that I would make the width of the wedge 1/16″ more than needed but that was wrong as well. This is how much stuck out after lightly seating them and I was a dumbass and tried to drive it home anyway. The offset of the slots mean that the top of the wedge width should be the finished width of the slots after the offsets are pulled together, no need for extra relish on the wedge.


They drove about half way and then no further, with a small split starting in the rod tenon on the left side. I tried to get them to back out by tapping around them with a wood block and hammer, but they were seriously, um, wedged in there. It really removed any doubt in my mind about the holding power of wedges. I had to grab the top with a c-clamp and hit the clamp with a hammer, really hard, to get them free.

I know how much of the wedge I want sticking out the top after it is driven fully to depth, 1/8″. After the sweating moment getting these buggers unstuck I sat down for a moment of reflection and thought it through. If the ratio is 1:12 and my offset for the joint is 1/32″ how far down will the wedge travel to bring the pieces into alignment? Twelve times 1/32″ is 3/8″, plus the 1/8″ of extra to stick out the top tells me that the wedge should seat down under hand pressure with 1/2″ remaining before driving in with a hammer.


After planing down the wedges to make the necessary correction I met with success. The offset didn’t pull in completely, and my wedges still look a little sloppy, but the joint is solid. And now to really kill this joint…


Back comes poorly made $20 brace to bore a hole for the square peg. Why is the peg square anyway? I’ve never read an explanation for any advantage over a round hole.  I bored through half way from either side using a small square and my layout to keep the bit in line.


And with a good deal of fuss the hole was chiseled square. I used a screwdriver to knock the waste out, but a strike through chisel of the right size would have been better.

I gave the leading 3/4″ of the peg a very light taper on all four sides so that it wouldn’t blow out any end grain exiting the other side of the hole. My pin was also planed to be a tight fit on the end grain and a running fit on the long grain on the hole.


I left the pin protruding slightly from either side and chamfered the edges after trimming to length. This is a handsome joint, is it not? Took all day and then some of this morning to cut, including ripping the 4×4 beam.

Yesterday was a twelve hour work day to get this far and the theory part of this weeks etude remains, but for tomorrow after a day of rest.