Designing a Japanese Timber Frame

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Hello!

I’ve been asked where my daiku endeavours are headed after my study trip to Vermont. Seems like one thing keeps leading to the next, which is nice, and I’m always trying to learn new concepts and expand my knowledge. Among the odder things of late was being asked to interview for a Japanese reality TV show, “Who wants to go to Japan GP”. I’d love to travel to Japan one day, but it will be under my own terms, and this summer finds me far too interested in other things. I think I like a challenge, and buildings are often a series of problems with, at first, no perceivable solution.

Designing a Japanese timber frame is  daunting for the first time. I find myself staring off into the distance visualizing framing details in section view, re-reading for the twentieth time construction details in various books, and pacing back and forth trying to visualize what it would be like to walk through the structure.

To make it all come together requires a set of plans. I’ve abandoned the computer drafting and put together a drafting board and T-square, and borrowed my mother’s set of drafting instruments. (Ain’t it great to have a mom with shit like that? Love the woman.)

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These are my text references. The two western books were my sources for understanding load/span calculations. “The complete Japanese Joinery” and Engle’s “Measure and Construction” are like two sides of a coin, old and new. Odate’s book is just fucking excellent (although its Engle who will show you fusuma, amado, and the all important tobukuro (amado closet).

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For a frame of reference, this is where I’m starting from, a hole in the ground, half into decomposing granite bedrock. It will be a cellar, and I’m basically putting a little 10’x12′ shed over it.

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The greenhouse was built right up next to the cellar hole, not enough room to get a small excavator in there anymore. It means taking material out by hand as the walls are chipped plumb in preparation for a re-bar reinforced concrete slip form masonry wall. I like to think I’m getting a little smarter as I get older, and put together a small counterbalance lifting device for getting the material out of the hole .

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It sits on a post with a level cut on the top, rotating on a pin made out of re-bar. The pin for the lifting arm is oak, it only took a couple of hours to put this together and has helped tremendously.

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I have to deck over the whole cellar hole and provide enough depth to insulate the ceiling, so the total deck footprint will be about 15’x16′.  It doesn’t gracefully fit the ken building unit in traditional Japanese measure, which is about 6′ centers to the posts, but I think I’ve been able to come up with a balanced design.

In the above section view from the south elevation you can see that the big deck allows for a veranda, which will also wrap around to the north side.

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There will be two sets of shoji, adjacent to the NW corner post.  Amado will cover the north and west veranda, an important element to keep from needing a drainage plane to protect the insulation infilling the floor joists. I also tried to design the roof to utilize available lengths and widths of metal roofing, but the effect of insulating the roof threw off my proportions on the west side and I had to extend the roof edge one foot to restore balance. I’ve been playing around with ideas for diagonal bracing too, I have to design for 130mph wind gusts and I don’t have certainty that nuki (half dovetail wedged horizontal bracing between posts) and good joinery will be enough to resist the shear forces imposed on the sides of the structure and ample roof margins.

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I designed the floor system first, with much use of the cogged lap joint for the floor joists. The floor boards of the veranda run parallel to their length, and meet up partially with a mitered edge at the corner. This Japanese habit of stacking structural  floor elements on top of each other works to my advantage in getting enough depth to properly insulate the ceiling of the cellar. Although from what I can tell it is a departure to have the main floor joists in plane with the ground sill. The foundation will provide a knee wall to get the ground sill above grade in any case, so this stuff gets a bit fuzzy at times, you just have to make it work with what you need to build.

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Insulating is another area that requires thought. I love the way the traditional clay infill looks, keeping the structural elements exposed is much less of a concern when you have an ample roof overhand protecting the building. That said, it gets pretty cold here in the winter, and if I want the structure to be habitable in the cold months a little insulation will go a long way. The rafters and decking of the roof is visible on the interior, a nice element I wasn’t willing to give up for thermal envelope, so it means insulating on top of the roof deck.  It creates a pleasingly thick roof edge, and even without a fascia board on the gable and eave ends covering the rafters can be used to create an interesting edge profile.

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The gable roof framing is straight forward, the beam dimensions determined mostly by the loading and deflection requirements of the cantilevered overhang of the roof edges. Unfortunately I forgot to space some of the outer posts for the amado closets! On the west veranda it doesn’t change the loading much, but on the north edge I’ll have the noki geta beam carrying quite a bit more of the roof load from the ridge and purlins posts. This drafting work is time consuming, and I knew I’d probably have several design revisions.

Yesterday was frustrating in that regard. Okay, I see I need to move some posts, but where to put them. Okay, design the amado closet. Oh, wait, you need to know how thick your amado will be, how many, how wide. Oh, right, need to figure out a design for insulated amado that don’t look thick and ugly with insulation showing inside the veranda…

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The walls present the greater insulation challenge. My posts are all 5″x5″ and don’t leave much room for insulation. I’m hoping that an EIFS system stucco with mechanical attached fiberglass mesh over poly-iso  will work.

There’s still much design work to come, for now I’m pleased to finally have some of my ideas to scale on paper, its a good start.

Studying with Yann Giguère of Mokuchi Woodworking

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I managed to sneak in a few lessons between his busy production schedule with Yann Giguère of Mokuchi Woodworking in the Bushwick area of Brooklyn, NY. Yann undertook a nine year apprenticeship in traditional Japanese carpentry with Dale Brotherton of Takumi Company, and there are few people more capable of teaching hand tool skills and passing on knowledge than Yann at the moment. Interestingly enough, Yann was also there in Iowa when Yataiki was teaching, and I heard about him from a traveling shakuhachi musician/carpenter Max Citron who visited with a trove of great photos and video from Takenaka carpentry museum while I was in Vermont.

What a great teacher! Like most of the people you’ll meet that work in this field Yann showed a total lack of pretentiousness or aloofness. You might imagine that we dived right in to the intricacies of koyabari, hip roof layout, and joked about the frustrations of kumiko-zaiku work. However, of far greater utility was working at the fundamentals of good carpentry; marking, sawing to a line, sharpening, and tuning kanna. I could have spent three times as long learning this and not have gotten it all.

For example, even more than discussing what a good layout looks like we started with exploring the sumisashi (bamboo ink brush). I’ve made a few of these in the past for marking logs to saw to boards, but approached their use with a admittedly western mindset, placing the bevel on the wrong side of the pen for right handed use. You see, I was assuming that the greatest accuracy came from holding the marking tool plumb against the straight edge. The reality of this is that you can’t very well see the line that you’re marking, and tend to draw less than straight lines. Ever wondered why your marks don’t come square around a piece you’re marking even though you know the piece is perfectly square? By holding the bevel edge of the sumisashi against the square you’re hand is out of the way allowing a clear view of the work.

And neither in this regard did Yann have a slavish attitude of adherence to one particular marking instrument. In his shop at the time was a bunch of white ash being joined into a low bed for tatami, marked with pencil because the ink might bleed into the open pores of the wood and require too much material be removed at finish planing to remove the marks. So too did I see a nice selection of left and right hand marking knives.

Next, having myself had the need to show the use of the hand saw, I was greatly impressed to see the ease and naturalness with which Yann let the saw work. We discussed the problems I’ve seen in my own work with producing flat sawn surfaces, mostly related with pushing the saw too hard into the cut and using too dull of a saw. You might expect that Yann used only the highest quality saws, but everything of what was demonstrated to me was quite intentionally with saws of the disposable blade variety. And he had quite a nice collection of hand made saws.

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Including three maebiki-oga, one of which you can see in the background!

We covered snapping lines with sumitsubo, Yann demonstrating how, and why, to snap curved lines by twisting the ink line. Most of my last lesson was devoted to sharpening and tuning of kanna, which opened my eyes on what good sharpening looks like, and its not like I’ve failed to spend my fair share of time learning this skill. Will I be able to sharpen while squatting on the ground? Lets find out…

I feel ready to make my first foray into Japanese structural carpentry now, for better or worse, daiku means action and practice, and I can see the road ahead quite clearly.

Even in the short period of time I spent at Yann’s shop I learned more than could possibly be discussed in a simple blog post, and that would miss the point in any case.  Having come from a fine music background previous to carpentry it was not hard for me to appreciate the relationship of student and teacher for the direct transmission of knowledge. Some things are still most easily communicated person to person.

Imagine then a gathering of many skilled carpenters! Kezurou Kai NYC will be held August 26-27, 2016 in the Bushwick area of Brooklyn, NY. Last year Jim Blauvelt won the planing competition, and he not only cut the dai he used, but forged the kanna! Want to go?

 

From Tree to Something to See

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Well, I’m heading home to Colorado for the summer by way of Brooklyn to visit Yann Guigere of Mokuchi Woodworking, which has given me some time to catch up on the last stuff I worked with Mark in Vermont.

The last bit of joinery I cut was a ramp for a deck, and it gave me the chance to use some of the Black Locust I sawed to boards at the beginning of my stay. The slope of the deck to the ground wasn’t enough to justify stairs, but the construction was similar, using wedged mortise and tenon and a sliding dovetail at the bottom of the stringers. I used a 6-3/4″ Makita planer to smooth and square the lumber prior to layout. God I need one of these machines! And I got to play around with a Hitachi hollow chisel beam mortise. The stringers I was mortising were too wide to seat the mortiser properly, so it ended up being faster to simply drill and chisel the mortises, but man, what a sweet machine.

This lumber made a bitch out of my disposable blade saws, by the way. I wouldn’t have been able to saw the tenons without some of Mark’s big ryoba nokogiri.

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The stringers for the ramp were live edged, with a beautiful curve that really fit the naturalistic round timber element of the deck railing. Everything cut, of course, to a center line.

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The locust was still very green, so I tried to cut the wedges extra long so they could be pounded in further as the wood dries, but also took the measure to back the joinery up with a few screws toed in on the inside in case someone failed to do so. I never seem to cut long enough wedges, in the future its a safer course to just make wedges several inches too long.

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It would have been nice to attach the ramp with sliding dovetails to the rim joist of the deck, but the decking was already down so it was attached with your conventional hanger and screws, landing on some local stone for a floating foundation. A heavy coat of Linseed oil/pine tar/turpentine finished things off and will help control the drying now that its in the sun, and Mark helped me chisel the corners to round and touch up a few details.

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We took a break at some point and went over to the neighbor who now owns the farm that was part of the property that Mark’s on, which has an enormous old timber frame dairy barn that is in places still sitting on a dry stone foundation. It had very workman like construction, no superfluous details, and it was great to see a timber structure hold up so well in wet Vermont.

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Back over at the house we finished up the railing.

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It was my intention when I first traveled to Vermont to help Mark cut the frame for his forge, but the universe is a funny place. And three months is only enough time to scratch the surface of saw making. I’m heading back to Colorado to take care of family and help my mother cut a small structure, keep her property development moving along as we permaculture the shit out of the place in the hope that it will help secure a sustainable future for friends and family. Being with Mark, a gentleman and a scholar, has changed how I approach my craft, in ways I am sure to still be contemplating for many months to come.

And, I left Mark with the beams of lumber for the forge frame stacked in the right order and ready for layout and joinery. My hope is to make it back out to Vermont in the near future and finish what we have started, and see this knowledge preserved for the next generation and beyond.

On another note, I’ve been drafting the fuigo plans based on Hirota’s fuigo, but have been unsure of the best way to present the material to people that want to make use of it. My free trial of Adobe that allowed me to make .pdf files has expired, so I would need to either publish a design thread with illustrations from sketchup, up simply make the Sketchup file available for download. I’d like to hear from people what would be the most useful format for a set of plans, please let me know.

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Brought to you by a happy woodworker.

Hirota’s Fuigo

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Interested in making a fuigo (Japanese box bellows) for your forge? Mark Grable has an old fuigo from a saw smith friend of Yataiki, Hirota. This is the fuigo that John Burt used to build a copy for Yataiki in Iowa, and its worth studying if you want to build your own because there are many technical refinements in shape and joinery that are very important to how the bellows is used, especially when it comes to pumping the bellows with your foot during yaki-ire.

I’ve made a fuigo myself, which you can find by searching the fuigo category on the left of the page. If you’re not too familiar with their construction your understanding of the following details will benefit greatly by reviewing and watching the John Burt video.

I’ve seen a lot of modern fuigo at this point, that while quite useful and functional, fail to meet the potential of what this tool is capable of as part of the total context of how a Japanese smith would work at the forge. The most common thing I see lacking is size, this fuigo measures nearly four feet long, with a total length of 116cm, and an internal displacement cross section of 25cm wide by 56 cm high.  Its made from top quality vertical grain Japanese cypress. The top and bottom are each a single board, and the long sides are made from two boards joined together.

Understand, fuigo are made in many different sizes, all the way from the monster bellows used in tatara production of tamahagane to the tinsmith’s tiny backpack bellows, but its worthy to note that Yataiki asked Burt to make a fuigo three inches wider than this one. By comparison, the fuigo that I made for my forge is about three quarter scale of this one, due primarily to the constraint of needing to store it out of the way on a shelf while not in use.

 

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The handle fits on a tapered round tenon, with the hole drilled in the handle at a slight angle so that it faces the smith more directly. In addition, there is the all important foot board on the piston shaft. This is what the toes of the smith’s foot rest against while pumping the bellows with the left foot, leaving both hands free to manage the coal bed and manipulate tongs.

Notice the groove that’s been worn in the handle by so much use? Respect.

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I originally thought that this board was simply held from slipping up the shaft by the taper of the tenon, but in this case it is evident that a nail was used to back the foot board up.

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Evidently a t-shaped cut nail by the looks of the damage to the bearing board, haha.

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In fact, the whole fuigo is assembled with nails, with some very interesting nails with an extra wide head used on the sides and birdhouse top.

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Another important detail is the curve to the sides. Its easy to say that the fuigo sides are curved both in length and height, but how much?

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Finally I can measure a working fuigo to get my answer, and it surprised me a bit. The long sides have a total deflection at the center of 5mm, and the total deflection of the height along the short sides is 2.5mm. Further more, the long sides taper in along their length 10mm! If the need for the curve to the sides can be ascribed to counterbalancing the internal pressure of the air bowing outward, perhaps the taper is due to the action of the foot pumping the bellows with a limited stroke with the piston rod almost all the way to the back of the fuigo.

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Looking at the bracing on the top I have often wondered why the front is boxed in, still not sure, but I do notice is that the battens are nailed only on the outside edge where the nails will come through outside of the dado’s that house the side panels. On the lower left there’s quite a depression that has been formed, perhaps by many years of a hand resting on the corner?

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Looking at the bottom of the fuigo top we can see the dados. I placed a straight edge against the outside edges and they have a bit of curve to them as well, not as much as the dado’s themselves, but just about what you would expect if you first planed the curve on the outside edges and used them as a reference for marking the grooves with a gauge, and then made the outside edges a bit straighter during finish planing.

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You can still see the saw kerf at the bottom of the groove from the azebiki nokogiri that was used to saw the dado lines. Haha, not too fine of a cut at the bottom, pretty much chiseled out quickly.

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One of the more subtle refinements is that the top edge of the sides as well as the dado’s in the top board that house them are tapered. After all, the top board is secured with only a pressure fit, but still needs to be removable and create a good seal against the internal pressure of the air when pumping the fuigo.

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And of course, the piston board is wrapped with raccoon fur, probably attached with rice glue.

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And the front stop for the piston head is about one third of the way down the fuigo. My guess on why the whole length of the box isn’t used has to do with the length of stroke that the human arm is capable of while seated, as well as the need to keep the piston board from jamming on the push stroke by keeping the bearing points separated by a bit of distance at all times. The piston rod bearing wasn’t a great fit, but that probably had more to due with the wear this fuigo has seen than any design consideration.

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A lot of the chamfers on this fuigo are shallower than 45 degrees. For example, the chamfers around the flapper valves that let the air into the bird house leave 5mm of side thickness untouched, when the total thickness of the long sides is 9mm.

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Although, the front and back flapper valve holes are not chamfered, not sure why. There is however gasket material sewn on to the front and back of the flapper.

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The dado’s on the top aside, the quality of the fits on this fuigo suggest that whoever made it knew what they were doing. Take, for instance, the fit of the bearing block to the curve of the long side, not a right angle. Similarly the edge birdhouse top is beautifully fitted to the curve of the long side panel, not a gap in sight, and consider that the long sides curve both in length and height.

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The joinery that connects the long side by the birdhouse to the short side is the trickiest bit, a half lap with concurring dado’s that slide together. There’s an extension on the long side that is quite weak, and I had one of mine snap off because of the tight fit of my joinery. It was beautiful to me to see that this had been taken into account by the craftsman by shaping the extension so that less wood rubbed against the short side panel (although there was still a crack here, haha).

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The last detail that I’ll discuss today is the air exit that connects to the carved kiri tuyere. Its tapered to fit the conical section of the kiri tuyere adapter, and also angles slightly towards the front of the fuigo. Why the angle? Perhaps it has to do with the length of the fuigo relative to the placement of the fire. The hole is also not centered on the length of the fuigo, lying slightly towards the front.

I hope this information is of use to those making fuigo for their forge. I took a complete set of measurements and drawings in metric which I’d like to draw up into a set of plans. Let me know if you have any questions, I’ll do my best to answer.

Sen and Sen-Dai for Hand Scraping Saws

 

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This is going to be a post with a lot of pictures, hopefully it won’t take forever to load on your web browser. To start, a method for measuring saw plate thickness, basically a red-neck deep throat dial micrometer using a drill press. By setting the zero on the dial to the thinnest parts of this saw I could write the deviation in thousandths directly on the plate, a grid of numbers. Supposedly this kind of saw plate variation of thickness for western panel saws is unusual, but it offers me a good opportunity to discuss the Japanese tools used to hand thickness nokogiri.

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With the grid of the saw mapped I built up a topographical map to better visually represent the variation in thickness. After all, if you’re going to scrape a saw evenly you need to know where to take off metal. This saw already went through quite a bit of hammer straightening, but the problems with the uneven thickness of the plate are making it difficult to get that last 10% of straight. The normal fashion for gauging proper thickness on Japanese saws is to bend the saw and observe the curve, and I can attest that this is, with appropriate experience a la Yataiki, an extrememly accurate way to thickness saws to within a thousandth of an inch, based on some of his saws that I have looked at with the dial micrometer.

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The tools used to scrape the saw plates are sen. You’ll find that these were once very common tools to all of the tool making blacksmith trades, including katana and kanna. Some of the sen pictured here are specialized for saw making, like the one at the very bottom of the frame, but there are others that could be used for hand scraping the ura (hollow) on the backs of Japanese chisels and kanna, or the flute on the sides of a katana.

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This particular set uses laminate construction with Swedish steel.

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And the final stage of scraping involves a lot of work hand burnishing the surface with a lot of pressure and elbow grease.

What kind of Swedish steel I would very much like to know, seeing as saying Swedish steel is about as useful as saying they are made from high carbon steel, there’s a lot of different kinds out there these days.

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Lets start with a frame of reference for what the hell I’m talking about. This is a photo of Yataiki thicknessing a saw at the sen-dai. Beautiful metal shavings, no? The sen-dai comprises both the board the saw is resting on and the staple vise used to hold the saw flat. The large staple goes over the sen board and is mounted into a foundation block of poured concrete in the ground, a large block about two feet wide by four feet long, very stable.

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For holding the saw down flat to be scraped on the sen-dai there are lots of little spring clamps and wedges. These are all used under the staple of the sen dai. The ball bearing is for rolling vigerously in hand to prevent blisters, the loop of steel is a way of binding the handles of a pair of tongs when forging. The little rectangular wedges hold the sen board against the wedge beneath it that gives it the proper downward angle for work.

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For holding the opposite side of the saw nearest where you would be seated are more spring clamps, elegant little pieces of spring steel that slip over the edge of the sen board.

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Saw makers don’t make one saw at a time, its more of a production affair. Here is a good stock of rough forged blanks, ready for rough grinding after the tangs are forge welded on.

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An elegant spring clamp in use.

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And under the staple the various wedges. The spring wedge holding the tang down has a curl at the other end used as a snell, for tapping the wedge loose.

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This is just a mock up of the sen-dai. There is one size of board for larger saws.

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And a smaller, thinner board for dozuki. Both of these are made from Kashi, Japanese white oak, the same wood used in plane dai.

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The staple spring clamp for dozuki have a variation with a little stop cut at the end that the blade butts up against.

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That allows for working right up to the end of the saw plate.

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In the past all of the thicknessing would have been done by hand. More modern methods involve a rough surface grinding to remove most of the excess material. Here is a ryoba saw, rough ground and tempered. Beautiful colour.

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Apparently dozuki are differentially tempered, softer along the tooth edge.

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What you’re seeing here is a dozuki blade that’s been hammer straightened after tempering with two different kinds of hammers. Fascinating surface!

 

Note: This post has been edited to correct an earlier mistake, referring to Japanese Oak as Keyaki (a type of Japanese Elm) instead of Kashi.