Category Archives: Fuigo

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.

Fuigo Fun Shou Sugi Ban

I’ve been wanting to show the fuigo in operation, but have yet to get a dark enough work space set up to judge metal temperature. How about some shou sugi-ban? Needs to be done outdoors anyway. The mass production way to use this technique is with a large propane torch, but there’s something special about a large hot chunk of metal.  After shooting this video I used the last of the forge fuel in the fire-pot to cook a hot dog. Bon Appétit!

Did I mention that I can’t stand the sound of a shop-vac blower? This fuigo is bliss.

The Fuigo Joinery: Part V, The Finish

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Sometimes I forget to show things that I think are too commonly understood, but the humble shooting board deserves a mention. When I first read of this tool in one of Tom Fidgen’s books it was like a revelation. Seriously, how does one get on in the shop without a shooting board? I’m still using my push style board on top of my planing beam because its already been made, no need to waste this one just to be pulling a plane across the work. And this little low angle block plane with adjustable mouth is exceptionally effective at end grain work. Here I’m trimming the piston head board to length.

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I use the wedge from my shoulder plane as a template whenever I’m cutting mortises that will be wedged. For some reason I felt like laying this out with ink, sometimes the ink is more comfortable because its so easy to see, though a little less accurate than knife lines in theory. In practice the more accurate line to work to is the one that you can actually see clearly. I’ve taken to moving around a small work light just to get things properly lit in the shop on days when the daylight is missing.

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After mortising the piston head board I roughed down the handle to a cylinder and drilled the hole for the piston rod tenon.  The handle has to be made first so that the tenon can be fitted properly at the lathe. I decided to make the hole blind, part of the clean look of the fuigo.

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I struggle to make forms that are not ugly at the lathe. If you asked me what looks good in terms of curve and form I couldn’t tell you. Its much easier to say something is ugly and keep removing wood until it looks good, that’s generally my approach. I may have looked at half a dozen pictures of fuigo with these handles, but you don’t really see the form until you make one for yourself.

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The piston rod, having previously been squared and cut to length, was mounted with a two jaw chuck. When I was drawing the plans for the fuigo, this is one of the design constraints for total length of the box. This lathe may suck but it does have some decent bed length.

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The chuck is holding the wedged tenon end, with the handle end against the tail stock so that its easy to check the tenon fit on the handle without unmounting from the lathe. After roughing down to a cylinder I used my parting tool and caliper to cut down to 1″ diameter along the length of the cylinder.

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The cut that defines the shoulder between the square cross section and the cylinder is a good example of the different quality of cut between the parting chisel and skew chisel. Basically the difference between cross-cut and rip-cut.  The tip of the skew chisel, although it makes me nervous to make this cut, gives a beautiful clean end grain cut without tear out.

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The skew chisel, with hand as steady rest, was also indispensable for smoothing down the cylinder to final dimension. I made a gauge block for the bearing ID so that I could check the piston rod without dismounting from the lathe. The final bit of fit was brought in with 220 grit sandpaper, so that the bearing gauge ran smoothly over the piston rod.

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With the lathe work done I cut the tenon and marked for the wedge that secures the face of the piston head board. I used the tenon cheek cut-off to support the tenon as I mortised.

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Mortise cut, tenon chamfered, looking good.

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I had a little scrap of walnut that was the right width for the 1/2″ wedges, so it makes some nice contrast, though you’ll never see it in use. The piston head board was from flat sawn stock, so it cupped a little. I placed the concave face on the side opposite the wedges, just seemed to make sense like that. Eventually the handle will be drilled for a cross-pin, but I don’t want to do that until the piston is fitted to the fuigo because the handle has to be off to take the rod out of the box. I also shortened the piston rod by 1/2″ from the plans so that it would actually fit in the box. As you can probably imagine, the piston rod and head board have to be wedged after assembly while inside the fuigo.

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I would love to find some kind of fur to use as the gasket material, fur is probably the better material because of its natural slickness and fuzziness. As it is I really want to get this thing working, and I can always replace a thin gasket with a thicker one later. With a pair of calipers I measured this towel to be 1/16″ at full compression, 3/32″ in use. So each side of the piston head board was reduced 3/32″, with the exception of the bottom which I only reduced 1/16″ because the gasket material will compress more under the weight of the head board.

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The fit turned out to be quite good with the clearances I guessed for the gasket material, perhaps a little tight top to bottom, but I’m going to see if that changes with a bit of use once the piston is “run in” a bit. All of the internal wooden surfaces in contact with the piston head received two coats of paste finishing wax to make the action nice and smooth. Even as careful as I was with drilling the piston rod bearing and dimensioning the piston rod I still had a little binding towards the back of the stroke (when the rod is pulled out all the way). I could have adjusted the bearing, but in this case just hand sanded the bearing rod until it ran smoothly along its length. I finished the piston rod with a coat of paste wax as well. The lid is simply held on with a snug fit, I didn’t see the need for fasteners.

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And here it is, ready to breath life to a forge. It feels a bit tight, but I’ll wait to make adjustments until I use it a bit. I still need to pin the handle to the rod, but its tight enough at the moment that I’ll wait. It pushes some serious air! I am deeply satisfied with how this project turned out, I totally disregarded the length of time it took to complete. Now, looking at the finished object, it still amazes me that I have one of these, I almost don’t believe that it works so well.

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If you’re into these fuigo you’ve probably read about the gentle woosh of air, the calming click of the valves. The only thing I can compare it to is the meditative quality of shishi-odoshi used in Japanese gardens.  This bellows is the quality of a professional tool, part of me knows I’ve made something too good for me, I aspire to be worth using it.

Next comes making a charcoal kiln for proper softwood charcoal. And perhaps, if my vision stays clear enough and I can train enough carpenters, a small building to house the forge, like Mark has imagined here.

The Fuigo Joinery: Part IV

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Welcome back! I’m working again on the fuigo, a traditional Japanese wooden bellows.  They’re quite simple in design, but not commonly made by skilled woodworkers here in America, usually by blacksmiths and aspiring swordsmiths, so the joinery element can be a bit undeveloped. Don’t fear the joinery, its a question of durability, not just aesthetics. Its occurred to me more than once during this build how powerful a tool is the hand plane, kanna, that it can handle such large and wide material at such a moderate cost. I’m looking at planer/joiners right now and its not even worth my money to get a joiner smaller than eight inches. Because of my hand planes, I can afford to wait for the right beast of a machine to come my way. Who knows if it ever will?

The photo above is the tuyere bearing block with its hole cut, being used to mark the hole in the birdhouse side. I had meant for the tuyere bearing block to be a bit wider, but there was an error in my plans concerning the internal width of the piston box. I cut both the piston rod bearing block and the tuyere bearing block from the same length of stock, and had to switch them around to have a usable piece of wood after cutting the piston rod bearing block too short.

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If I was being super traditional about every detail I would be nailing these two pieces together. As it is, I find screws to be friendlier to the next person who’ll have to work on this. To keep the outside of the fuigo looking clean and unencumbered by a bunch of screws I hid as much as possible on the inside face.

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The piston rod bearing block was next. I clamped the block in position on the side. Previously I bored a pilot hole in the side where I wanted the piston rod to come through.

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With the proper position maintained by the clamps the side was removed and drilled from the back for screws to attach the bearing block. I also drilled through my piston rod locating hole so that it marked the bearing block.

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Boxwood anyone? This stuff is very dense, one of the better bearing woods after ironwood. I cut myself a small piece to inlay into the bearing block.

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Working on small pieces at the planing board can get difficult because there is not enough room to place your foot directly on the piece. I had to use my heal to hold it against the planing stop. This is probably the widest mortise I’ve ever chopped, full width of my 48mm chisel. I cleaned to depth with my router plane, though it was a little large for the blade to work in such a small space.

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With the mortise cut I used my shooting board to trim the boxwood bearing to a perfect snug fit against the end grain. Hopefully when this bearing shows too much wear, probably after I’m dead, the next guy will be able to pop the old bearing  out without any trouble and source a replacement.

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With the bearing installed I re-mounted the bearing block and centered the whole affair on the drill press table for a 1″ hole with a forstner bit. It is really, really important that you get a good straight hole here, so that the piston rod won’t jam and you maintain as tight a fit about the bearing as possible to minimize air leakage.

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And here it is, the finished bearing, cool! I had considered using a piece of steel pipe, or copper, brass, whatever. Compared to buying a brass bearing the nine dollars I paid for my little chunk of boxwood will make a LOT of different bearings. I’ve used wooden bearings on bobbin winders, spinning wheels, they’re awesome.

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With the bearing blocks finished I took apart most of the fuigo and installed the glass across the bottom and the piston stops. Notice the length of the piece of glass relative to the length of the fuigo. For a while I wondered why you would sacrifice the length of internal displacement and put a shorter length of glass in the fuigo than it could handle. The reason has to do with the piston rod bearing, and the tolerances that you can achieve. Just as with a spinning wheel’s bearings for the wheel, you want your bearing points to be as far apart as possible. By using a shorter length of glass and placing it as far toward the back as possible you insure that the bearing rod is less likely to bind in the fully pulled back position.

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Installed the flapper valves. This thing is starting to look like a proper machine!

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I reassembled the sides and found a stupid error. When I originally installed the birdhouse side to mark the  bevel on its top edge I tapped it in with a block and hammer. What I didn’t realize was that the tapping with a hammer caused the sides to pop up a little bit. Thus the birdhouse side was made too wide. I had to go back and plane it down, definitely an error I’ve learned from about assembling cabinetry. The birdhouse side was just a tight fit, to get it back out I had to tap on the bottom board like backing out a plane iron

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In any case it was an easy mistake to fix, and I soon had the birdhouse top installed with some screws through the face.

I finished the fuigo up yesterday, this post is just getting too long to show it all at once. I don’t have a tuyere pipe yet, I’ll definitely need to shoot some video of this thing breathing life to a fire once I get it set up. Stay tuned!

Oh, Sebastian just posted some drawings by Mark Grable for an Open Source Forge. Really beautiful work Mark, inspiring and at just the right time, thank you.

The Fuigo Joinery: Part III

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I finally decided to try a whole systems approach to working with the kanna and nokogiri. My planing beam is angled, my saw horses are low, and my butt stays cool on the ground. I love how much space I just opened up, the floor is much  more visible.  Now, I’m not sayin I’ll never get to making a western style bench, but the possibilities of the tategu’s work space must be explored if I want to really understand the efficiencies to be gained .

At the moment most of my hand tools are hanging or sitting on my pair of trestles, but they’ll soon be moved as well. With my tools in an honest to god tool box or hanging on the wall I’ll once again have use of the trestles and the space for a couple of planing  beams that will allow others to work in the more traditional standing bench fashion.

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Now it is live or die when it comes to cutting while bent over at some odd angle. It is frustrating and difficult at times to limit myself in this way, but in the end will be liberating to have the skill not to need a bench vise.

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Haha, this f**king fly. You know, there’s always something trying to distract you. Hopefully you don’t swat at the flies that land on you with your hand still holding a bench chisel, I’ve done that.  This insolent little insect posed for a couple of photographs before I got back to work. Speed in craft is more about working in a very focused manner than merely moving about quickly. Something is always trying to ruin your ability to stay calm enough to concentrate, this fly personifies that very well. Stopping to take a picture of the thing that’s distracting you? Evidently I’m hopeless, but perhaps you can commiserate.

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Oh, right! I’m supposed to be writing a post about the fuigo joinery…Ok! I finished the sides, more cross-grain dado and routering.

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This is about the most complicated bit of joinery on the whole thing.

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For the little flapper valve covers I marked the dimensions of the opening it covers so that it could be used as a template for marking the holes on the sides.

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The flapper hinges across the string holes by tapering the end. I wasn’t sure just how much to allow them to hinge, but its something that’s easy to change if it feels like there’s too much resistance to the movement of air.

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The battens that form the feet on the bottom were screwed on from the bottom. For the top I secured them with screws from the beneath to keep things looking nice. Both the bottom and top pieces had warped a little and these battens will go a long way towards keeping things flat. Perhaps if I build another they can be attached with sliding dovetails.

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The alignment of a lot of my joinery was not so great, necessitating quite a bit of fitting to get things to line up properly. For some reason it didn’t occur to me to make a story stick for the critical dimensions lengthwise or across the short edge. With shoji work it is really straight forward to mark pieces together all at once, or to use a frame piece to mark the associated kumiko. With wider paneling it doesn’t make sense to mark them together, but a story stick will keep you from measuring twice and marking slightly different each time. My biggest error presented on the thin side panels, where I used my sashigane to square the edges. I failed to check that the length was the same top and bottom, and the top edge ended up being a bit too long for a good fit. Good lesson to learn, I simply don’t have enough experience with tansu.

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As a result, when it came time to put the top on, it didn’t fit! I had to widen the groove in the top that houses one of the short edges by about 1/32″. It will leave a gap on the inside, the gods of joinery will mock me .

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None the less it is starting to take shape! I can’t believe I thought this thing might be too small at 36″ long. At this point I’m ready to cut the glass that sits across the bottom and start thinking about what I want to use as gasket material for the piston head. Its exciting when you finally get to put the stack of carefully cut parts together, it has presence and life. I can already imagine using it, the gentle woosh and click of the valves.

The lesson today was definitely to use a story stick, every time, all the time, whenever you can. It doesn’t matter what the hell the measurements are so long as they are consistent.