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.
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.
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.
Evidently a t-shaped cut nail by the looks of the damage to the bearing board, haha.
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.
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?
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.
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?
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.
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.
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.
And of course, the piston board is wrapped with raccoon fur, probably attached with rice glue.
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.
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.
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.
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.
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).
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.