Japanese Tools: How They’re Made
By Garrett Hack
Part two on Garrett Hack’s recent trip to Japan. In part one, read about Hack’s visit with a Master Craftsman and his particpation in a “plane off.”
To the northwest of Tokyo, all the way across Japan, is the tool making center of Sanjo City. I had introductions to two craftsmen there, a maker of wooden plane bodies (dai) and a father and son pair of blacksmiths making all types of edge tools.
Communicating with them was going to be a problem, as few of the craftsmen I met spoke much English. Fortunately, by the time my class ended near Tokyo, I had 4 woodworkers who wanted to tag along, all willing to translate.
The Dai (plane body) Maker
Isao Inomoto works in a modest shop in a line of what look like small factories. Trained by his father, Inomoto-san has been making dais for all of his 70 years. He is considered one of the best dai-makers in Japan, where craftsmen with the most revered plane irons go. Connected to his shop is a storehouse quite literally stacked-to-the-rafters with mostly white oak blanks for a variety of plane models.
The dai-maker’s shop is literally stacked-to-the-rafters with wood blanks.
Whilte Inomoto prefers white oak, he does turn to red oak for certain plane models. There are thousands of them drying with dates scrawled on their ends in crayon, some as wide as 12-in., from thick planks sawn locally. Also in the storehouse is a custom mortiser that chops out the mouth of the production planes he makes, and barrels of oil for soaking the completed bodies.
Inomoto-san works seated on a thin cushion on a wide and polished wooden stage. Between his legs is his “bench” — the top 2-in. of a post that goes through the floor to a firm foundation below. On the wall behind him are his and his father’s tools, and surrounding him are a few squat but heavy machines on wheels that he moves into place when he needs them, such as when drilling a dai for the steel pin that locks the cap iron and blade in place. His wife helps him, making hot tea on a little wood stove she keeps fired.
He works quickly and deftly, laying out the angled cuts for the mouth, and then with serious force and a large chisel, chopping it out in minutes. Grain orientation of the blank seemed less of an issue than consistent even grain, but the grain is usually quarter-sawn and perpendicular to the sole. Cutting the wedge-shaped grooves for the plane blade, fitting it exactly to a very snug fit, and adjusting the mouth took at most 20 minutes. He then drilled for the retainer pin, fitted the cap iron, and sharpened everything off the platform on a few large waterstones set between his legs. The shavings this plane took were streamers—not curls—flying out behind.
The blade he fit during my visit had been produced by a famous maker, perhaps taking months to forge and worth a thousand dollars or more. To me it looked no different than any other, maybe just a bit thicker. Inomoto-san pointed out how the high skill of the maker can be seen in the narrow and consistent weld line of the high carbon edge to the wrought back. This unique Japanese metallurgy has always been a mystery to me, how such blades are made and the unique hollows cut into their backs. I was very much looking forward to seeing the process up close.
The Blacksmith’s Shop
Our next stop was a forge very similar in appearance to Inomoto-san’s shop: spare, concrete floor, metal sidewalls, with a few large machines such as trip hammers for production work. The small forge the son worked at sat on the floor, along with an anvil, a sunken tank of water for quenching, and a box of fine sand for slow cooling the steel when annealing. He stood in a sunken manhole with his waist just above the floor.
To light the forge, the son preformed one of the most amazing demonstrations I have ever seen, hammering a piece of bar stock until it glowed red hot. It took all of 20 seconds, whomping the steel on the anvil with machine gun blows, each time turning the bar a quarter turn. The heat came entirely from the friction of moving the steel, tapering it so rapidly and consistently.
The payoff for all that handwork is one handsome blade.
Making a chisel was less dramatic. Contrary to what you read, the softer wrought iron of the body is not old anchor chain (that was used up decades ago), but a piece of bridge girder. The cutting edge was manufactured yellow steel, quality tool steel denoted only by the color of its paper wrapper. It seems another myth, that of blue vs.
white steel and the virtues of one over the other is simply marketing as well; there is little difference.
Once the son had the wrought body and tang of the chisel shaped, he simply forge welded the yellow steel back on. He sprinkled some flux on the red hot body, positioned the equally hot back on top, and hammered them together. He then refined its shape, cut the hollows in the back, hardened, and tempered the tool. Since wrought iron is low carbon, it doesn’t harden as the tool steel cutting edge does, but remains ductile. Its elasticity and ability to absorb shocks, is one of the virtues of this Japanese method of making blades. Nothing magic here, just basic science.
Hollows by Eye
I had always assumed that the consistent hollows on the back of a Japanese blade were done with a precision grinder of some kind. Hardly. The father just held the back to a very large grindstone and worked by eye. He also demonstrated scraping the hollows using considerable pressure with a spokeshave-like scraper with a narrow curved blade.
The last stop was at the shop of Hirade, a dealer of the best woodworking tools in Japan. Even though it was tiny, there were dozens of different planes, chisels, natural sharpening stones, marking tools, and everything a craftsmen could need. My enthusiasm was dampened only by imagining carrying in my already full pack, anything more.
The workshop of dai (plane body) maker Isao Inmoto.
Blanks carefully stacked at the dai maker's shop.
The name of this very high quality blade roughly translates to "the one that whispers through the wood."
Here, a spokeshave-like shaper is used to carve out the hollow of a chisel. A considerable amount of pressure must be applied to acheive the final result.
Grinding the hollow of a Japanese chisel by eye.
A traditional Japanese blacksmith.