Satou Making in Your Home – Creating a Carving Knife From Samurai Sword Parts
One of my hobbies is carving. Specifically, I carve netsuke and related small objects. A netsuke is a traditional Japanese ornamental toggle that is used to attach a small bag or parcel to your kimono sash. They are traditionally made of animal materials like ivory, boar tusk, whale tooth, and stag antler or wood like boxwood, ebony, and jujube. All these materials are very hard and the knives used to carve them are specialized tools called “satou” or “hidari-ba” which are more like tiny scrapers than knives. They look like dental picks for mythical creatures to be used by monstrous dentists. Traditional netsuke craftsmen make their own tools, because you cannot find ready-made satou knives in hardware stores. I acquired my first set of satou knives from master carver Kazuaki Nakamura but I needed a knife suited to my individual needs: One that was curved in the opposite direction to the knife included in the set. So I decided to make one myself.
I bought some samurai sword fragments from an online auction. It is illegal to own a samurai sword in Japan today without a license. When people find an old sword in an old house they bought or inherited, some of them do not bother with the hassle of licensing the sword and opt to destroy them. It is a shame since there is no telling how valuable some of these swords might be. Some samurai swords found in old attics turned out to be over five centuries old. All the same, a lot of people cut up the precious blades into short bits with angle grinders so they can be legally disposed of. These cut up blades, called “zanketsu”, are actually highly sought after. You cannot find better blade steel anywhere. And, in the case of swords forged before the 17th century, nobody even knows how they were made. A lot of traditional craftsmen use these to make tools specialized for their craft. People also make pocket knives and sell them over the internet. (Consequently, small pocket knives made from samurai sword fragments are available to buy on online auctions.)
So I took the pieces of steel, each about three inches worth of blade length, that might have been involved at some point in killing somebody, and fixed them in a vise. I used an angle grinder and cut off small pieces suitable for my purpose. Be sure to wear thick leather gloves and eye protection when you do this. You do not want an errant splice of samurai steel flying into your eye. Be careful. These fragments may look rusty and blunt, but they can still cut your fingers off.
Since I did not have a forge, I used a shichirin, which is a bucket-sized clay barbecue grill you can pick up at any Japanese hardware store for about 2000 yen. I filled it with wood charcoal and jerry rigged a bellow from a used hair dryer. I intermittently supplemented the heat with a hand held blow torch. I had a tiny shoe-maker-sized anvil and a regular carpenter hammer to shape the metal piece. Once you have a workpiece roughly approximating the tool that you want, you take it to the disk grinder and grind it into shape.
Tempering and annealing took some doing. I first took my finished blade and put it in a stainless steel cylinder filled with powdered charcoal, then blow torched the cylinder from the outside because I read on the internet that this was the way it ought to be done. It did not work. I later learned that you could achieve the same result by just dropping your work into the red hot charcoal of your forge. Wait until the metal is orange hot, keep it that way for 10 to 15 minutes, then dip it in cold oil. The annealing can be done by directly heating your workpiece with your blow torch until just before it turns purple and cooling it gradually, or you can suspend it in heated oil that is hot enough to start smoking (roughly 200 degrees C) and keep heating it for about an hour. I opted for the oil method. Either way there are numerous ways to hurt yourself in the process so take all necessary precautions. Do not do this around children or pets. Once you have your blade tempered and annealed, try sharpening it on a standard medium grain whetstone (#1000 or #2000). If it sharpens too easily, the tempering was too mild. It should be much harder to sharpen than your kitchen knife.
I made a wooden handle from a piece of wood on a mini lathe, drilled a hole in the center, and rammed the butt end of the blade into it. The end result looked pretty good.
I used my newly minted satou to carve a realistic chestnut from a piece of boxwood. I put it in a small dish with some real nuts to see if my friends could guess which one was real. The outcome tells me that my carving knife did its job. It is not as good as the knives made by a master craftsman, and I intend to further experiment with knife making in the future, but for a first time effort, I am willing to say that this was a pretty good result.
In the interest of wildlife conservation, professional netsuke carvers have moved away from using ivory and whale tooth. But they still use stag antler (deer horns) which are renewable resources. (Deer horns grow back every year.) They also use mother of pearl, coral, jade, and very dense woods like boxwood, ebony, jujube, pink ivory, and desert ironwood. These are very hard materials and require durable blades to work on them. Hence you need very high quality steel to make these blades.
If you cannot find bits of samurai swords, you can make your satou knives from “drill rods”, steel stock meant to be machined into drill bits. The type of steel is designated either SK4 or SK95 and available from specialized vendors. They are more consistent than antique sword steel, of which there are some occasional misses as well as rare gems. Master netsuke carver Ryushi Komada makes his tools exclusively from this modern material. He also explains that you do not need a forge to do so and that you can do the whole shaping, tempering, and annealing process using a handheld blow torch. But what’s the fun in that?