What size steel for a bunka?

A bunka is a tall Japanese kitchen knife with an angled point, and its height is what sets the bar. The preset is a 6 3/4 in blade (about 171 mm), 1.9 in tall at the heel, with a 3/32 in (0.094 in) spine and a 5 in hidden tang for a wa-style handle. Add 1/8 in for clean-up and you need 2.025 in. That is just over 2 in, so it rounds up to the next listed width: 2 1/2 × 3/32 in flat bar. A bunka up to 1 7/8 in tall fits 2 in bar, since 1 7/8 in plus the 1/8 in clean-up comes to 2 in.

The matching KraftyDesign blank (the "Draw this blank" link) is tall, and near the front the spine breaks sharply down to a low point. That angled point is the k-tip. The edge keeps a gentle belly, and the handle hangs off the spine. At about 48 mm, 1.9 in is a normal height. Three bunkas sold by Chef Knives To Go, a knife shop in Fitchburg, Wisconsin, are listed at 172 to 175 mm long and 43 to 48 mm tall. Japanese Chefs Knife (JCK), the online shop of a knife exporter in Seki, Japan, gives 46 to 49 mm for five of its bunkas of 175 to 190 mm.

Spines vary more. Those three Chef Knives To Go bunkas measure 2, 2 and 4 mm at the base, and JCK gives 2 to 2.2 mm for its five. At about 2.4 mm, 3/32 in bar is a little thicker than most of them, so matching them means grinding a little off. The calculator starts on 1084, and AEB-L and 52100 give the same 2 1/2 × 3/32 in bar. 14C28N is sold in metric thicknesses, so the calculator flags 3/32 in as uncommon for it. Pick 80CrV2 and it warns that 3/32 in is under the 0.1 in usually considered practical in that steel, and says to expect warping in the quench. Check what your supplier stocks.

The calculator starts on stock removal for this one. Stock removal takes the whole 6 3/4 in blade and 5 in tang plus clean-up: 12 in of bar per blade. That is about 12 3/4 oz of bar for a blade that finishes around 4 1/2 oz. Most of that difference is the wide bar cut away around the narrow hidden tang. A 12 in bar gives none, because the calculator puts the minimum bar length for this blank at 13 in. An 18 in bar gives one, and so does a 24 in bar. A 36 in bar gives two, and a 48 in bar gives three at the lowest cost per blade.

Forged, the steel is moved instead of ground away. Drawing out the tang and the bevels stretches it, so just under 5 in of the same bar (about 5 oz) is enough. The blade finishes just under 3 1/2 oz. A 12 in bar gives two, an 18 in bar gives three and a 24 in bar gives four. A 36 in bar gives seven at the lowest cost per blade, and a 48 in bar gives nine. At this size the calculator also shows an alert: "Bunka" implies a 2.58:1 draw. Consider thinner stock or a press.

That means the finished blade and tang come out 2.58 times as long as the steel they are forged from (not counting the clean-up allowance), and the calculator flags anything over 2.5. Wide bar makes a short piece that takes a lot of forging to stretch, most of all where it is drawn down into the narrow hidden tang. A bunka up to 1 7/8 in tall comes from 2 × 3/32 in bar, and the alert goes away. Starting thicker doesn't help here: "One size up" under "Forged thickness" starts you at 2 1/2 × 1/8 in, and the draw gets heavier, 3.44:1. The calculator won't forge AEB-L, CPM-154, 14C28N, MagnaCut or A2. Pick any of them and it works out the bar as stock removal, even with Forged selected.

What a bunka is for

A bunka (bunka bōchō) is a Japanese all-purpose kitchen knife. Bunka means "culture" in Japanese, as Knifewear and JCK both note. English Wikipedia says the bunka has a more angular, straight tip than the santoku. Chef Knives To Go calls it one of the most capable all-purpose blade shapes in the Japanese kitchen, and says the flat profile is good at push cutting and the reverse tanto tip adds precision for detail work. JCK lists vegetables, fruit, chopping and fine work such as filleting fish or trimming meat. Knifewear puts bunkas generally at 160 to 190 mm (about 6 1/4 to 7 1/2 in), so the 6 3/4 in preset sits in the middle. Knifewear calls the ko-bunka a smaller version, and Chef Knives To Go sells ko-bunkas from 105 to 150 mm. Bunkas are usually double bevel. JCK says the bunka is commonly found with a double bevel edge, and every retail listing cited here that gives a grind is double bevel. Chef Knives To Go's three all have octagonal wood handles, the wa style that the preset's hidden tang is meant for.

The point is what sets a bunka apart. Knifewear says the cut-off tip of a bunka or kiritsuke gets called a k-tip, and that people who like swords seem to prefer the name reverse tanto. It treats the bunka and the hakata as nearly the same knife, and says you could call a bunka a kiritsuke santoku. Chef Knives To Go also lists a few knives under another name, kengata, among its bunkas. On the American Bladesmith Society forum, one poster describes the bunka as light, thin and double-edged, with a slight curve and a k-tip. That poster says the tip should be tilted back a little and kept really thin. In a BladeForums thread on making a bunka, one reply, from a poster who says they're no expert on Japanese knives, says the opening poster's profile looks a little too straight. It advises planning the profile before grinding the bevels or heat treating, and trying it on a cutting board. The same reply says the tang may need to come down in size if it is going to take a wa handle. In stock terms, the bunka sits between two other BladeStock pages. The nakiri preset is 2 in tall and uses the same 2 1/2 × 3/32 in bar. The santoku preset is 1.85 in tall and fits 2 × 3/32 in.

None of these origin stories comes with a source, so read them as lore, not history. Tojiro, a knife maker in Tsubame, Niigata, says the bunka (which it also calls the kengata) was developed in the Shōwa era (1926 to 1989). In its telling, the bunka joined the good points of the gyuto and the nakiri and cut the tip off at an angle, and the santoku came later by rounding that tip. Knifewear also has both knives growing out of the nakiri by clipping off its tip. It says the bunka likely came first, since a straight line was easier to cut than a smooth curve in the 1940s and 50s. It also says the word bunka was used a lot in 1950s Japan for things with a Western influence, and that American-style apartment blocks were called bunka apartments. Chef's Edge, a knife shop in Western Australia, puts the bunka in the Meiji era (1868 to 1912) instead, made for the red meat and new vegetables coming in from the West. Wikipedia gives yet another reading of the name: that it refers to the cultural food of Japan. English Wikipedia treats santoku bōchō and bunka bōchō as names for the same general-purpose knife. Zknives, a knife review site, also calls bunkabocho another name for the santoku and says it is typically single grind, which is not what the retail listings above show.

Stock for a bunka

In a BladeForums thread on making a bunka, the opening poster roughed out 80CrV2 to about 0.10 in thick for a blade about 7.1 in long and 2.1 in tall, and asked how much to grind before heat treating. One reply says to go to at least about 0.8 mm at the edge, warning that thinner grinds raise the danger of warps. On the American Bladesmith Society forum, one poster describes a bunka they made for a client's wife, a home cook with small hands: about 160 mm long at the edge, 40 mm tall and 3 mm thick.

Widths assume blade height + 1/8 in rounded up to stock; thickness is the finished spine rounded up. Change the inputs above for your own pattern.

Steels that suit it

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