What size steel for a deba?

A deba is a thick, heavy Japanese fish knife, and its height and spine both set the bar. The preset is a 6 1/2 in blade (about 165 mm), 2 in tall at the heel, with a 1/4 in (0.25 in, about 6.4 mm) spine and a 5 in hidden tang for a wa-style handle. Add 1/8 in for clean-up and you need 2 1/8 in. That is just over 2 in, so it rounds up to the next listed width: 2 1/2 × 1/4 in flat bar. A deba up to 1 7/8 in tall would fit 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 pointed. The handle hangs off the spine, and the edge drops below it at the heel. KraftyDesign starts Japanese patterns at 3/32 in, but a deba is far thicker than that, so the preset uses 1/4 in.

Wikipedia puts most debas at 5 to 7 mm, and retail 165 mm debas are often thicker. Chef Knives To Go, a knife retailer, lists a 150 mm single-bevel deba at 6 mm at the heel and a 165 mm one at 7 mm. Two other shops list 165 mm debas at about 8 mm. So 1/4 in is at the thin end for a full-size 165 mm deba and about right for a 150 mm one. For a heavier deba, set a thicker spine. The next thickness up that the calculator lists as common for 1084 is 3/8 in.

The calculator starts on 1084, and 1095, 52100, AEB-L and MagnaCut give the same 2 1/2 × 1/4 in bar. 14C28N isn't commonly listed in 1/4 in, and the calculator flags it. Check what your supplier stocks.

The calculator starts on Forged for this one, and it sizes a hidden tang narrower and thinner than the blade, the way you would draw it down for a wa handle. Forged, it takes just under 5 in of bar per blade, clean-up included. That is about 14 oz of bar for a blade that finishes near 9 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. If you start thicker and forge down, set "Forged thickness" to "One size up". On this preset that starts you at 5/16 in, which the calculator flags as uncommon for 1084. It only applies in forged mode. 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.

Stock removal is where a deba wastes steel. It takes the whole 6 1/2 in blade and 5 in tang plus clean-up: 11 3/4 in of bar per blade. That is about 33 oz of bar (about 2 lb) for a blade that finishes around 12 oz, so nearly two thirds of the bar you paid for goes to the grinder. A 12 in bar gives one blade, and so does an 18 in bar. The 24, 36 and 48 in bars give two, three and four. The 12, 24, 36 and 48 in bars all come out at the same cost per blade.

Three shops list their 165 mm debas at about 9 to 10 1/2 oz with the handle, so the calculator's steel-only estimates may run heavy. Weigh your first one, and if it comes out lighter, adjust the fill factors under Calibration.

What a deba is for

A deba is a Japanese knife for breaking down whole fish. Wikipedia says it is designed to behead and fillet fish. Korin, a Japanese knife shop in New York, says fish markets and restaurants that work with whole fish use it. Wikipedia says the thick blade, often with a more obtuse angle at the heel, cuts off the head, and the rest of the blade rides against the bones to separate the fillet. It is not a cleaver, though. Korin says it is not meant for large bones or for slamming down like a cleaver, and Japanese Chefs Knife (JCK), an online Japanese knife retailer, warns that sideways force on big bones can chip or crack the blade. JCK matches size to fish: 150 mm for fish of 15 to 20 cm, 165 mm for 20 to 40 cm and 180 mm for fish over 50 cm. The ko-deba is the small one, about 100 to 120 mm, and JCK says it is common in coastal areas of Japan for small fish. The mioroshi deba is longer and slimmer. JCK calls it a hybrid of the deba and the yanagiba, the long, thin sashimi slicer, and Sakai Ichimonji, a knife shop in Osaka, says it is lighter but can chip on tough materials. The deba comes from Sakai, in Osaka Prefecture. The prefecture says Sakai's smiths started with tobacco knives and were making deba knives early in the Edo period (1603 to 1868). The Japanese Wikipedia article gives the earliest record as the Sakai Kagami, a book on Sakai published in 1684. It calls the deba a knife for preparing fish, and the article says it seems to have been a known Sakai product by then.

Most debas are single bevel, and that changes how you grind one. Wikipedia says they usually come right-handed, with one bevel on the edge and a hollow back, the urasuki, on premium blades. Ichimonji says the hollow keeps the back of the blade away from the pressure of the food being cut, and calls it one of the key reasons to have a single-edged knife at all. When you sharpen, the back lies flat on the stone and only the flat rim around the hollow touches. Ichimonji calls that flattening ura-oshi. In a BladeForums thread on single-bevel Japanese knives, one poster puts the urasuki about 1/8 to 1/4 in from the edge and 2/3 to 3/4 of the way up the back, on a 24 to 36 in radius. In another thread, one poster starts it as a groove down the middle of the back on a big wheel or a radiused platen, then works outward. Another reply warns not to go so deep that you notch the blade. Traditional debas are also not one steel. Hocho-Knife, a knife seller that lists addresses in Florida and Japan, calls this a kasumi build: high-carbon steel at the edge and back, soft iron for the rest, which makes sharpening easier. A knife of one high-carbon steel is a honyaki, which it says chips more easily and is hard to sharpen. A deba made from one bar of 1084 is a single-steel knife. If you laminate your own, expect it to move. One BladeForums poster laminated a chisel-ground knife with a 6 in edge from two steels, one of them low-carbon horseshoe stock, and found the tip had moved 1/2 in during normalizing. A reply says it will likely warp, being a bimetallic strip with different expansion rates. The steels differ too. The Japanese debas cited on this page are white (shirogami) or blue (aogami) steel, and neither is on BladeStock's list. In a BladeForums thread comparing white steel with 1095, one poster says the alloy differences are so small that at the same hardness and geometry, users couldn't tell which was which. Not every deba is single bevel, either. Ichimonji lists the yo-deba, a thick double-edged deba with a Western-style handle.

How the deba got its name is unconfirmed, so take it as lore rather than history. The Japanese Wikipedia article quotes the Sakai Kagami as saying the smith who made it had a mouth with protruding teeth (deba, 出歯), so people called it the deba knife. The article reads that as the spelling later changing to 出刃, with the character for blade. Ichimonji calls a buck-toothed Sakai smith one prevailing theory. The Japanese article says a book from 1734, the Honchō Seji Danki, tells a similar story, but gives no citation for that. None of these sources names the smith.

Stock for a deba

In a BladeForums thread on deba dimensions, one maker worked out a 0.250 in spine tapering to 0.130 in with a 3/4 in wide bevel, then settled on 5.3 mm (0.210 in) of MagnaCut. Another poster in that thread puts most 18 cm debas at around 5 mm tapering to about 3 mm, and calls 7 mm really thick even for large ones. At the slim end, a single-bevel AEB-L mioroshi deba with an urasuki, listed for sale on BladeForums, was 4.3 mm thick above the heel on a 220 mm blade.

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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