Japanese web info list

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Stainless steel rust pitting, deep, like 1/3 mm, this after thinning

 

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Successful straightening of honyaki yanagiba with tagane

Before

After

 

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Hammer marks, they go away quickly with 400 grit stone. The shinogi crisped up again afterwards. Scratch marks from the anvil. Paper on the anvil can prevent that but damps the blow slightly, could be a good thing sometimes. I didn't use paper

 

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Tools used, and tip picture. The lines perpendicular to the edge are scratch marks from me dragging the carbide chisel tip to locate where to hit far enough from the edge, not cracks

The principle is that the dents move the metal away from the shape of the dent. The second principle is that these blows cumulatively curl metal. This means the ura can get deeper or more shallow, digonal bends or twists can be made or reduced or acccomdated by hammering everywhere else instead. The third principle is a bit mathy of physics - ey, but blows add up to make a resultant. Which is to say, if I hammer in two perpendicular lines like a right angle, the result is similar to the effect of hammering a diagonal line, in effect in curling the knife. Single bevel design detail to note is the spine can protrude on the ura more than the edge, so the edge must be bent over more. Or the spine hammered on the ura side to reduce protrusion.

The diagonal marks form almost like a V -- those are to form a curve in the metal there or to remove a curve, depending on whether I hammer on front or back, or with the point of the V facing spine or edge.

There are a couple ways to bend to get edge contact on the ura. I can either deepen the ura (hammer the front evenly where I need edge contact), thicken the edge (hammer close to the edge but risk cracking and chipping more), simple bending (hammer perpendicular to edge).

Oh! You can also hammer the ura and front to add and subtract ura curve to different places. So you can deepen the ura close to the edge, and make is shallow close to the middle. Custom ura

 

[ethompson]

Very impressive

 

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After setting the ura again and wide bevel sharpening, low spot at heel (one picture is cut off a bit)

 

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Polished with 320 grit cerax fingerstones, low spot near heel. I tagane straightened after this too. Scratch at tip on ura from carbide chisel, not a crack

Had to hammer the ura at and near the spine near the tip area, parallel to the spine. The spine and edge each have their own bends. When I bend the whole blade, or the edge, sometimes the spine protrudes too far and prevents the edge from laying straight. Cheaper single bevel yanagi sometimes have this problem, and it can be a stylistic, or compromise choice too. One goal is an evenly deep ura that tapers smoothly heel to tip, so that's made first as a goal, since bends away from the ura are still more sharpenable than no ura or badly shaped hollow.

A smaller carbide chisel is useful for hammering the ura perpendicular to the edge to get out bends towards the steel side.

Making both the spine and edge straight is the most difficult way to construct a single bevel. Given a straight edge, the straighter the spine is thinner the effective cross section is, so there will be less steering and wedging, and a better in hand feel, and less edge bending as the knife wears down. The edge doesn't bend necessarily due to relieved stresses in this case but I think because of the edge-spine relationship is for the ura.

This honyaki also had a hairline crack that revealed itself and disappeared after 30 minutes of thinning afterwards. I didn't even hammer it at that spot too.

I asked around and Murray Carter and epic edge offered to honyaki tagane straightening, so if I failed to move the knife I intended on sending it to them.

This took me 6 hours though of hammering and checking . . . .

Probably the most happy I've been about being able to do something, but I never want to do this again, it's super laborious, and honyaki just wanna break themselves. I think it's good to start a little softer in hammer blows, to see how the steel responds. It's important to make sure the steel is supported underneath the hammer hit. If there's a sharp bending induced, like hitting an arch at the top, cracks and breaks seem to occur more that way in my experience on hard steel.

Even if visually I can't see a difference immediately, I can feel it in hand when I pinch over the area. I can tell a rough and smooth surface obviously, but the distances difference for that is really small, so I'm both surprised and thankful I'm able to check that way

Steel feels -- if you've wanted to know is Sakai honyaki like in steel. Peak sharpness feels actually a little less than the most excellent clad knives, but better than most carbon knives. This has happened with the 6 Sakai honyaki I've sharpened takohiki, yanagiba, gyuto, gyuto, usuba, yanagiba, and 2 ishido honyaki I've owned, the watanabe honyaki. Only the takagi honyaki got as sharp as the very best I've tried.

Toughness in the steel at the edge seems better than most clad knives, though macro-toughness seems lower, so I think that's an explanation of honyaki edge retention.

In hand feel doesn't seem all to different to me, I prefer clad knives with their more dramatic tapers and shaping.

 

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Crack on front on wide bevel, perpendicular to edge

Crack doesn't extend to ura

Swarf from 400 grit

 

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Cheapest US carbide chisel hammer I've seen by kraft tool for $47.50. 8oz /15mm / 3/8".

https://dev.krafttool.com/RO3122-5-8C?gQT=1

I'd recommend a small tile chisel if you're going to hammer the ura perpendicular to the edge, around 8mm or so. Those are cheap like $15.

For advanced single bevel ura work, once I get the edge straight, I have to get the spine side straight too. I put the knife backside on a flat plate, and rock the ura to see where the high spots are. I hammer the ura near the spine to bring those down.

The edge in a yanagiba is curved and forms a plane. I try to hammer the ura close to the spine down to be in line with the same plane as the edge. Assuming the edge is straight. Might have to bend a little too. But that's a check to do, is the spine getting in the way of the edge.

 

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For the honyaki yanagiba, what if wasn't able to straighten the knife, set ura edge contact, untwist, and uncurl the spine on the ura -- then what? I contacted some shops and makers to see what choice there is, if someone else purchased a honyaki yanagiba and it was bent, or if I didn't take all this time to find resources and tools, practice, test, and learn it.

Japanese Knife Imports: No, possible and experience doing so but time consuming, expensive due to labor, risk of blade breaking. Mentioned tagane.

Epicurian edge: Yes, $50-100 estimate but can be more. Mentioned of risk of breaking, no guarantee of perfection but if it doesn't crack it will be straighter.

Bernal Cutlery: No, high risk of breaking. I've seen them use tagane in the videos though

Strata: No, tricky and risky, good luck though

Carbon knife Co: No, JKI might be able to help

Murray Carter: Yes, unstated but reasonable cost, no eta

Korin: Yes, but no additional warning of risk, but I mentioned I knew it was risky

Shihan: Possible yes but sometime when he's not busy. He said he does tagane for every blade

Hitachiya: No

Yoshihiro Hayate in LA: Yes, $60, said it will be improved but can't do too much, would take 2-3 business days (given the previous yanagiba honyaki repair saga sent to them this year IDK)

Aftamestokyo: no, good luck though

Given this, I'd go to Epicurian Edge, Murray Carter, or Shihan for honyaki yanagiba straightening, with Murray having the most experience.

 

[simona]

I recently started using a knife I bought some time ago, and in trying to learn more about the smith, came across;

https://www.katanatogi.com/

 

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Ebuchi honyaki

Finally found an example of one, I knew he made them, and thicker knives in general but never seen one

江渕作

 

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More straightening progress

"Straight" -- what is it for a knife? Edge, geometry, and spine. But for almost all knives they geometry isn't symmetrical . . . So I need an ideal for what works well for that kind of grind or use.

In this case, single bevels, the geometry is, shinogi, ura, blade face.

For an ura, the basic requirements are there must be a hollow and edge contact. Ideally, the edge should be straight, but the knife is usable slighly bent. It's ok to have a straight edge and wonky spine -- knife is still usable and sharpenable. If the spine is far to the left of the edge, it make the knife thicker with regard to steeeing, and there will be more wedging and the knife won't feel as nimble. Except near the handle I guess, that makes it feel more workhorsey or strong.

If the tip is bent toward the iron or front side, doing wide bevel sharpening will wear down the tip faster, and the tip will feel fatter, and the tip work won't feel as precise or predictable compared to straight. I have to lift up to deburr the ura, or press the edge lightly. This is workable, and better than the opposite.

If the tip is bent toward the steel or back side, I need to press down harder to deburr, which prevents fine stropping at light pressure. It will dig into the stone, too, unless I sharpen it sickle style with a rounded stone or the edge of the stone. Eventually the bent part should wear down, but in practice it only does if I excessively sharpen it, forming burrs and reprofiling it. Which is to say, whichever side the steel bends too, sharpening that side will sharpen the edge and form a burr and wear down fhe profile faster. This applies to a bend within the edge profile too, in the middle of the knife. This is a what confributes to wavy edge profiles.

A straight knife will sharpen predictably, and gives me the most control over geometry and profile.

Now to the more relevatory stuff. A while ago I straightened a biggerson for @kpham and discovered removing twists using a chisel hammer in an X pattern, / on one side of the blade and \ on the other side, (looks like an X if the blade was see through).

I've only seen / or diagonal marks on on side and always in that orientation, with the knife side toward my face, edge pointing down, tip to the right. When I would use that, the knife would curl, and I'd have to hammer the spine or edge back to straight and repeat that process in a cumbersome manner.

With one of the X patterns:

(/ On front , \ on back ), it lets me twist the blade on a single bevel, to make the edge contact more (pushing it toward ura), and the spine contact less (pull away from ura).

How this looks is, a / chisel mark on the front of the knife like how the tip of a knife goes diagonally up. Flip the knife over, don't move the the chisel, and hammer again. This will produce the \ mark (hand has the same chisel hammer orientation, but flipping the knife flips the orientation of the mark on the knife ). The two hammer marks keep the center of the knife centered -- it doesn't bend overall but instead twists.

I have a flat plate to check my work visually and by feel. I rock the knife, do I feel a simple bend? Is the spine gouging the plate slightly more? -- means I need to twist the spine away a bit, if there's no edge contact, so I can get edge contact too.

Low spot at the spine side of the ura has bothered me for a while. Many knives that seemed to have "full" spine ura contact were actually bent. Once I straightened the edge, it no longer had that pretty ideal.

Hammering in the opposite X pattern lets me get spine contact for the ura throughout, both at tip and other places in the knife (\ on front of knife kinda parallel with spine profile, and / on back kinda parallel to edge but more like 45 degrees for both instead of parallel)

The edge result is a really planar ura that sharpens super responsively and pleasantly, and a front geometry that also feels well shaped and responsibive.

When checking on the flat plates, it's easy to rock the knife and forget there's a curve or bend, and instead accidentally only see the edge is straight in particular sections but not as a whole . . . My flat plate is too short

Rocking the blade back and forth to check for overall angle of ura planes too -- usually the knives rock a little and there are multiple planes to the knife will lie "flat" on. The two twisting hammer patterns lets me unify the planes.

Clad single bevel knives are easy to crack! Thinner steel, can't hit as hard, unless softer steel or finer grain. Honyaki crack more from the thermal stresses having nowhere else to go from the quench.

This honyaki has fine grain structure, and I accidentally hammered near the edge, denting it like a stamp, and it didn't crack and it sharpened out, behaving a lot like Ashi ginga white steel.

In the picture, I sharpened the ura until I could feel a consistent burr, but there's still some visual inconsistency I might troubleshoot later. The hammer marks sharpened out already on 400 on front

If you want practice, folded aluminum foil is pretty good to see how twists and bending works, paper too.

 

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How failure and cracks look like, clad knife, softer hagane than the honyaki, dents more, and iron dents more than soft steel on honyaki

 

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Shapton 320 pro / kuromaku is like a harder splash and go cerax, still muddy and fast though. I like it better than the rockstar 320 which was harder but slower

 

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Hisamoto Mini Gyuto production process diorama. Each knife is around 11cm overall length.

Width: Approximately 63.5 cm
Depth: Approximately 34 cm
Height: Approximately 5 cm

Someone buy plz

https://page.auctions.yahoo.co.jp/jp/auction/j1166075495

 

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FSK boron nitride and diamond vitrified hand file

 

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I wanted to learn more about which knives crack under chisel hammer blows, and I think the heat treat matters the most. I was wondering if it was technique, depth of the chisel mark, force applied, pressure as opposed to force (how sharp the chisel was). Of course, don't hammer hard right near the edge.

This yanagiba didn't crack under super heavy tagane chisel hammer blows. I did crack it at the heel on a separate occasion though, with the chisel hammer there . . . So thickness of the area matters. If there's any kind of arch, hammering at the top of the arch leads to the most cracking. Supporting the knife under the hammer blow or close to it helps reduce cracking. This yanagiba seemed to only plastically deform, I couldn't see cracks. I've read on the Japanese web that hammering in the iron side can crack the knife, yet I've also read shigefusa interviews say hammering the steel side is risky too . . . Idk. Maybe a bend radius has something to do with it. The previous knife I cracked untwisting it, I think had a more brittle or coarse heat treat. It felt glassier in stones, white 2, by the agasaya shinkai shop in Tokyo.

This yanagiba below I thought had great steel, responsive and crisp, not coarse, pleasant to sharpen, so happy to see that corresponds with bulk material properties. The knife did bend too, or flatten out some, so I imagine a regular hammer for straightening could work well for this knife too