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Why are honyaki differentially hardened?

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MrHiggins

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My total guess is that the softer part acts as a dampener to offset the harsh vibrations from the hard steel. Does the soft cladding of san mai knives do the same thing? Am I completely off base?
 

madelinez

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I think for swords it helped with shock resistance plus maybe cutting with the hard side and blocking with the soft side? Who knows.

For kitchen knives the performance impact is probably very insignificant, it's mainly about appreciating the traditional craftsmanship and aesthetics in my opinion.
 

danemonji

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My total guess is that the softer part acts as a dampener to offset the harsh vibrations from the hard steel. Does the soft cladding of san mai knives do the same thing? Am I completely off base?
Not an expert but a softer spine adds elasticity just the way the san mai cladding does. Since we are chopping vegetables and cutting meat and not chopping wood with our knives I guess even without the differential hardening you would have a hard time cracking a blade in two.
 

RDalman

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Good point, even though you don’t seem to have a problem with your AEB-L or 1.2562 mono at 64-65 hrc. The point still stands though.
Those are also diffhardened to some extent, and it helps straightening, but sure they are much worse in that regard. I do break some blades still, although not as many as when I was waterquenching the 20c monos.
 
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Kippington

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Differential hardening was a very useful property to have in swords.
When the Haitōrei Edict banned people from carrying around swords in the 1870's, smiths who lost a lot of sword sales moved over to making very nice kitchen knives. They would sometimes add a hamon to carry over the skills and tradition, but it has little effect on a blade that short.

"...as a result of the Haitōrei, swords lost their utilitarian role, and many swordsmiths were forced to turn to the production of farming implements and kitchen cutlery to survive..."

Also, a hamon is kind of a neat way of showing that the heat-treatment was done with purpose and accuracy.
____________

Someone on Instagram DM'd me to ask what steel my honyaki was made of. When I told him it was W2, he asked me what the second steel was and whether there was a layer of nickle in between them. I was like, "Oooohhhhh, so you don't know what a honyaki is..."
I had to explain the price too... :rolleyes:

https://www.instagram.com/p/B7N1G7VnhTR
 
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danemonji

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Just as a side note I really love this KKF community. Having experts answer such questions about how the knives are forged and sharpened makes all the difference. I am really proud to be part of this family.
 

HRC_64

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ideas of toughness and straightenability go together,
both require opposite of brittleness exist in the knife
 

Kai

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Humbled by and grateful to everyone that can speak well on this subject. I am new to the forums and, with a honyaki soon arriving in the mail, have spent the last week pouring through old threads, learning anything and everything I can.

Kippington makes an excellent point above that resonates with me:

a hamon is kind of a neat way of showing that the heat-treatment was done with purpose and accuracy.
In a much older thread - "Honyaki question", very worth a read - CrisAnderson27 describes this perfectly:

if the through hardened blade is generic, or unsigned, or from an unknown maker...there's really no guarantee of anything. A hamon is an outward sign of the knowledge, experience, and care given by the blades maker in the creation of it.
I find this thinking to be, above all other rationalizations, incredibly beautiful and powerful. Magic, even. We are not swinging katana around wildly, so the functional requirement may not necessarily be there. A perfect meal can also be crafted using Ikea knives, so it's not essential we break the bank. But, we are using specific tools with focused purpose. Investing in high quality knives reflects care, commitment, intention, and, when we prepare our dishes, imbues our creations with heart and soul that cannot always be articulated technically.

Also, it look good.
 
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labor of love

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No sense in generalizations of Honyaki. It seems to me that it can represent a (Japanese) craftsmen’s highest level of work, finishing and hardening and polishing.
On paper maybe it’s as useful as a mono blade, but typical Japanese mono blade seems to be of lower finishing hardening and grind quality.
I’ve talked to western makers that more or less charge the same ball park for differential hardening and San mai (give or take $50). To them it’s just another method for making a knife.
So culturally speaking it can be very different things.
I like hard steel and I like pretty things, but if I judged purely on steel alone even then I think overwhelmingly my fave knives are usually San mai.
 

Gjackson98

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Does the different hardening have any effect on the feedback of the knife when cutting?
I really enjoy the feedback/respond when a honyaki knife touches the cutting board, the ring is phenomenal.
Is it all because the steel hardness around the edge? Or dose it have anything to do with the different hardness match up?
 

ian

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I’ve def noticed a different feel/sound in mono vs san mai. In honyaki vs san mai, I could see something similar happening since there’s usually more exposed hard steel. Of course, the way the hard and soft steel are attached is different too. #nothingusefultocontributebutcontributinganyway

Edit: Maybe this discussion indicates another explanation for the origin of differentially hardened swords. There could have been some aethetic preference for a certain timbre of battle. ;)
 
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Corradobrit1

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I don't know I'm not well versed on swords. But warikomi is a little different from san mai, very cool imo when done well. Have a friend that forges warikomi really well, we have a collab upcoming.
That why I asked. Looking at how traditional swords are made the softer cladding gets folded multiple times. Then at the appropriate moment the block is split into a V section and the piece of core steel inserted which is then forge welded in place. San Mai being a classic sandwich.
 

Corradobrit1

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I’ve def noticed a different feel/sound in mono vs san mai. In honyaki vs san mai, I could see something similar happening since there’s usually more exposed hard steel. Of course, the way the hard and soft steel are attached is different too. #nothingusefultocontributebutcontributinganyway

Edit: Maybe this discussion indicates another explanation for the origin of differentially hardened swords. There could have been some aethetic preference for a certain timbre of battle.
Depends how the san mai is made and by whom. My honyaki definitely sound and feel harder on the board. But some san mai also give me this feedback. TF Denka and Kato being two. My Konosuke FM felt less honyaki-like and I think this is because the cladding is/feels softer. The Kato certainly has a distinctive 'ting' and resonance which I really enjoy.
 
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Barmoley

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That why I asked. Looking at how traditional swords are made the softer cladding gets folded multiple times. Then at the appropriate moment the block is split into a V section and the piece of core steel inserted which is then forge welded in place. San Mai being a classic sandwich.
There are many ways that "traditional" swords were made. During different periods, different provinces and even different smiths. They were experimenting a lot and many different techniques were used. Some examples, there are many more.


 

Corradobrit1

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I'm just going by the one or two examples of katana I saw being made in YT vids. As the saying goes there's more than one way to skin a rabbit.......
 

Barmoley

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Right. Just saying, you can't generalize since like you said skinning rabbits can be done multiple ways. In general;) swords and kitchen knives are so different in purpose that drawing similarities from one to another seems like a good idea on the surface, but should not be done. Like was mentioned before many sword smiths became knife and tool makers and ofcourse they took their techniques and knowledge to the new activity, but what makes sense for a sword most of the time doesn't for a kitchen knife.
 
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