# Honyaki question



## TaJ (Jan 8, 2014)

I think i understand what a Honyaki blade is about - a single piece of forged steel (as opposed to a clad steel blade with softer outer steel and a hard core). 

I have read that Honyaki blades have a better edge holding ability than non Honyaki blades *of the same steel*. Also i have read that they are more prone to chipping than non Honyaki blades.

If the same steel and a corresponding heat treatment would result in the same hardness of a.) the whole Honyaki blade (apart from the upper part of the blade in case of Mizu-Honyaki) and b.) the core (and thus the edge) of a non-Honyaki blade, why should the edges be different in edge holding ability and being prone to chipping?

Tom.


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## JBroida (Jan 8, 2014)

the heat treatments are not the same... not can they be... clad knives are heat treated differently from honyaki knives


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## TB_London (Jan 9, 2014)

The treatment of the steel during the knifemaking process is also slightly different e.g heating to forge welding temperatures to stick the layers together, and the potential for carbon migration from the core to the cladding could also be considered.


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## TaJ (Jan 9, 2014)

I said 'same steel' but did not mean to say the same heat treatment. I meant a heat treatment that would shoot for (and result) in the *same hardness* of the edge. Is that possible and if it is, would the edges still differ in edge holding ability and being prone to chipping or would that be the same?

Or is it the case that using the same steel, one can achieve a *higher hardness* in Honyaki blades and thus have the different characteristics? For instance due to the different heat treatment or because of this:

TB_London


> The treatment of the steel during the knifemaking process is also slightly different e.g heating to forge welding temperatures to stick the layers together, and the potential for carbon migration from the core to the cladding could also be considered.


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## Crothcipt (Jan 9, 2014)

Different construction of both knives gives both "better" character. Usually the Honyaki is a lot thinner, and doesn't have a different steel for a core. The softer steel absorbs any shock that may cause some chipping with a honyaki. You can have both at the same hardness but the construction itself will be a big difference you see. Most honyaki's have the soft part of the blade on the spine vs. the softer steel in the middle. This needing a totally different heat treatments. Also higher hardness usually means more "chippyness"


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## TaJ (Jan 10, 2014)

So, it boils down to the steel on the edge being similarly brittle when it's the same steel at the same hardness. Differences may be found in the structure of the steel itself, due to the different process used to produce the blade (heat treatment and such). Also the kind of blade (Honyaki or clad steel) is plaing a role in how the force is applied to the edge and thus how it's affecting it. Does this sound about right or do i miss something important?


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## Crothcipt (Jan 10, 2014)

There is a lot more to it than that.


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## TaJ (Jan 12, 2014)

Crothcipt said:


> There is a lot more to it than that.



Of course there is a lot more on the topic of blade steel than 3 sentences. More like 3 shelfes full of books. 

My question was simple, i thought so at least. I have read every thread i could find with 'Honyaki' in it in this forum (apart from every BST thread). I could find something supporting what my guess is now and some opposing opinions.
:dontknow:

If you know what's more to it, concerning my question, please share


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## CrisAnderson27 (Jan 14, 2014)

TaJ said:


> I think i understand what a Honyaki blade is about - a single piece of forged steel (as opposed to a clad steel blade with softer outer steel and a hard core).
> 
> I have read that Honyaki blades have a better edge holding ability than non Honyaki blades *of the same steel*. Also i have read that they are more prone to chipping than non Honyaki blades.
> 
> ...



The cladding would have zero effect on the chippiness or lack thereof of the same edge steel tempered to the same hardness. Things that WILL have an effect on chippiness with those two things controlled, are all in the heat treat. How long did it soak at quench temp before actually quenching? How high was the quench temp? What was the quench medium (water, brine, fast quench oil, food prep oils, motor oil? The options are endless here). What temperature was the quench medium at the time of quench? How long was the blade submerged? Was the quench interrupted? All of these things have a huge impact, and changing one only changes everything. The main goal is to get the blade hard of course, but controlling the carbides is right up there...and that is all in how a blade is heat treated. Large, irregularly spread carbides are BAD. They chip out very easily. Small, uniformly spread carbides are very, very good, and can increase edge retention and overall sharpness a hundredfold. Again, these things have nothing to do with the tempered hardness.

On the cladding 'supporting' the edge...unless the core steel is thinner than the thickness behind the edge, this is a falsehood. Also, the whole concept of clad blades for performance is based in the making of swords (as is differential hardening, or 'mizu honyaki). The whole 'shock absorption' thing doesn't apply to a kitchen knife, or even to a cleaver for that matter. Imagine it this way...a 240mm (9.5") long piece of obsidian (very, VERY brittle) would chop on a cutting board forever without snapping. Now slam a 28" long piece down with the kind of force necessary to dismember a human being wearing even leather armor...and you get the picture. In all honesty, cladding is mostly used to bring the price down, by using cheaper low carbon steel for the body of the blade. This of course excludes stainless clad blades, which are clad for an entirely different purpose. 

I'm not sure if that helps at all, but I think it gives you a better overall picture of the processes...and can possibly help you to figure out a few other directions to research in search of your answers.


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## seward (Jan 14, 2014)

Nicely said.


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## TaJ (Jan 15, 2014)

Very interesting writeup CrisAnderson27.

So, given the same steel and the same resulting hardness, the goal with both kind of blades is to achieve a good structure of he steel with small uniformly spread carbides to get the desired attributes of the edge. So let's assume the knife makers succeed getting there with both kinds of blades, then there would be no relevant difference in brittleness/chippiness between Honyaki- and clad steel knife edges. Differences would be there if one would not achieve that, meaning you could have a brittle Honyaki- or a brittle clad steel blade edge. I hope i got that right.
Your description/exapmles on the cladding are eye-opening as well.

Cheers!


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## jaybett (Jan 15, 2014)

Honyaki is so confusing. There has been other threads that have followed this line of thinking. Then there have been the threads about the difference between a mono steel knife such as the Suisin Inox Honyaki and a traditional Honyaki knife. 

What I wonder is what qualities does a honyaki knife have that make it desirable, besides the cool hamon line? I've read that they take a keen edge, edge retention is very good, but they can be difficult to sharpen. Some members have commented that a Honyaki can feel glass like on the stones. 

So what kind of user, would need or want a honyaki knife?

Jay


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## CrisAnderson27 (Jan 15, 2014)

TaJ said:


> Very interesting writeup CrisAnderson27.
> 
> So, given the same steel and the same resulting hardness, the goal with both kind of blades is to achieve a good structure of he steel with small uniformly spread carbides to get the desired attributes of the edge. So let's assume the knife makers succeed getting there with both kinds of blades, then there would be no relevant difference in brittleness/chippiness between Honyaki- and clad steel knife edges. Differences would be there if one would not achieve that, meaning you could have a brittle Honyaki- or a brittle clad steel blade edge. I hope i got that right.
> Your description/exapmles on the cladding are eye-opening as well.
> ...



Pretty much, yes. But, there are other differences as well, that come into play for other reasons. More on that below.



jaybett said:


> Honyaki is so confusing. There has been other threads that have followed this line of thinking. Then there have been the threads about the difference between a mono steel knife such as the Suisin Inox Honyaki and a traditional Honyaki knife.
> 
> What I wonder is what qualities does a honyaki knife have that make it desirable, besides the cool hamon line? I've read that they take a keen edge, edge retention is very good, but they can be difficult to sharpen. Some members have commented that a Honyaki can feel glass like on the stones.
> 
> ...



The first thing I'd like to mention, is all honyaki's are monosteel, its part of the definition. Monosteel means one homogenous piece of steel was used to make it, rather than being clad, or folded/welded like Damascus.

Now, to comment on the rest of your post, and tie in the above quote as well. A honyaki in and of itself...is nothing special. The edge is left harder than most blades, which (all things being equal) will allow greater sharpness and edge retention. However, the whole 'all things being equal' is the catch. That 'cool hamon line' you mentioned, is the mark of an extreme level of quality. It takes a stupid amount of effort, and a fair amount of skill to pull it off on a kitchen knife thin blade. See, a through hardened blade sees a relatively uniform amount of stress in hardening. It may warp a bit, but if its quenched properly it pretty much stays true while being quenched. Anyone with a piece of steel, a way to heat it, and something to quench it in...can pull off a through hardened blade. Most amateur bladesmiths start with through hardened blades for this very reason. 

Differentially hardening (honyaki) however, is something else entirely.

Imagine a blade heated to about 1500°F. Its not uniform in its thermal mass, since you've added clay to the spin in some random pattern (believe me, the pattern does NOT help here). The blade also tapers from the heel to the tip in thickness and width, and a bit from spine to edge...adding a few other changes in thermal mass, along differing planes. Now...take said knife, and quench it in a medium which will bring the unclayed steel to around 900°F in about 1 second or so. At this point, the thinner exposed steel is freaking out, trapped in a very brittle state, while the thicker clayed steel is cooling along at a much slower, relaxed rate. What's happening right now is the edge steel is trying to rip itself free of the spine steel, and the pattern and tapers are throwing everything else out of whack while its at it. It's absolutely amazing the kind of warpage a thin blade can twist itself into while this process is progressing. If you don't know what you're doing here, you're going to have a failure rate of over 80% (at minimum) with this thin a blade. It takes a cut above in knowledge and experience to pull this kind of thing off with any meaningful level of success. That cool hamon line is the mark of a smith who knows the steel he's working with inside and out, and if he knows that, he's going to know how to bring the best performance out in that steel as well. Now don't get me wrong!! Non honyaki type blades can be made to perform JUST AS WELL in the hands of an experienced smith! We have dozens of examples in the custom makers on this site. But, 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.

And really when you break it down to its most simple form, that's all it comes down to.


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## Messy Jesse (Jan 15, 2014)

That was a great read! Thank you.


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## KimBronnum (Jan 16, 2014)

That was a very good explanation, Cris A. Very informative reading.


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## TaJ (Jan 16, 2014)

Cris, thank you for explaining. Not only my initial question about the edge characteristics has been answered, you've provided very interesting information on knife making, putting things into perspective for me.

:goodpost:


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## CrisAnderson27 (Jan 16, 2014)

No thanks necessary guys, I'm glad to help. 

I'm also going to run some pictures past the mods and see if its ok to post them. They illustrate EXACTLY what I mean when I talk about failed honyaki blades and why making them is such a trial.


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## TaJ (Jan 16, 2014)

That'd be great.


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## Matus (Jan 17, 2014)

Very interesting thread to read. Looking forward to pictures


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## CrisAnderson27 (Jan 17, 2014)

The mods have approved my pictures. I'll be posting them when I get home shortly.


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## panda (Jan 17, 2014)

i'm still not sure what the real world benefit of honyaki in a kitchen knife is, if any.


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## CrisAnderson27 (Jan 17, 2014)

So here we are. These pictures are examples of just one pitfall which might befall an inexperienced, impatient, otherwise unprepared, or just plain unlucky smith who attempts to differentially harden a kitchen type knife. Even worse, this steel is 1075, which is incredibly forgiving due to its rather moderate carbon content, and general lack of complex alloying agents. 






Overall blade.





The heel. If you look at the crack to the far right, you can see what I meant by the harder...quickly cooling edge steel trying to rip itself away from the softer, more slowly cooling steel of the spine.





More of the edge.





And the tip.

What happened with this blade, is the clay layout allowed extremely rapid cooling in the precise areas where the cracks propagated. Imagine clay lines stretching down and insulating between the cracks, channeling the quenchant towards the steel in those areas. In addition, it was a bit (perhaps 100°-200°F) too hot when going into the salt water, and was held in perhaps a second too long. All three of these are very small errors, which are very easy to make. 

This brings up another point. American made honyaki blades, from custom makers, are almost invariably heat treated in a PID controlled oven, allowing thoroughly precise temperature control, and timed soaks at that temperature. When you know what you're doing, this helps tremendously with the success rate, along with ENSURING that each blade reaches the utmost potential of the steel its made from. The few Japanese smiths capable of pulling off honyaki blades (I've read there are only five?), do so without the benefit of temperature control. Everything is by eye (color), and feel (the blade just feels _different_...I don't know how else to describe it...). That is how I taught myself to do it initially, and believe me...was I ever grateful to be able to eventually build my oven. I would never, EVER want to go back to doing it that way, and have nothing but respect for those Japanese smiths who continue to do so. 

I think when you're purchasing a Japanese honyaki blade, that's a large part of what you're paying for. Not only the properties in the knife itself, but the skill that allows a master of his craft to find success in a task where most other practitioners find only failure.


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## CrisAnderson27 (Jan 17, 2014)

panda said:


> i'm still not sure what the real world benefit of honyaki in a kitchen knife is, if any.



I think the real benefit is more personal. As a non chef type person, I've cut the same foods with both types (of equal quality), one after the other...and a differentially hardened blade just feels like it cuts differently. The edge seems keener, and seems to last longer. This could be perception of course, and without some real form of testing the actual results can't be proven. I will say that since honyaki blades are generally tempered to a greater hardness, the benefits I noticed are likely real...if something less than measurable. In addition, as I mentioned...a person making a honyaki blade is virtually guaranteed to know what he's doing. They aren't something you make in batches...and as such, the greater level of attention could very easily add something to the finished product. Similar to a factory built Ford Mustang, versus a Rousch or Shelby version.

The same thing can be said of most if not all through hardened custom knives sold on this forum as well though.

So in the end, I'm sticking with personal benefits when compared with other, high quality customs lol...and more measurable benefits if its compared with a more generic knife of course.


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## Keith Sinclair (Jan 17, 2014)

panda said:


> i'm still not sure what the real world benefit of honyaki in a kitchen knife is, if any.



Panda I used a Takagi Honyaki in production kitchen,admit I bought it because it was a good deal on JWW had some superficial flaws & cheap handle that I changed.Best Lobster blade ever for me.It keeps a sharp edge longer than any steel I have used in a kitchen knife,Carbon or Stainless.Once it is trained like any other carbon blade sharpening is not a problem at all.


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## TaJ (Jan 17, 2014)

Cool pictures. You can picture the huge strain in the steel while quenching the blade nonuniform.

As for real life benefits of a Honyaki blade, i don't see really important ones. One attribute that may be a benefit for certain knives is a blade being made out of hard steel entirely may have less flex as compared to a clad steel blade. This might enable a thinner blade while still being quite stiff.

Other than that, i'd bet a nice Ardbeg that it would be impossible to identify a Honyaki blade against an otherwise identical clad blade (shape, geometry, steel, hardness, similar weight) in a cutting blind test (test flexing not allowed).
:running:


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## bkultra (Jan 17, 2014)

CrisAnderson27 said:


> I think when you're purchasing a Japanese honyaki blade, that's a large part of what you're paying for. Not only the properties in the knife itself, but the skill that allows a master of his craft to find success in a task where most other practitioners find only failure.





CrisAnderson27 said:


> In addition, as I mentioned...a person making a honyaki blade is virtually guaranteed to know what he's doing. They aren't something you make in batches...and as such, the greater level of attention could very easily add something to the finished product.




This is the exact reason I bought my honyaki knife. Your posts have reminded me just how much I value what it took to craft mine, thank you for that.


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## CrisAnderson27 (Jan 17, 2014)

TaJ said:


> Cool pictures. You can picture the huge strain in the steel while quenching the blade nonuniform.
> 
> As for real life benefits of a Honyaki blade, i don't see really important ones. One attribute that may be a benefit for certain knives is a blade being made out of hard steel entirely may have less flex as compared to a clad steel blade. This might enable a thinner blade while still being quite stiff.
> 
> ...



Actually, stiffness is more a factor of geometry...rather than hardness. For example, a through hardened western sword blade with a fuller, will be much stiffer than a through hardened western sword blade without one, at the same hardness. Another example...stainless steel, mild steel, and hardened tool steel rods all have a similar stiffness (resistance to bending) rating, although the hardened steel will snap at a much earlier limit, of course.

Stiffness and flexibility are also both highly subjective, and often mistaken for each other. Do you mean resistance to flexing (stiffness)? Or ability to return to true after being bent (flexibility)? Many people use them interchangeably, but they are very different things. A perfectly flat, thin (1-2mm) spring tempered (about 500°F) piece of hardened steel will bend 90° and return to true easily. That same piece of steel, ground into a diamond (think double edged sword) geometry, will 'flex' much less, thus being 'stiffer'. Cut grooves (fullers) in that diamond geometry, and the stiffness increases even more. Note that you have changed nothing about the hardness of the steel. Just its shape.

On the honyaki thing. I do feel the need to say (again) that a through hardened blade will often be tempered (hardness reduced to increase toughness) at a higher temperature than a honyaki blade. This absolutely changes its physical properties, including edge holding, and sharpness. The reason for this is that a very thin, 2" wide blade at 65HRC is a very brittle, and thus easy thing to snap. 61-63HRC is more of a reasonable limit for that kind of thing. A honyaki blade can be left at 65HRC due to the support of the soft spine, without fear of actually breaking the knife in two accidentally. Just something to keep in mind.


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## jaybett (Jan 17, 2014)

panda said:


> i'm still not sure what the real world benefit of honyaki in a kitchen knife is, if any.



This is the point I was trying to make with my post. What are the real world benefits of a Honyaki knife?

At the prices being charged for Honayaki knives, it would be hard to imagine that it would come down to personal preference. Knifes such as Kato or Heji require a certain skill level to maintain and use. I'd think that Honyaki would be similar. From what I've heard, ability to take and edge and retention are key factors. It would be nice to hear from member that have picked up a Honyaki knife their impressions.


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## TaJ (Jan 17, 2014)

I meant the resistance to flexing kind of 'stiffness'. So, my assumption that it may be stiffer was wrong, thanks for clearing that up. I should have looked that up before assuming wildly. And ya, geometry plays a big role. Why else would we use differently shaped girders (which only Bender is able to bend  ).

Yes, i understand that for actual knifes the resulting hardness often differs for Honyaki blades and clad steel blades. So, maybe one could say, for Honyaki blades it's almost a defining attribute to have a high hardness and thus (almost) every Honyaki edge is as hard as only the hardest non-Honyaki edges, which are outnumbered by less hard non-Honyaki edges. That may be the root cause of the often heard statements that lead me to ask the questions of my first post to begin with.


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## panda (Jan 18, 2014)

ok that i can understand, 'feel' is the one big reason to prefer carbon over stainless so makes sense.


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## Crothcipt (Jan 20, 2014)

panda said:


> i'm still not sure what the real world benefit of honyaki in a kitchen knife is, if any.


I pretty much get the same reply when someone is referring my knives to the line beaters.

It has been said many times here on the forum, after about 500$ mark the differences is very slight. I still want one.


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## sharptools (Aug 9, 2015)

CrisAnderson27 said:


> So here we are. These pictures are examples of just one pitfall which might befall an inexperienced, impatient, otherwise unprepared, or just plain unlucky smith who attempts to differentially harden a kitchen type knife. Even worse, this steel is 1075, which is incredibly forgiving due to its rather moderate carbon content, and general lack of complex alloying agents.
> 
> 
> 
> ...



Bringing back an old thread. Which are the 5 smiths? This sounds pretty insane.


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## CrisAnderson27 (Aug 9, 2015)

sharptools said:


> Bringing back an old thread. Which are the 5 smiths? This sounds pretty insane.



I have no clue...it's just something I'd read...and being that many years ago, I can't even recall where I'd read it, lol. Jon Brioda could probably fill you in a bit more accurately than I can in that regard.


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## JBroida (Aug 9, 2015)

what am i being asked about?


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## CrisAnderson27 (Aug 9, 2015)

JBroida said:


> what am i being asked about?



Back when I'd posted this, I'd read that only a handful of Japanese smiths were capable of doing honyaki blades. I thought you might verify the truth of that? The gentleman above also asked which smiths those were.


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## JBroida (Aug 9, 2015)

there are a small number, and even less who do them well. I'm not sure i can share all of their names publicly though.


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## CrisAnderson27 (Aug 9, 2015)

JBroida said:


> there are a small number, and even less who do them well. I'm not sure i can share all of their names publicly though.



Thanks . That's pretty much all I was able to say...and my comment was only based on what I'd read. Good to have someone who actually knows verify it.


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## sharptools (Aug 10, 2015)

Thanks for the answers!


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