Honyaki question

[TaJ]

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!

[jaybett]

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

[CrisAnderson27]

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!

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

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

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.

[Messy Jesse]

That was a great read! Thank you.

[KimBronnum]

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

[TaJ]

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.

[CrisAnderson27]

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.

[TaJ]

That'd be great.

[Matus]

Very interesting thread to read. Looking forward to pictures

[CrisAnderson27]

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