Hamon thread

Bruce McLeish

Bruce McLeish

Well-Known Member
This might be opening a big bag of worms, but , hey, let's get some learning going on here. K?
my understanding is that hamons are an result of differential heat treat. That is, the edge and the spine are made with different temperature.
If that is correct , then the craftsmanship comes in the making of the blade not the making of the hamon.
Now, if one wants a "showy" hamon while disregarding the blade characteristics, that's up to the maker and he should use whatever techniques he chooses to get that result.
If, however, one wants a differentially heated blade and the resulting hamon, then ( it seems to me ) that a rather stringent method must be followed.
My personal quest is to have the best blade possible, along with an outstanding looking hamon.
So, gents, start your engines.
What are your thoughts ?
 
Bruce McLeish said:
, the edge and the spine are made with different temperature.
If that is correct , then the craftsmanship comes in the making of the blade not the making of the hamon
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Thoughts??? OK, but be careful what you ask for ;) .
I'm not sure this is 100% correct. It's my understanding that the hamon line is showing where the steel transitions from martensite (hard steel) to pearlite (non-hardened steel). This happens primarily through the HT process, not the forging. Thicker steel will change temps slower than thinner steel, so I guess this could also affect the shape of the hamon.
But I think it's mainly the application of the clay, using it's insulating properties to control of the heat (either by keeping the spine cooler and making sure the edge is the only part of the blade that transforms from body-centered cubic (BCC) to face-centered cubic (FCC) structure before quenching, or using the clay to maintain the heat in the spine during the quench allowing the edge to cool sufficiently fast to harden and remain FCC after quenching while forcing the spine to cool slower, allowing the steel at the spine to transform back to BCC structure while in the quench medium) and what happens during the quench>tempering has more effect.

EDIT: I hope others with more experience and knowledge chime in.
 
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My thoughts on hamons, which probably don't account for much being I haven't made a whole lot but quite a few on hunting knives and one tanto
is when the steel is clayed and differentially heat treated it would enhance the performance of a longer blade like a sword or katana
against shock to the blade. when done to shorter blades like hunters it's more for visual appeal. and there's no denying hamons have a definate cool factor no matter the length of the blade.
As for me I just like doing them every once in a while because no two are alike, at least mine, and I find the whole process from start to finish really interesting.
 
I've picked up some W2 and 1095 that I intend to chase some hamons with. There's some very inspiring work online that I've been checking out. Look up Jan Hafinec knives (@janhafinecknives on IG) or Jarred Ball (@jball_knives on IG). They look to have spent a lot of time perfecting their techniques.
 
Bruce McLeish said:
me too. Guess that's what I get for trying to get a thread started that said " learning " instead of "opinions" or "comments from people that don't know shit about the topic ".
Silly, silly me.
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Well, speaking for me....I'm extremely busy getting ready for a show next week. I could comment, and plan to in more detail as time allows.

But if I may....the opening post seemed a bit confusing to me. You gave some of your thoughts and basically asked others for a general dissertation on hamon.

Specific questions about the process are usually more easily answered.
 
I've made a hand full of knives with a hamon, so definitely not an expert on the subject. A few of those were not what I would call a true hamon, more a wavy hardening line. To me, a true hamon should have character and activity in it.

I would guess that the majority of the blades made with a hamon were done for looks over anything else. To get a hamon with character and activity in it, I think there are some key requirements.

First is the steel. I think it's safe to say that W-2 is the king here. 1095, 1075 and 26C3 are also used for hamons.

The next items on the list are steel thickness, clay thickness and layout, austenitizing temperature and soak time and the proper quench oil. The quench oil would probably be second on the list of importance, but from there, I'm still experimenting. It seems to me, changing any of the next items, causes me to change another. If I change steel thickness or grind thickness, I have to change the clay thickness or layout to get similar results.

And if that isn't enough, then you have to figure out the etching and polishing procedure to bring the hamon out. I'm figuring on it taking years for me. Sorry for the rambling, but I thought I'd throw my thoughts out on what it takes to create a hamon and maybe spur some conversation. I definitely don't have it figured out, so if anyone has other thoughts or critiques of mine, I'm all ears.
 
Gene Kimmi said:
I've made a hand full of knives with a hamon, so definitely not an expert on the subject. A few of those were not what I would call a true hamon, more a wavy hardening line. To me, a true hamon should have character and activity in it.

I would guess that the majority of the blades made with a hamon were done for looks over anything else. To get a hamon with character and activity in it, I think there are some key requirements.

First is the steel. I think it's safe to say that W-2 is the king here. 1095, 1075 and 26C3 are also used for hamons.

The next items on the list are steel thickness, clay thickness and layout, austenitizing temperature and soak time and the proper quench oil. The quench oil would probably be second on the list of importance, but from there, I'm still experimenting. It seems to me, changing any of the next items, causes me to change another. If I change steel thickness or grind thickness, I have to change the clay thickness or layout to get similar results.

And if that isn't enough, then you have to figure out the etching and polishing procedure to bring the hamon out. I'm figuring on it taking years for me. Sorry for the rambling, but I thought I'd throw my thoughts out on what it takes to create a hamon and maybe spur some conversation. I definitely don't have it figured out, so if anyone has other thoughts or critiques of mine, I'm all ears.
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Well said Gene.

I'll repeat what I said in another thread....

I've spent a fair bit of time and dozens and dozens of blades chasing hamon and I will be sure to let the forum know when I finally do one I'm satisfied with.
 
Bruce McLeish said:
that's all i'm asking for.
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well, what is the definition of "experience"? So when does knowledge without practical application of said knowledge start to be considered experience?
Bruce McLeish said:
my understanding is that hamons are an result of differential heat treat.
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Yes, basically, the hamon line is the demarcation between hard and soft steel. In my experience, there are 2 ways of achieving this "differential hardening". As you know, to harden steel you have to first heat the steel to at least the austentizing temperature to get the phase shift from BCC (body-centered-cubic) to FCC (face centered cubic), and then once there, you have to cool the steel fast enough to prevent it from shifting back to BCC. So to get the differential hardening (and resulting hamon) you can prevent the spine from reaching the austentizing temp by applying an insulating layer of clay and heat the blade in a forge so you can make sure the edge reaches the critical temp while keeping the spine cooler.
OR You can use the insulating clay and heat the blade in a HT oven, getting the entire package up to critical temp, and then quenching. This time the insulating clay is keeping the heat in the spine, allowing time for the phase shift back to BCC to happen at the spine, but the edge stays cool and hard in the quench medium.
Over the years, I've asked a few different Master Bladesmiths who do do a lot of hamons how the different approaches can affect the hamon outcome, and have never gotten an answer, always something like "I haven't tried to compare the two, I use what works for me and what I can predict the outcome using my technique"

Bruce McLeish said:
then the craftsmanship comes in the making of the blade not the making of the hamon.
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Not sure what you mean here. Making the hamon is part of making the blade.
Are you are asking how the thickness/geometry of the knife in section affects the hamon? If so, I would guess that it does, (thicker steel retains heat longer than thinner) but I'd be surprised if anyone has studied this enough to be able to give any concrete advice.

Good luck and be sure to share what you learn elsewhere.
 
Some of the most interesting and active hamon is achieved using no clay at all, relying heavily on cross sectional geometry and precise temperature control and time.
 
Different kinds of blade hardening and perceived (desired) benefits

Fully through hardened- "100%" tempered martensite. Highest strength, good toughness. No aesthetic qualities.

Differential tempering- fully through hardened, tempered martensite, plus deeper draw tempering toward the spine. High strength edge, higher toughness spine to resist shock. No aesthetic qualities. (Unless you leave the "blue back" colors intact, not real durable)

"Thin clay" differential hardening- Used primarily (and most effectively) with shallow hardening steels to slightly adjust hardening temperature and/or quenching speed to yield a hard edge and mixed structure of martensite and pearlite toward the spine. Stronger than pearlite but tougher than martensite. The etched and polished "transition zone" can produce aesthetically appealing patterning and depth in the steel.

"Thick clay" differential hardening- Thicker clay is applied to the spine which will give a hard edge and leave a very narrow transition zone between the nearly total pearlite spine. Etched blades will show a prominent temper line.

Edge quench- fully heated blade only inserted into quenchant along the edge. Fully hard edge, soft pearlite everything else. Etched blades will show a prominent temper line.

Edge only heat treat- often done by a torch or dedicated apparatus to heat only the targeted edge area to austenitizing temp. Hard edge, soft pearlite everything else. Etched blades will show a prominent temper line.

That's all I got. Not exhaustive, and given with common definitions as they exist today.
 
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