Thread: Meat cleaver restoration

Originally Posted by roughkype

I hope I'm not blundering into some awful punch line, but have to ask: what's a hamon?

Hamon 刃文 is a Japanese word for temper line. The literal translation is something like 'Cutting edge writing'.
If carbon steel is heat treated, it can happen that one part cools much faster than the other. If this happens, the quickly cooling part hardens completely, and the other part simply cools down and remains 'soft'.

Where the hard part and soft part meet, there will be a visible 'flaw' in the metallic structure.


Among blade enthusiasts, this is considered a desirable aesthetic. With swords and knives, there are functional advantages as well. Not only will it define the mechanical properties of the sword, but also how prone the edge is to chip, how any damage would spread, etc. For kitchen knives it is purely aesthetic. With cheap blades and swords, this is sometimes faked by etching it on. A real hamon is visible even if you'd polish the steel, though it is usually highlighted by careful manual polishing and soft acids.

The effect is controlled by coating a blade with a thin layer of clay before heat treating. The clay protects the blade from scale forming. Then, the part that has to stay soft is coated with a thicker layer of clay. Where the 2 meet, the hamon will form. Based on how the line between the 2 is shaped, different hamon patterns can emerge, and there is actually a large amount of identifiable patterns.

I have always thought of the hamon of a sword, knife, or razor the inner beauty of the steel.

Wow. Another reason for amazement at what clever monkeys we've become.

And it's a relief to know a hamon is nothing like a daugwhay.

Ok a quick update.
I clayed the blade, and performed the heat treatment when I finally had my forging setup working.

Here is the blade with the clay coating:


Here is the blade after heat treatment:


And here is the blade after grinding and polishing.
It is extremely difficult to capture it properly, with the blade surface not being flat.
Also I am not yet happy with how the polishing has turned out. It is serviceable, but I am not yet satisfied. Up to 1K, the hand polishing was ok. After that I tried a BBW and a coticule, but those are really not great for Japanese style polishing. After that I tried poliching compounds on wood, which was somewhat better, but that destroyed the hazy finish I was trying for.
I dipped it in light etchant to highlight the hamon.

I also cut several fingers in the process of polishing and etching


Now I still gotta figure out how to cut the handle, and also how to get the polishing done right.

You can get a good result going up to 2k with wetndri & WD40. Then switch to some Hazuya stone to polish the hamon area . No real need to use Jizuya as it is mono steel. If you have an uchiko ball you could use the powder on paper with a little oil to polish the same area.
Repeated light acid etching & subsequent polishing can yield a pleasant enough effect too.

btw . Lookin' good

Nice! And by the way, any plans you have to take that blade to Japan....leave it at home. With the hamon, you'd never be allowed to bring it into the country. I mean, just in case this becomes a knife you have to use everyday...

Really? You can't bring blades with a Hamon into Japan?
I would think that noone would mistake this with a real Japanese blade.

This is the first time I did something like this, and I was not sure how detailed the shape of the blade would trail the clay line.
That is why I kept it simple. As you can see, the way the actual hamon matches the clay line in 1 smooth line is uncanny.
Now I just need to get my hands on more carbon steel...