Thread: Tamahagane work in progress

Some time ago I was asked to build 2 Tamahagane razors, made from the nakago (tang) of old Japanese blades. I have 4 pieces to work with. This project is different from my previous tamahagane build in a couple of ways. First, this is not edge steel, but nakago. Second, because of that, I cannot retain the original heat treatment and hamon, simply because there isn't any. A nakago is never fully hardened.

This means that I need to do the heat treatment myself. these are the 4 pieces.



Initial spark testing confirmed that none of them was hardened in full. To verify that they were all good steel, I brought them all to cherry red and quenched in water. There was a bit of warp (to be expected without normalization and unknown heat / deformaiton history) and all of them sparked well afterwards.

The first one, closest to my calipers, was the worst in terms of rust and pitting. I decided to use that one as a testcase, to see how I could best work this steel, and to get my feet wet with the heat treatment. I decided to turn it into a fixed handle razor for a couple of reasons: The kanji were in a really convenient place for that, the mekugi ana (the hole) is very high in the blade, making it difficult to eliminate, and the blade has pitting. If I'd have to remove the pitting, I'd have to grind away a lot and that wouldn't look good. And as a fixed handle razor, I decided I could get away with the overall state of the blade, because I think it adds character combined with the kanji.

I ground around the makugi ana, and turned it into a nice thumbnotch. Additionally, the hole can be used for cord wrap. The blade is a quarter hollow, and fairly heavy.

Because I cut through various layers of steel with a hollow grind, I decided against a differential heat treatment. Such heat treatment would give me a hamon, which would look cool. However, because I cut through multiple different layers, and because I don't have a lot of metal to spare to grind away, I decided not to risk it, since it could warp bad. I don't have too many of those pieces to work with.

The end result is what you see below. A couple of things are to be observed:
There is no hamon. Near the edge you see a different in hardness that looks a bit hamon-like. This is simply due to the fact that my grind cuts through different layers, and the edge layer is harder than the other. It looks vaguely like a hamon, but isn't technically one. It also photographs badly. There are also the expected kitae kizu (lit. folding scars) which are welding flaws. This is perfectly in line with expectations, and what you get if you work with apprentices and sledgehammers instead of a powerhammer.

What I really love in this blade is the fact that the hada has become visible under etching. Hada is the grain pattern of the steel surface, and caused by the folding of the steel. The transitions from one layer to the other will become visible and give a nice grain structure to the surface, when when sanded smooth. You can think of this a bit like damascus steel, but with 1 type of steel only. You can find more info about hada here.
Jihada Forms

The hada is especially visible on the back side, where you can clearly see the wavy pattern of the welding lines.

Very cool looking with the kanji visible. Don't know what the kanji reads but, very cool!


Mike

That is beautiful work Bruno, some truly gifted work by you, it looks beautiful, any idea how old it is?

Originally Posted by Phrank

That is beautiful work Bruno, some truly gifted work by you, it looks beautiful, any idea how old it is?

Not at present. I have sent pictures to a koryu group where some sword experts reside. Hopefully that will turn up something.

Very cool, sir.

Intriguing project.

For those of us who know squat about working metal, would you explain "spark testing" please?

Thanks

Originally Posted by rolodave

For those of us who know squat about working metal, would you explain "spark testing" please?

Thanks

When you touch a piece of steel to a running grinder, it creates sparks.
If the steel is soft (because it has no carbon or it has not been hardened) it creates very few sparks, and none at all at low grinding speed. When the steel has hardened, it will create a shower of sparks. The amount of sparks, as well as the intensity with which they spark is related to the amount of carbon. By spark testing, I can confirm that the steel is hardenable. It also gives me an idea of the carbon percentage.

the color of the sparks and the way the sparks trace through the air, also give some information about how many, and which alloying elementing are in the steel. The latter is difficult and I am not that experienced in determining alloying elements.

Originally Posted by Bruno

the color of the sparks and the way the sparks trace through the air, also give some information about how many, and which alloying elementing are in the steel. The latter is difficult and I am not that experienced in determining alloying elements.

Chromium makes the sparks more red and suppresses the carbon staring. Manganese whitens the spark and adds to the staring.