Hot folding damascus is one of the quintessential parts of the process, and it’s always a bit fraught.
The object is to take a bar of steel at welding temperature, weaken/cut it on one side until it’ll fold easily and cleanly, then you fold it, tap it back into alignment with a hammer, flux it up and pop it into the forge to re-heat. After that, you weld it and draw it out into a bar, then repeat the process some number of times to give 2x, 4x, 8x, 16x, 32x, etc. layers in the composite billet. Japanese swords typically have 12 – 14 folds because more completely obliterates the grain in the metal, and less makes the grain too obvious.
Usually, the person making the blade will declare that they want to do a hot fold, and everyone gets ready. That means that there is a student or two standing by with a sledgehammer or a large forging hammer. When the smith places the billet on the anvil, they hold a cutter tool (a wedge on a long handle that resembles an axe or woodworkers’ maul) and the student takes a couple whacks until it’s cut enough that the metal can be folded down the side of the anvil. Then, everything gets lined up, fluxed, and it goes back into the heat.
Obviously, that’s not really a one person process unless the person is very stubborn and practiced. Farting around too long on the anvil can result in the metal oxidizing and then it won’t weld, and hitting the cutting tool off-center can result in a yellow hot billet of steel shooting around the room, and attendant excitement.
So, I thought I’d solve the problem for myself.
That’s a press die I made that carries a cutting blade I hand-ground (it took hours!) from a piece of 1/2″ thick S-7 shock-resistant tool steel.
You can see the area where the edge was forced into a hot billet, and there’s not much damage. A little bit, sure, but I can touch it up in a year or so if it gets decroded. Everything in a smith’s shop that repeatedly comes into contact with steel at welding temperature (including the smith!) oxidizes faster, so wear on contact points is inevitable.
Yesterday’s experiment consisted of taking a piece of 2″ wire rope, 6″ long, then heating it and consolidating it into a square-ish bar, then drawing and flattening the bar into a billet about 8″ long, 1.5″ wide, and 1/2″ thick. That was cut with the tool above, most of the way through, folded in half on the cut line and welded then re-drawn into a billet of about the same size, and the process repeated. Cable loses its texture pretty fast if you stretch it a lot so I thought 2 folds would maintain the inner structure. We shall see! The billet is in the annealing bin and today it’ll be cool enough to bandsaw in half so I can check for flaws in the consolidation.