that comes with the territory. You learn to live with it."
When he finally obtains enough layers in his billet, Duncan stops welding and lets the billet cool. He cuts a piece from the billet roughly the size of the knife he wants to make, and then he reheats it in the forge. Once the metal is malleable, he uses a 25-pound trip hammer, along with an old-fashioned anvil and hammer, to pound the billet into the type of knife blade he wants to make.
In a separate workshop wait a fascinating array of belt sanders and grinders. For the next several hours, Duncan will sit in a veritable shower of white-hot sparks as these machines shape the blank into a serviceable blade.
"For most of my work, I use a grinding belt that's two inches wide and 72 inches long," Duncan explained. "I start with a 36-grit belt, which is really coarse, and gradually step down to a 400-grit finish, which is very fine."
When he finishes grinding, Duncan holds a nearly-completed knife blade with a bright, mirror finish. Now, it's time to heat-treat the blade, which he does with an acetylene torch. He reheats the blade to above 1,800 degrees, and then quenches the cutting edge in Canola oil. This heat-treating process hardens the edge, but leaves the rest of the blade softer so it will flex.
If you look at one of his knives that's heat treated, you'll notice a distinct line where the steel changes color. That's called the Harmon line, where the steel goes from hard to soft.
"Unfortunately, the edge is too hard at that point," Duncan said. "I have to draw it back by heating it up to a lower temperature--say 325-450 degrees, depending on the type of steel in the blade--for one to two hours. The amount of time also depends on the type of steel. I repeat this process two or three times."
This process is generically called tempering. More accurately, it is called stress-relieving. That brings the hardness down to 58 on the Rockwell Scale, where before it was 61 or 62 or higher. It shrinks the grain size of the steel and makes it very fine. That makes the knife a lot tougher. A knife that is only heat treated is very brittle.
After tempering, Duncan regrinds the blade with a 400-grit belt to remove hard scale that builds up from the heat-treating process.
After removing the hard scale, he attaches the guard and handle material to the knife. He fashions handles from a myriad of materials, including burly maple, walnut, antler and horn.
Now we're down to the trim work. Duncan grinds the handle and guard to the desired shape, and then finishes them by hand-sanding. Sometimes he uses a buffing machine to give the guard and pommel a mirror finish.
He then soaks the blade in ferric chloride, a highly corrosive acid, for 30 minutes or more. The acid eats away at the high-carbon steel but does little to the high-nickel steel. This exposes the different patterns in the blade, but at first, it turns the blade jet black. To neutralize the acid, he washes it off with water and dishwashing soap. Then, with 1,000-grit sandpaper, he sands the blade by hand. This highlights and brings out the blade's delicate, signature Damascine pattern.
The knife is now finished. All that's left is to sharpen it and make a sheath for it. The product is a knife for the ages.