Make a knife from a file

[Echale3]

Normalization of steel, a process very similar to annealing, is useful, especially when the metal has been forged.

For those of us who forge our blades, and I've forged hundreds of them over the last 20+ years, normalization is a key step to de-stressing the blade prior to heat treat. Often I'll normalize 2-3 times just to make sure my blades are nice and "relaxed" before I start the heat treating process.

When you hit the end of a fairly malleable steel rod (an improvised punch, say), it doesn't just shorten all along its length. The extreme end is deformed into a sort of nail-head where it meets the hammer. In the same way forging affects the outside layers more thoan the interior of the metal, and one of the main skills of a good smith is to make sure he affect s it to about the same depth everywhere, and especially on both sides.

What you bring up in the first and second sentence is a good point for a person to consider when forging a blade if you want to economize your efforts. Mash metal in one direction, and it will spread in every other direction. Different shapes of hammer faces can be used to minimize or maximize that propensity so that the 'smith controls the shaping process more accurately. A good example would be the difference in metal movement when you compare a flat or rounded hammer face striking straight down versus a straight pein hammer doing the same. All other things being equal, the flat or round faced hammer will spread the metal in every direction as it compresses the metal between the hammer face and the anvil. A straight pein, however, will minimize the spread parallel to the long axis of the hammer and maximize the spread perpendicular to the hammer blow as the metal is compressed between the hammer face and the anvil.

The effect of metal movement away from the hammer face is shown graphically in the knifemaking tutorial I wrote and linked to in a previous post, and again in the belt axe tutorial I did on the same site (link here: http://paleoplanet69529.yuku.com/top...e#.VpaNMI-cEdV

But if the blade is asymmetrical, as shown abovoe in exaggerated form, it will take a sideways curve in hardening, no matter how well it was normalized. (I can't, for some reason, get out of attaching as a thumbnail an earlier version in which the asymmetry of the single-edged blade wasn't clear enough.)

If a blade is very asymmetrical, then yes, some warpage will occur, however, with only slight asymmetry, it's negligible. Interestingly enough, after the quench, if you leave the blade a bit hot, you'll have about 10 seconds to straighten the blade before it takes a "set" and is fully hardened.

I always got a kick out of showing people a trick when I was quenching hardenable steel for demonstration purposes--I'd pull it out, still smoking, immediately put a big bend it in, wait about 20 seconds, then shatter it with a hammer.

Fore and aft distortion isn't necessarily very harmful. The traditional Japanese swordsmiths reckon on forging the blade a shade straighter than it is intended to end up, and imparting 3/8 to 1/2in. of extra curvature along its length by hardening. The best of them have a wastage rate at this point, but if successful, it may actually strengthen the cutting edge. That curvature is probably affected (though whether increased or reduced I can't work out for sure) by coating the body of the blade with clay, to slow the quench and let it remain resilient while the edge is very hard. Myth notwithstanding, that edge often doesn't come to as acute an angle as western knifemakers often use.

Japanese 'smiths water quench, and the tamagahane (the traditional steel used for knife making) they select for use out of the bloom produced by the tatara (a small Japanese style smelting furnace) is typically about 60 points carbon--equivalent to our 1060 low alloy steel. The upwards curvature is mostly caused by differential cooling rates between the edge and the spine, where the spine and a portion of the sides of the blade are coated in clay slip mixture, dried, then the blade heated to the critical temperature and water-quenched. As you mention, there is a fairly significant loss rate during that process. An interesting side effect to the clay coating during the heat treat process is the formation of a hamon, which visually delineates the transition between martensitic and pearlitic steel in the blade. Nioi are the speckles of martensite surrounded by pearlite in the transition zone. All that aside, my interest lies more in making mokume gane (literally "wood-grained metal"), which is a forge-welded, multi-layered billet of dissimilar non-ferrous metals.

[54bore]

The old farmers would just grind away with their bench grinder until it got to the shape they wanted. No fancy heat treatment just grind it til it got too warm, dunk it in a can of water, and grind away some more.

I made a knife out of a file when I was in high school and this is pretty much the method I used and it worked fine, when it came to drilling holes for the handle pins I heated the points I needed to drill and watched til it started to discolor and move, drilled the holes, set the handles and used a belt sander to through several different grits. I spent a fair amount of time on it and it turned out decent, could have been a lot nicer if I'd taken more time. And like a dumb highschool kid I traded it off somewhere along the line

[Longfellow]

One of the best steels available; after all a file is nothing more than a bunch of tiny knife edges and it CUTS STEEL.

[pworley1]

One of my former students makes some beautiful and useful knives. He makes his own Damascus for some and others he makes from files.

[oger]

My Grand Father was a Blacksmith and he used to make lots of knives using old files. They were really good knives but you didn't have much choice on what it looked like.