I use files to make knives.
First of all, you need GOOD files.
Many files today, especially those coming from China, are just case hardened iron. Not good at all. The surface is hard, but the metal itself is worth crap.
Good files like Nicholson are made of W1 or W2 steel.
Price is usually indicative. If you get them used, try them on a grinder, grinding the side of the tip down at least 0.05" (1 mm ) and watch the sparks. You may find various references on the internet about spark testing steel. It's not an accurate evaluation method, but can reliably tell between iron and high carbon steel.
Files come in the hardened status. If you want to make a knife by stock removal, using hand files, you need to anneal them. It's mandatory.
I strongly recommend that you anneal them anyway. Files are very hard. If you drop it while grinding, or hit it badly while forging, you can break it.
I forge my knives, but anneal the file beforehand nontheless.
Removing the teeth it's up to you. I leave them for the handle on some forged knives.
To anneal, you need a way to bring the file uniformly at non-magnetic and let it cool down VEEEERY slowly.
How can you achieve such a feat? Well, forget your kitchen fires.
First, they ain't hot enough, second, your mom / wife would get mad at you. Since it's useless anyway, it's not worth it.
You need a forge. WAIT! It doesn't necessarily have to be a huge coal-eating smoke-spitting thing. I started with a micro forge that I still find quite useful for heat treating, and used it in my apartment. It's small, clean, safe and very, very cheap.
You need:
1 soft fire brick (try on glass working catalogs or refractory catalogs).
1 screwdriver, flat, 12" long (at least) or 1 wood gouge, flat, 12" cm long, 1" wide, that you don't mind spoiling.
1 wood rasp or bastard file, half round, 12" long.
10' of iron wire
2 MAPP gas torches.
Use the gouge or screwdriver to slowly drill a hole in the middle of the brick, down its length. Rotate the gouge or screwdriver and work lightly and slowly.
Getting at it with a vengeance will just risk you break it.
Once the hole is there, enlarge it. Leave at least 1/2" of thickness on the sides, and 1" top and bottom. Make an oval cavity, higher than it's wide. Use the half round file to smooth the walls, and you can paint the inside with Satanite or equivalent to make it smoother and avoid flying particles of ceramic, and increment the refractory properties of the brick. Make 2 holes large enough to let the MAPP burner nozzle to pass through. Make them so that they are at a tangent with the cavity, and at an equal distance bewteen them and the forge openings. Hot gases will swirl inside getting a more even heat rather than just blowing straight in.
Make thin indents along the brick and wrap wire around it (not accros the openings, obviously) to make it stronger. With use it will crack. Don't worry, it's normal. The wire will keep everything nicely together.
You may want to have a refractory tablet or another brick to rest the micro-forge upon, as it can get pretty hot on the outside, anyway.
Here you are.
With that, you can heat treat about 1 foot of stock length.
More than enough for most small to medium sized knives.
Light the forge by lighting the MAPP burners and inserting them in the forge. I used clamps to hold them in place by clamping the hose they are attached to to the table. You must devise a way to secure the burners in place.
Put the cans in a container filled with water, or else they will freeze and the pressure will drop.
The water doesn't need to be warm.
Wait till the inside of the forge gets hot, then slowly warm the file with the hot gases exiting the mouth of the forge.
This is to avoid putting a piece of tempered, fragile steel at room temperature in the little inferno you have in the forge.
Heat it till it's at orange heat. Best thing, periodically and frequently check the steel with a magnet: when the magnet doesn't stick, it's ready. Let it soak heat a minute or so more, then slowly turn down the gas, and leave just enough flame to keep the burner lit.
Let the forge cool down with the file in it. The slower the cooling process, the better.
When the forge is no more glowing, or just glowing barely, turn down the burners, extract them and let everything cool down to room temp.
Don't hurry things.
Now the file is annealed and ready for working. In such a forge you can anneal simultaneously 2 or even 3 files. The bigger mass will make the cooling down process slower and better.
