I take a old coil spring from a car and turn in in to a Viking seax and you can to

Step 1: Gather the Steel

I use old Honda suspension coil spring and cut a pice off with my angle grinder

Step 2: Forge the Steel Flat

Take the pice of spring heat it up to a hot orange color and use a hammer and anvil to straighten then flatten the steel in to a useable billet for the knife

Step 3: Forge the Blade

Use the hammer to move the steel in to the shape you like I went for a Viking seax style blade

Step 4: Forge the Handle

Using the horn of your anvil share the handle to what you think will work best then let the knife cool to air temperature

Step 5: Grinding the Knife

Using a belt sander grind the handle flat and Grind bevels on either side until you have a thin edge

Step 6: Heat Treat

Heat up the knife to a orange color and quench in oil until it is cool to touch then temper the knife at 450 degrees for 2 hrs and let cool and your knife is ready for a handle