Common nails are made of iron, (or of mild steel in this case you must anneal them when you feel they are getting harder to hammer) ; any nail, around 3 inches long, can be turned into a small knife. Old bent nails cost nothing so you can try and make different shapes at no cost. Annealing means bringing the steel to a red-heath temperature and letting it air-cool.
Step 1: WHAT YOU NEED
Step 2: Bend the Nail
To prevent it you first slightly bend the blade then hammer the inside of the curve.
2) Blow after blow you will see the blade straightening. The point of the nail gets the right shape by itself if you hammer it evenly.
3) The stake you’re hammering on had better be a bit rounded since you have to “pinch” the edge of the blade.
Step 3: Round Off the Head
5) Tuck in this edge bending it down.
Step 4: The Shank
7) After flattening it, the shank is hardened: to soften it you must bring it to red heath with a flame and let it air-cool.
8) Now you hold the shank with two pliers and twist it.
9) Some hammer blows on the twist will straighten it. Now you have a small handle with a good grip.
Step 5: Finishing
11) If you want you can hone the cutting edge and go over the rest of the knife with different grades of abrasive paper.
12) Your raw material costs nothing (old and bent nails), forging a small knife is a question of minutes: there's plenty room for experiments with different shapes and sizes. Enjoy yourself!
PS. To see more tutorials on metalwork go to my site www.pennabilli.org