Making The Trap Spring Knife

The trap spring knife is rugged, versatile, and simple. The only tools you will need are a grinder, files, a forge or a hot burning torch, and the trap spring. 

The first step is to take your trap spring ( which should be very large; a size #3 or bigger), heat it up and flatten it. 

Next you will need to anneal your metal to make grinding easier. To do this you heat it up to a dull red and let it cool on its own in a bed of ashes or in the dirt. After it is completely cool it is in its softest state. 

Now grind your shape and add the primary bevel. This could be done by using a belt sander, or hammer the edge as thin as possible, then file the rest of the way. before you harden it, the edge should be fairly thin. It will be much harder to work after hardening and tempering.

To make the metal hard enough to hold an edge, you will harden it.

With a pair of tongs grip your knife profile very firmly. Now heat it up with your torch or set it in your forge. Get it to a glowing red, and then dunk it quickly in a pot of oil. (One way to tell if it is ready to be quenched is to touch a magnet to it. if it is not magnetic you may quench it) You must quench in oil. It does not have to be a special kind, but water will crack the metal. Quenching makes the metal very hard.

To make sure your knife is hard, run a new file over the edge. If the file slides over it, it has been hardened successfully, but if the file catches it was not done right and you need to try again. Hardening makes the metal as hard and brittle as it can be. Be very careful and do not drop it in this state. 

Now you will need to remove some of that hardness to make it workable. Put the knife in your oven set at 400 degrees for two hours. It is now tempered.

With your grinder or files do the final grindings and sharpen it. One last tip: wire brush your knife instead of polishing it  You can add decorations to the handle like rawhide or paracord, or you can leave it how it is.

Good luck making knives, and happy New Year.

A finished knife and a profile, from one trap spring

--Caleb