Got a challenge for ya....

C

creightonfcb

Joined
Nov 5, 2005
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331
I am currently in a fairly austere location, and am wanting to make some knives out of scrap metal that we have laying around.

This is my first (definitely not last!) endeavor into knife making. I am aiming for survival type knives, so any suggestions in shape, thickness, and good materials to use are welcome.

For tempering I have the ability to make my own coal in a 50 gallon drum, but have no access to an oven to draw down the temper in... does anyone have any ideas on a substitute?

Thanks in advance!

Grimalkin
 
Not much to go on here.
First, where is " a fairly austere location"? Our son was recently in a part of the world which he referred to as "Summer Camp" in his emails. There was a lot of scrap metal laying around there,too.
Without knowing what is available to you as far as supplies and equipment,or what kind of scrap metal you have anything is just supposition. Here goes.
With no power equipment,a file,hacksaw, and sand paper will work. Charcoal will work to bring the blade up to non-magnetic if you can blow some air through it. It doesn't take a lot of charcoal,just a bit of air.You can quench in warm water,ATF,or used motor oil. After the quench,clean the blade off with sandpaper till it is shiny metal. Place a big chunk of plate metal on the charcoal,with the air not blowing anymore. Put the spine of the knife on the plate and watch the straw color start to climb up the side.When it has moved about 1/4 inch,pull the blade off for a ten seconds or so. Put it back on and watch the color move a little more, pull off. Keep repeating this until the straw color has moved all the way to the edge. The color going back toward the spine will be darker,ending in a light blue. Don't let the blade get any dark blue color beyond the spine area. and the straw should be the only color within 1/2 inch of the edge. Sand bright again and repeat. After about three of these temper cycles,the blade will have a workable temper.Clean it up, sand it to the final finish,sharpen it,and hack up a 2X4. See what happens. If all went well it should hold up.

This is all guess work,since there is no info to go on. (you should put some in your profile,too)
Stacy
 
Thanks Stacey!

We have plenty of plate metal and old armor from humvees and such where I am at. As for where I am, let's just say there is almost nothing but sand...:D

I think that the steel that I am working with is HRS used in the up-armoring of light vehicles. 4340 steel is most likely what it is according to my limited research.

The suggestion about the plate on top of the coals is fantastic, and seems like it will work!

Thanks again,

Grimalkin
 
I had a feeling you were at Summer Camp.Good luck,and please ask for any help we here at home can give you. Be safe.

As for the steel,well, 4340 is not meant to get hard and take an edge. It is meant to be tough and bend with extreme force.A leaf spring from a truck or car would be a better choice. If all you have is the 4340,go ahead and have some fun making knives,but they will not have good edges.I suppose there will be that factor of from what and where they were made to make up for the difference.
Stacy
 
4340 is a very nice steel , but not for knives .It's excellent for hammers and 'hawks.
 
It is good to know what the different steels are good for... now I am off to find some leaf springs! 1090 Steel, right?
 
1090 for leaf springs? Or are you talking about a good steel in general. Leaf springs can be made of all sorts of steel, but I hear allot about them being made of 5160 (another good steell). You should be fine with whatever the steel in the leaf spring is, and it should be simple enough to temper.
 
Are there any simple types of tests that I could conduct in order to tell which type of steel I have?

Thanks again!

Grimalkin
 
Simple tests will give you some guess as to the ability of the steel to get hard.To know what the steel is will take more complex testing.
A spark test is done on a grinding wheel and gives an idea of the carbon content. Heating the steel to non-magnetic and quenching in water will harden it if it has enough carbon. If the hardened steel is too hard for a file to bite into,that is good. Next put the end of the hardened bar in a vise and give it a pull. It should snap like glass. If it bends,it is low in carbon.Look at the grain in the break.This will give you an idea of the type of steel,too.Temper the remainder of the bar (at 400 in an oven or to just past straw color ) and see if it is more springy now when bent in the vise. This will let you know the tempering worked on the martensite formed in the quench.
These tests require prior experience with steel and testing. It is hard to say in words..."The spark looks bright"...without you actually having seen similar sparks.The simplest way to get a guess on the steel is to know the use of the scrap source. As said,leaf springs will usually work well.You may not know if it is 4160,5160,9260,or what,but you know that it was made to get hard and flex - both desirable traits in a knife.Metal designed to reinforce things (like armor plate) is meant to be tough,not hard and flexible - and usually is low in carbon,and high in alloy.Both of those are undesirable to you as a knifemaker.
Take care,Stacy
 
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