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Make a Karambit - Part 5: Hardening and Tempering

In this part of the tutorial we treat the steel in a way that makes it very useful and durable as a knife. It needs to be hard, yet not too hard because that means it can shatter or crack. So, we harden it then we soften it back up a bit. This two step process is called hardening and tempering.

 

We start out by heating the knife up to about 1500 degrees fahrenheit. This is the curie temperature of steel and it is the right temperature to harden it. We can tell it is up to temperature in two way. First it will turn a bright red color, and secondly a magnet will no longer stick to it.

It is red hot

This picture shows it heated just about perfectly. We are only concerned with the blade section. And we have to be real careful about the point. Don't put the point directly in the heat because it can quickly overheat to yellow or white hot. Let the heat transmit from the center of the blade out to the point.

I have a little backyard forge for this but you can use a plumbers torch for this work. I have a tutorial showing how to use a torch for this right here.

 

Quench in oil

Once you have it up to the right temperature and a magnet no longer sticks to it you quench it in oil just like this.

This locks the hardness in. Be careful, it can be dangerous and you can use most types of oil including motor oil, used motor oil or even vegetable oil.

Clean the scale

Next we have to temper it. And we do this by heating it to around 450 degrees fahrenheit. And we can judge this by the color of the steel as it is heated. So once the knife has cooled use some emory paper on it to clean all the scale off and the knife is clean.

 

The knife is clean

It is cleaned and ready to be tempered.

 

temper in heat

So, put it back in the fire but supported a couple of inches away so it is not directly in the coals. Rotate it regularly and flip it over regularly.

Watch it carefully and be sure the tip is not too close to the fire because it can overheat quickly.

It will turn a wheat color. That is perfect. When most of the blade is wheat it is tempered and ready to be quenched.

 

Wheat color

Here is the wheat color of the blade. it looks great. And we just have to worry about the blade. It isn't important for the handle to be wheat. If you overheat the blade it can quickly turn to a plum color. This softens it up even further. A little bit of plum is ok. But if there is a lot of plum you should start over, re-harden the knife then re-temper it again.

NextLet's Continue with the tutorial and finish the knife

 


 

Atlas forgeThe Atlas Knife Forge - This is a wonderful little gas forge for knife making. I also have pics of one sent in by a web visitor right here: The Atlas Mini Forge. Thinking about knife making and looking for a forge to do the job? This is it!

 

 

StingMake Sting from the Hobbit - Fun tutorial and I show you step-by-step how to make this famous sword from The Hobbit and The Lord of the Rings.

 

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