In this part of the tutorial we harden and temper the knife blade.

The purchased blank of Damascus steel is annealled. This means it is soft and workable by tools. Which is a good thing. Otherwise we wouldn't have been able to cut and file it. But this is no good as a functioning knife. It needs to be strengthened by hardening and tempering.

This will make the knife durable and strong. It will keep a sharp edge. Yet it will still have some resiliency so it doesn't shatter or crack.

Hardening and Tempering the Blade

Our first step is to heat up the blade of the knife. We don't have to worry much about the handle. We focus on the blade.

We are going to heat it up to about 1500 fahrenheit. It will be glowing red hot. And at this temperature the crystalline structure of the steel will have change.

But how do we know when it is at the right temperature?

We check it with a magnet. The steel is magnetic. When it gets to the temperature we need it will lose its magnetism.

So, as it is getting red hot check it with a magnet.

Once a magnet no longer sticks to it, put it back in the fire for another 30 seconds.

Then quickly and efficiently plunge it into the quench. It needs to drop by about 500 degrees in less than a second. This will give us a good hardening.

About the quenching liquid.

This will depend on the type of steel or steels in your knife.
Generally with damascus water is used. It will help with the quick dropping of temperature.

It is also a bit more risky. The quick drop in temperature may crack the knife.

I am using used motor oil that I have pre warmed by plunging a hot iron into it. This technique potentially doesn't give us as good a quench but it does decrease the risk of cracking. We may get a knife that is not as hardened as it could be. It is a trade off.

The knife is now hardened. You can check it by gently running a file over it. You will hear the difference. It will be like sliding a file over glass. The file won't bite the steel it will glide over it.

Next we will temper the knife. In it's current state it is very hard. But it is also brittle. If you were to drop it onto a hard surface it could possibly shatter. That is not a good characteristic of a knife.

What we want is to find a balance where it is strong and tough so it will be durable and hold a good edge. Yet we want it to be soft enough to take use without cracking or shattering.

We find this balance of characteristics by now tempering the blade which is heating it to a bit of softness.

Start by cleaning off the knife with some emory paper. As we are heating it we will watch the changing colors of the steel.

Now we are going to slowly heat the blade to about 500 fahrenheit.

Do this slowly. Place the knife a distance from the fire like you see here.

And notice how I have the spine of the knife toward the fire. This is a good technique and it helps prevent the thin edge of the blade from heating too quickly.

How do we know when we have achieved the right temperature? We can't check it with a magnet this time. That would be about 1500 F.

But we can monitor the color changes as it heats up.

We bring it up to wheat color. This knife is just about there. You can see it starting to turn wheat. A little bit more.

Quench it once it gets to wheat color.

Okay, the steel has been treated. It is hardened and tempered. Let's continue on with the making of the knife.

How to make a simple yet effective Blacksmithing Forge (The lawn mower forge -lawnmower not needed). I show you how to make a forge. This includes the concepts of how a forge works and how to make it. This is the forge that I use in all these tutorials and videos.

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