Hardening a Knife

[snarble]

Hello everyone,

I was wondering, could you heat up the knife for hardening in a fire rather than a forge? If no, does anyone have a simple forge design?

Thanks.

 

[wildman695]

a decent blow torch will do it if surrounded by firebricks failing that the old fasioned hoover produced sufficient blow from the rear to work as a forge blower just connect to a long length of pipe and place under your fire, you can get sufficient heat that way.

 

[Dave Budd]

I've used a bbq with any vents opened and I've used the coal boiler at my folks house. a single soft firebrick hollowed out and a blowtorch will become a one brick forge (google it )

lots of ways of constructing simple forges suitable for heat treating or even forging. a shallow hole in teh ground with a hairdryer or bellows will do it easily too.

 

[HillBill]

I use a gas bottle cut in half, legs bolted on and a hole cut in the bottom with a steel pipe coming from it, i attach a hairdryer to this as bellows.

Better explanation here with pics (not mine but what i built mine from)

http://www.britishblades.com/forums/showthread.php?t=57990

 

[JohnC]

This is the setup I use. Like HillBill's, its a gas bottle one, I use a foot pump.

 

[snarble]

What will happen if you overheat 01 tool steel? Couldn't I just stick the steel in hot coals of a fire? Or does a fire not get hot enough?

 

[Ogri the trog]

What will happen if you overheat 01 tool steel? Couldn't I just stick the steel in hot coals of a fire? Or does a fire not get hot enough?

I think it is entirely possible to overheat O1 in a fire, but if your pumping a bellows, it shouldn't be too severe. If it does overheat, it burns the carbon out of the steel, degrading any hardness properties ( though a better informed metalurgist is bound to be along soon with a better description).
I heat treat my knives in my coal fired kitchen range!

ATB

Ogri the trog

 

[snarble]

How easy is it to overheat 01, if I keep my eye on the knife while it's heating in the fire?
In other words, how quickly will it overheat?

 

[launditch1]

If its just for hardening i wouldnt heat the 01 past a cherry red heat.Thats cherry red in the shade,or semi-darkness.

Do you have a magnet?When the steel reaches the curie point it becomes non-magnetic.When it reaches this point,quench to harden.

 

[HillBill]

Do you have a magnet?When the steel reaches the curie point it becomes non-magnetic.When it reaches this point,quench to harden.

This is how i do it also ( triple quench). Never had any problems overheating. With the method i posted above it is a matter of maybe 90 seconds or so When you can see the blade glowing well in the coals, check it. A powerful magnet from a speaker does the job nicely. Make sure the magnet is strong

 

[snarble]

Ok, thanks everyone. I'll put it in the fire coals until it becomes cherry red in the shade a strong magnet no longer sticks. Then quench it in oil.

 

[robin wood]

overheating comes in two stages, yes if you get it past bright orange into the white heat area you will see sparks and that means you are burning the carbon out but at a much lower heat, maybe around bright orange you change the crystaline structure and get big crystals which you don't want. As others have said take it only just to non magnetic and quench.

Then you need to temper it.