Hardening a double edge knife

B . Buxton

B . Buxton

Joined
Jul 8, 2001
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I'm working on a forged double edged knife, similar to a dagger but 1 1/2" wide and 8" long. Is there any way I can edge quench the cutting edges and leave the middle soft without a lot of trouble, and if I quench and harden the whole blade is there anyway of drawing out the middle to soften without taking the hardness out of the cutting edges.
Is it possible to bring to quenching heat and quick quench both cutting edges and get equal hardness.:confused:

Thanks
Bill :D
 
I remember a few years ago Wayne Goddard wrote an article for Blade Mag. about his "weiner roasting method" Basically he used a barbecue spit type system to rotate the double edge blade in the heat source and quenched the whole blade when the edges were even colored and nonmagnetic. This left the center soft unless you heat too long and bring the center to critical temp also before quenching. It was a hand crank instead of an electic spit.
 
Bill,
I was gonna say that there isn't any way to quench one edge and then the other, but I got called away to dinner, and I was thinking,

If in stead of moving your blade in the bath to cool it, you add a couple of jets, (whirl pool quench) the moving quench bath pulls the heat from the blade. now roll the the heated blade edge point edge through the bath. If the blade is thin enough, it just might work.

years ago when I was an aprentice, I asked how a particular tool was made and was told that I had to heat w-1 to critical and quench it in oil. This causes only the outside of the steel to harden, while the inside stays soft. That way a fine edge could be ground on an impact resistant piece of steel.( this of course does not work with oil hardend steels)

I did it accidentaly to a dagger. I was trying to heat up an 11 inch to critical with a torch (actualy 4 plumbing torches) I got the edges and point to temp, but the spine didn't quite make it. after quenching, boy was I suprised, I don't know if I could do it on purpose though

The guys here have a method that uses clay, but hopefully one of them can explain it. I'll have to play around with it before I realy understand it. I have drawn out the center of a blade with a torch. The color to watch for is dark blue, go slow and quench often to keep the heat under control.

but if you don't want to do alot of engineering, and you don't feel lucky you should get someone to explain how to use clay.
 
This struck a memory...

There was an interesting article in the march '96 issue of Blade Magazine called "How to heat treat and get an attractive temper line." basically, the technique uses furnace repair cement (that black goop in a tub) instead of clay.

If it works, you would get hard edges, and a soft spine. Depends on the steel you're using, but a hamon would be a bonus.

Food for thought.
 
Bruce & Eric,

What do you think about this, if I harden the whole blade then sandwich about 1/4 to 3/8" of each cutting edge in between 2 pieces of 1/4" plate steel and then heat the middle with a torch. The plates should absorb the heat before it gets to my draw temp while the middle softens up ????? What do you think?

Thanks

Bill
 
I think the furnuce cement (black stuff) on the center with about 1/4" of edge showing. Heat the whole blade fast in a hot fire and quench in warm oil. Temper as usual. I bet you will get those hamon lines too. Good idea Centaur!
 
Centaur & Bruce

I believe you fellows are right, that sounds like the easiest and probably the best way. Thanks I'll let you know how it turns out.

Bill
 
Bill,
I have a book called the "Art of Blacksmithing"
by A.W. Bealer in it he refers to a red-hot bar, then says "When tempering two-edge swords, the hot iron bar is placed in contact with the center ridge or blood gutter of the blade." I've no experience, it just sounds plausible to me, maybe work on your dagger. Just thought I'd pass it along.
Regards, Greg
 
Thanks Greg that is something to think about, I've got 2 I need to finish first, then I'll try something????? ;)

Bill
 
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