Thread: Tempering homemade knife blades

Originally Posted by Fuzzie

It appears I've opened a larger can of worms than I originally intended. If the current blades don't seem to work well I don't think I'll be in a position to rework the heat treatment at high temps.

Since the intent was a quickie bench knife, if I start again with an old hacksaw blade will I need to heat treat? Can I just cut and shape on a grinder?

Of course you can but if you over heat it you may destroy its temper but y udon;t have anything to loose from trying.

As mentioned heat to non magnetic red. This is a good way to rough test the heat without trying to judge by colour for the inexperienced keep heating and testing to see if a magnet on a stick will cling to the metal.

when heating a thin blade especially you should heat from the back of the spine not laying on the side as this can cause /the blade to warp on quench.

When quenching as mentioned above don't stir put it into the oil and completely submerge in a cutting or a stabbing action depending on the shape depth of quench tank. If you don't completely submerge the blade you will create a differential hardening and a fault which will pose the risk of snapping.

You can temper in your kitchen oven at 2 cycles of 1hr at 200C for most things as a stress relief.
I tend to just heat from the part I want softer and let the colours run. I.e. Up to peacock on the soft part and run to dark straw where I want to keep hard.

Just to finish off this thread, I eventually decided to make up the smaller blade as it had more chance of having reached hardening temp. My first attempt at a handle failed as I attempted to use two steel nails as rivets, these did not mushroom over, bending instead and splitting the handle.

I made a second attempt and used some brass screws for the rivets this time. I probably cut them too short, but at least the peening of the ends didn't split the handle this time.

I filled the rest of the blade kerf with $3 epoxy from the reject shop. It's the first time I've tried to use epoxy for something like this. I expected it to setup much quicker, like builders bog, but it stayed quite runny for some time. I initially left the filled knife on the bench for a little bit and turned around to find the epoxy had all leaked out onto the bench! I did it again and taped it up to set the second time.

The blade seems sharp at the moment, I don't know how long it will last. I don't think I'll be bothering to make a second one.

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