Recommendation? Temper on blades.

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Gearjammer95

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Dec 15, 2018
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I apologize if this is the wrong place to post this, I’m going to fill out my profile and change my name.
I’m new like many, and I wanted to ask what those more knowledgeable about forging think about the temper on these blanks.
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It’s only my second attempt and my friend’s first. I don’t know the exact content of the steel, just that it is hardenable and will skate a file. It’s not ideal but it’s what I have access to right now.
I don’t know if I tempered it too much or not. It still seems hard and rings like an Estwing hammer.
Any and all advice welcome.
 
Welcome. It would help if you told us how you hardened it.

Many new makers confuse the words harden and temper. hardening makes the soft steel hard, but brittle. tempering softens the steel a bit and removes the brittleness … so you can use the knife. Most folks temper too low. Unless you are deliberately shooting for a very high hardness with a known kitchen knife steel, tempering at 300 to 350F will leave the blade far too hard and likely to break.

As a rule, with mystery steels, temper for one hour at 400F, cool to room temp ( just run cool tap water over it) and put back in the oven for a second hour. This should make a usable blade.
 
I heated to non magnetic, held it for a bit longer and quenched in water. Then I put it in my garage toaster oven at 400 for about an hour.
 
That HT should work (assuming the steel is hardenable), but a second temper is part of the process. If you don't do it, there can be some edge chipping with some steels. With your mystery steel, I would do another temper at 400F.

How did you know the steel was hardenable? What did it come from?
 
I have access to machinery and equipment pieces, I heated a rod and quenched it in water and couldn’t get a Nicholson file to cut it, I tempered another piece to purple and it was soft enough that it would cut.
 
The problem with machinery pieces is you have no idea of the alloy type. While it may harden, it may make a poor blade. Most won't work with a backyard HT.

For example - Take a big drill bit. You can forge it out to a blade shape, and harden it as you did ...but the HSS will not properly harden. It may skate a file, but it also may not hold and edge, or may snap easily. The steel in a drill bit needs a HT oven and temperatures at 2000F and higher to properly harden.

Water quenching is a very bad idea, BTW.
 
I suppose if you're willing to invest more time you can put a rough finish on them and see how they do? Put an edge on them and chop a bunch of stuff to see how it holds up
 
I would do your heat treat on a sample of that steel and then snap it off and look at the grain structure. It’s easyer to fix it now the. After you snap the blade off becaus of huge grain.

I found this out the hard way awhile ago when I forged a sword from a plow spring. Looked very nice and heat treatedti the hardness I wanted. But it took a slight bow during the quench. As I was trying to straighten it snapped. And the grain was absolutely huge. I did some tests on it and could at that time not get the grain down to what I would I consider an acceptable size. So it’s worth testing a sample befor you put a bunch of time into mistery steel.

Also you would be surprised how low the carbon content can be and still skate a file. I have skated a file with steel with .40 carbon. So that is not a good test on weather you have a good knife steel.
 
JT brings up a good point … skating a file doesn't tell you a whole lot. Coarse pearlite will skate a file. Heat a 1X.125" bar of standard welding metal from Home Depot. It has between .18 and .26% carbon ( usually, its 1018 or A36). Quench it in water - It will snap easily if bent, and it will skate a file.
 
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