Heat Treatment, how / why does it work?

plus the baked on oil is like a teflon coating and helps prevent rust. you guys better temper that blade after you harden it like that or it will be very brittle.
 
We're talking about a 4 dollar rip off. It won't be missed.


But if the blade gets solid red in color, what temperature is that? I'm assuming it's no where near A1 is it?
 
Colors are very subjective in general, even more so with different ambient lighting. It could have been above, below, or just right, no way to know without more info. A common term is "cherry red" for quenching temp, but I never saw a cherry that looked that color, so there's that subjectiveness again. A good test is to use a magnet, the steel will become non-magnetic right as it hits AC1, and just a little soak should allow full transformation to austenite.

If you want to go by color, the most important thing is the "decolescence"(sp). As the steel heats up and starts to transform, some of that heat is used to make the transformation, releasing less of it as light. Basically as it heats up it'll get brighter and brighter until it gets to the right point, then dim slightly (probably along the edge first) and this slightly less bright part will spread over the whole knife and then brighten up again. When it brightens again that's the exact second to quench it for best results (with simple steels).

For your other question that I missed... while there's alot of controversy around it, for an averagely skilled person you can get equally good blades from hammering or grinding. Some folks will say that the very top of the line forgers can get better results while others will say that's nonsense, but unless you're a master smith there won't be any difference worth mentioning.
 
Now, my friend heard the very basics of what happens to heat treat a knife. So he scraped off the paint, and stuck the knife in his wood stove. He heated it up till the blade was glowing red, then dunked it in Motor Oil. The blade seems a little harder, but the main thing I've noticed is that it hasn't rusted yet. Anyone have any comment on this?
Click to expand...
the blade now has oil on it.
 
So, for a poor man's heat treatment (assuming that I can get this knife hot enough), I would put it in the fire. Once it loses it's magnetic powers, I bang out what I want. I stick it back in till it loses it's magnetic powers once again.

Then I'm supposed to put it in some type of oil which is supposed to be a certain temperature?
 
Basically yes, followed by 2 tempers. 400 is good if you don't know your steel and are just guessing. Starting lower and testing, and putting it back in a little hotter and testing, until it's just right is better.
 
So I would drop it in oil that was heated to 400 degrees Fahreinheit? And then I just let it sit there till it's room temp?
 
No, you'd quench it in oil much cooler then that (unless you're marquenching, which isn't really a beginer thing), between 120-160 is good, if it's uncomfortable for your finger but doesn't burn then it's probably good. After you're done quenching and it's the temp of the oil then clean it off and put it into a toaster oven or a regular oven, let it cook in there for an hour or two and take it out, let it cool, and put it back in for another hour or two.
 
lasersailor184 - Get a couple of books on knife making and read up on forging and heat treating.If you drop a red hot blade into 400 degree oil you could be in for a very nasty fire.It takes a bit of knowledge before you start messing around with hot steel.Learning + practice = enjoyment.Lack of information + inexperience = disappointment.
 
For mystery steel and guessing then 400f. But like I mentioned, starting lower like 320f or so, and testing after each temper and raising the temp a little and testing until just right, is a much better way. Use the brass rod test to check the temper.

Bladsmth made a good point, you can learn the very basics much more easily from a book, which gives you a good foundation for asking even more questions. "$50 Knife Shop" by Wayne Goddard is probably the best book I've read for beginers, there's other good books too but that one seems to cover the very basics the best.
 
brass rod test is; after the heat treat, chop at a piece of brass rod with the knife. if it chips, more tempering, at a higher temp. probably up 25 degrees. if the edge dents or the edge curls over, you need to reharden and temper again at less heat. basically a trial and error.
for the hardness testing to make sure the blade is fully hardened. skate a file along the flat of the blade. it shouldnt cut into the steel, all it should do is take off the scale and baked on oil. cutting slightly into the steel with a file is exeptable to some especialy for a beginner.
remember this is for high carbon steels, not stainless. stainless is harder to forge and harder to heat treat for the beginer. also most stainless is an air hardening steel that doesnt get quenched in oil, water, or brine. the air is its quenchant. and there is a carbon steels that fallow the same principle it is A-1 and A-2. the a stands for air, similar to W-1 the W stands for water. and O-1 the O stands for oil.
i dont know anything about air hardening steel besides the obvious guys, so dont qoute me on anything please.
 
You're slightly off on the brass rod test though you're right about what the results show. You don't actually want to chop or cut it, you want to do more like rolling it over it. Here's something by Ed Caffrey explaining it, I want to note that in his drawing that must be an awfully wide blade, because it's really laying almost flat on the rod even though it looks like it's cutting it...

http://www.caffreyknives.net/testingart.htm

If you do 4/5 down this page there's a better picture of the brass rod test in action.

http://www.warnerknives.com/knifemaker_faq.htm
 
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