This thread is a must read.
Pierre, you've taught me boat loads about HT, and your post really rounded out Marko's initial one. Combined (with Jon's comments, of course), we have a very good summary of how intricate and individual ht can be. Basically, what it seems to boil down to is: there are fantastic "mixes" or "cocktails" that are used. If you want more wear resistance, or sharpness, or whathaveyou, it's a good idea to use a knife or maker that/who is known for the qualities you desire.
One thing to note to someone just starting to learn about this stuff
As Devin's post alluded to, there is a ton of bad info out there regarding heat treat. The process and results have been hyped, romanticized, theorized, BS'ed, and lied about probably since its discovery. There is of course a ton of great info out there as well, it is important but often difficult to try to differentiate the two. There is no one foolproof or perfect approach but the more you learn and understand, the more you will be able to define your process and how you get your knives to perform to your standards. Good luck!
Great post JMJ.
For those who are interested in doing their own heat treating I recommend the following; get yourself a furnace or salt pot, a Rockwell tester, a liquid nitrogen dewar, quenching oil and maybe some quench plates. Read some books on the subject and then go out there and cut some test pieces from the same batch of steel and vary the temperature 25' at a time, test the hardness, put the heat treated samples in a vice and break them and look at them under magnification, see what you can see and then make a knife and cut with it. You will see some grain coarsening with too high a temperature and breaking them will show how tough they are. Sometimes it's not very scientific but you can learn a lot.
And last but not least, don't do anything dumb and call it the greatest heat treatment known to man. There are several things that happen to steels when you heat them up, most of them are bad.
What would be some good books? I know there is a lot of ambiguous or incorrect info out there.
yup... a microscope is key (as is polishing the steel before looking at it and breaking it to look at that too). And ask questions. Some people have figured out interesting ways to achieve results. In reality, there is no one right way, but having a good logically sound method is very important.
Steel Metallurgy for the Non-Metallurgist by John D. Verhoeven is a very good one to start with.
Originally Posted by greasedbullet
Thanks, that is now in my "read pretty darn soon" list.
Ok now i have question for your quenching gurus
I am not expert in it in any way, i just know what i like and thats about it.
But what is over hardened blade for you ??
My understanding is when i have seen some over hardened knives edge just crumbled. Chips is not uniform or rounded, Difficult to explain but it is like some kind of car glass.
On the other hand, one costumer ones came to me with not one of my knives and said my knife is over hardened should i return it ?? It chips all the time etc.
After i expected it it was clear to me that it was not the case at all ! it was just very thinly grownd and user may be used it wrong too. After i sharpened it and put bit higher angle on it all was gone and he was super happy.
Now for some people it is very hard to see what is over hardened blade and what is just super hard. Personally i love them to be as hard as possible. But still without that crumpling thing.
Chips i don't care much about.
I know some may not like knives that way but it is what it is
hehe hope you understand what i mean with my crappy English
So my question i guess is What is for you over hardened blade ? And how can we decide what is right heat-thread or wrong ?
I just wanted to thank everyone that participated in this discussion. It helped a lot and is a very good read for anyone that is interested in heat treating.
me too. i had no clue about the subject and it is very interesting.