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The Newbies Arena Are you new to knife making? Here is all the help you will need. |
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#1
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Something for the VERY new at knifemaking. Heat treating and tempering.
Hello new knifemakers.
There is one topic that I see come up quite often in the Newbies forum that I think new people have trouble understanding. That is heat treating and tempering. Why do it and what is the difference between heat treating and tempering? Very often people will ask questions about how to temper a blade because they did this or that to it. But being new, they are misusing the terms and getting themselves confused. Therefore, when thay ask a question to the more experienced people the answers, although correct, are not really right because the wrong question was asked. This VERY unscientific explanation may help. I am not going to talk about the steel compoents and how they react, you can get that later in other forums here. I just want to help people understand hardening and tempering so they can ask the right questions and then understand the answers they get back. This is a little long winded so any of the other experienced people may want to let me know if something sounds out of whack. Lets pretend that steel has a hardness range from 0 to 100. 0 is the softest steel can be while in a solid state. 100 is the absolute hardest steel can get. So 0-100 range is where we have to work our knife steel, completely soft to completely hard. Well, we know that 0 is too soft for a knife because soft steel bends easily and can get scratched up easy also. 100 would be too hard for a knife because hard steel is brittle. If you bend it a little bit it breaks right off like a glass rod. Our dilema in knifemaking is to get a piece of steel that is hard, but not too hard. First we have to learn how to make steel hard. To do that, we take a piece of soft steel and get it hot. We get it hot enough to change the properties of the steel. This temperature is different for each steel but we will just say that we have to get it real hot. So we heat the steel up real hot, the steel changes it's properties (carbon steels loose their attraction to a magnet). Now it is really hot so it is also really soft. Then we take that hot steel and stick it into some oil that is cold (about 125 degrees but cold compared to the steel). The steel is shocked by the sudden cold and cools off very quickly. When it cools off this fast the properties all change again. And the steel gets really hard. The steel does not get to 100 but maybe to 80. The process that we just did is to harden the steel. Some refer to it as heat treating it but for our discussion it is hardening. Ok, so here we are with a piece of steel that is 80 in hardness. Too hard for a blade because it can break. We are going to have to do something to soften it up. The way to soften it up is to heat it up again. But we don't want it really soft so we won't heat it really hot. Just a little, to soften it up just a little. Soft enough that it will bend if forced to do so but won't break. If you were lost in the woods, you would probably rather try to survive with a bent knife than a broken knife, right? Ok, so we need to figure out how soft we want the knife. People like butchers and hunters know how to sharpen their knives and don't mind doing so. Therefore they want knives a little softer than a guy that can't sharpen his knife worth beans. That guy needs a harder blade so it stays sharp longer. We would need to make his blade a little harder. If we take that hard blade and heat it up to 400 degrees, it would get softer, maybe down to 60 or 61. If we heat it to 425 it will get a little softer, maybe 58 or 59. If we go to 450 it will soften up to maybe 56 or 57. This "Softening" of hard steel is called tempering. You harden a knife and then temper it to the desired hardness for the knifes proposed use. These two processes together are called "Heat Treating." If you grind out a knife, then heat treat it and then start regrinding the knife to clean it up and get it to final polish. You have to be careful not to heat it above the temperature you tempered your blade at or your blade will get softer than you want it to. You would then have to repeat the entire heat treating process to get the hardness you want. There are rules to follow depending on the steel you are using and how you do all of this, but hopefully the idea of why we make it hard then soften it back up makes sense. There you go, a VERY GENERIC definition of hardening and tempering. This was promped by the many questions I get and then the repeat questions do to new people not understanding the difference between hardening and tempering. After this explaination,most get the general idea and can then start asking more in depth questions related to their steel of choice. If anyone has questions, post them here and I will try to help answer them. Last edited by Bob Warner; 10-16-2002 at 07:02 AM. |
#2
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Well done Bob
__________________ Sylvester |
#3
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I don't think I've ever seen it so clearly explained...
Nice job and thanks! Dennis Yeah Baby! |
#4
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Thanks, Bob
Just getting the basic 'idea' of heat treating will be really helpful to lots of beginners. Now at least when (they/I/we) ask a question, the basic terms should be better understood. When I finally got the terms right the rest of the information really started to fall into place. Bob Sigmon |
#5
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Bob, very well presented & almost a definition of how to explain heat treating to beginners.
Which got me thinking: I've noticed that, especially in the newbies arena, that you & a few others are forever answering the same questions (not so bad when the answer could be subjective) but, when it's an objective, or definitive answer, & only then, it could be put in a sticky for just that purpose... ...maybe __________________ colin@britishblades.com
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#6
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Thanks, Bob, for the crystal-clear explanation. I learned quite a bit on this myself. I'm not too proud, or that knowledgable about this.
Can you explain just as simplistically how to differentially harden the blade so that the edge is harder than the spine? Coop PS: This thread needs the title changed to include the words 'Heat-treating and Tempering' for a search's sake. This is too valuable to pass up. |
#7
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Coop,
I changed the title as suggested. As for differentially hardening, have you read the tutorial by Terry Primos? Just go to the how to's and find it. It is explained quite well. OK, now just an opinion here from you guys. Does the oversimplistic explaination help? If you had heard my simple version before hearing any other more technical versions of heat treating, do you think you would have understood more of what the more technical explaination was actually saying? There are so many different ways to explain this that not everyone will understand them all. You can get so technical that nobody will get it or so basic that it is useless. The first thing I ever read on heat treating probably still would not make sense to me. It had charts and graphs and a lot of filler material that just made the book thicker. Maybe I should write a "simple" explaination on some of the other things I get questions on. |
#8
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Bob,
Excellent- we really should have some FAQ's here on the CKD... perhaps this could even go in the tutorials? Only thing I would add is that when you mention the oil getting us to an 80 it might be helpful to the beginner to understand that hot brine or cold water could get us to a 100 but would likely crack / shatter the steel... just so they understand why the oil is only getting us to an 80. |
#9
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Bob, excellent explanation. Now, please explain how to make money on the stock market and, if you've got time, how to understand your mate.
I'm certain several guys will be interested in your wisdom. All kidding aside, thanks for a great, simple, clear, understandable and memorable explanation of a challenging subject. Jayhawk John Athens, Ga __________________ Never give up on your dreams. |
#10
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Good stuff. I agree with Jonathan - it might be helpful to explain that when you quench, it is so violent a process that you always run a risk to crack the blade.
Also, many true newcomers will not be familiar with how different C steels are from SS, and you want to point out that this info is only valid for low alloys. JD __________________ "The greatest productive force is human selfishness." Robert A. Heinlein |
#11
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so far, so good bob!
i had hoped that when we moved to this site that the new search feature would preclude a lot of reiteration, but i guess that we should first point it out to new members and teach them how to use it. then, if subjects/threads are not stickies or tutorial length pieces, i like jonathan's idea of an faq section. i've seen them on other sites and they seem to cut down some of the duplication of effort. thanx for your continuing efforts! __________________ wayne things get better with age ... i'm approaching magnificent |
#12
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Actually a lot of questions I get are from people that don't even understand the tutorials. There are too many things in the tutorials that are not explained because everyone assumes that there is already a basic knowledge to some certain level. Even the simple comment of "Quenching in oil" is greek to those that don't know what it is and the concept of salt tanks would be hard for them to understand.
I really considered doing a "BEFORE THE BASICS" series of tutorials on knifemaking that get you to a level that allows the real tutorials to make sense and do it with the same tone of the heat treating one above only in more detail. Unfortunately my time is limited and I can't afford to spend the time writing all of that up without charging for it. Johnathon, you are correct, I could go into more detail and would if I were to write a book or something but I just wanted to get the concept down without confusing it with too much detail. |
#13
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Cryotempering
Bob, I am new to custom knifemaking and devouring as much info as I can find. Thanks for the nice, simplified discussion of heat treatment concepts. One question for you: What can you tell me about cryotempering to -305 degrees? In essence, what does it do for the blade, is it a valuable treatment, etc. I'm talking about dendritic steel that TKS sells in particular. Thanks for any light you can shed on the subject, and take care.
Michael |
#14
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A Newbie Expressing Thanks...
Bob,
I'm a total newbie here, but Terry Primos got me when I saw a picture of his personal tactical... and as he corresponded with me, he tried explaining alot of what he did. Another maker, Nick Wheeler, is in the process of creating a blade for me and he also is providing me with a blow-by-blow on what he's doing and is currently into the heat-treating and tempering stages. As I only collect (at this point) I'm not totally clear on all the processes, even though I've read quite alot. So far, your "simplified" explanation has served to clarify alot more than I thought I already understood. I realize it does take a lot of time to write stuff like you did... but it IS really appreciated... especially by simple cpllectors like me who truly wish to understand what is involved in producing that piece of art we're willing to spend money on... even tho I can't legally enjoy (employ) it in the municipal area I live in... But now I'll know more about what I am spending my money on! Thanks again, and I look forward to reading more on the process that goes in to the creation of such wonderful stuff! joeshredd __________________ joeshredd |
#15
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Hey Joe!
I'm glad you came on over and joined us. |
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blade, knife, knives |
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