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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making.

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  #1  
Old 11-29-2008, 03:05 AM
edy5dms edy5dms is offline
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Questions on Quenching and Tempering of knives

Hi everyone,

I'm planning to make my own Ray Mears woodlore type knife using an old file by annealing and turning it to flat ground stock.

I have looked in to all stages of knife building but have not come across any good info on tempering the knife after quenching.

So I would really appreciate if you guys could share your knowledge and tips on tempering the knife. Specially the techniques used and please elaborate on the techniques where possible.

About quenching knifes I?ve seen some people using clay on the spine of the blade like the Japanese do on their swords to have a softener spine and a hard edge. Is this a good practice? Also is tempering still required if quenching is done this way. Please share your thoughts and knowledge on this.

Also any further tips on any of the prosses on knife building are greatly appreciated.

Thank you in advance
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  #2  
Old 11-29-2008, 08:16 AM
SIXFOOTER SIXFOOTER is offline
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I am not an expert by any means but I have been reading a lot lately. Get a copy of "The $50 Knife Shop" by Wayne Goddard. He details Quenching and Tempering and I understood it. The basic idea is you heat your blade uo to critical and either quench the whole thing and then Temper the whole thing, OR, Heat it up and quench the edge, them temper. There are several ways to go about it
The clay thing is 1 way, it keeps the spine soft and the edge hard. I believe that is also how a "Hamon" is done.
Smarter guys than me will pipe in
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  #3  
Old 11-29-2008, 09:50 AM
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Bob Warner Bob Warner is offline
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Search the site for 1095 or 1084 tempering. Assuming your file is a good steel file and not case hardened, these tempering process will work. The bad thing about using files, especially if you are new to knifemaking, is you don't really know what you have so your tempering may be off a bit and not give you the results you want.

Now, you should really have several files that are identical so you can destroy one after completing the process so you can tell if your heat treatment worked as desired, otherwise the knife may fail in use.

Danny,

I knew it would not take you long to start answering questions. You are right about the hamon line and the clay, you can get that by edge quenching also. Smarter guys? Not really just more knowledgeable on this topic.


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  #4  
Old 11-29-2008, 12:20 PM
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Both Bob and Danny gave you some good advise. Follow their suggestions and you'll be on your way. This whole knifemaking thing is basically a lot of experimention anyway, and that's the fun part.
OT: Bob Warner! Good to see you on the screen! Have you found something you like in the way of a profession? Every time I see a motorcycle accident I think of how narrowly you escaped very serious injury from yours. I'm not saying that yours wasn't serious, if anything yours was a lot worse than serious. I know you had a really long recooperation time, and will probably never get over it. Enough of my babbling, how are you doing now?


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  #5  
Old 11-29-2008, 02:45 PM
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chiger chiger is offline
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Hey Edy,

The guys are right. There is already a ton of stuff posted on here about heat treating and tempering 10** series steels. Some of it is even good advice! ;~0

The first thing I'd want to know is how old is what you're calling an old file and what brand is it? Because if it's at least 20-25 years old it may be W1 and not a 10 series steel. They are both shallow hardening steels, but some 10 series and ALL W series steel must be water quenched to reach maximum hardness. You can oil or better yet heated brine quench them and they'll still get plenty hard and it will substantially reduce the risk of cracking.

As far as keeping the spine flexible, Ed Caffrey has a tutorial on his site the best I remember on differential quenching. It's for a deep harding steel I think, but the process is the same. It's probably going to be a more effective process for file steel than a straight clay quench. Probably get a better grain structure the way he does it.

Tempering...no matter how you heat and quench any file steel at home, it must be tempered. Quickly! Have the oven preheated and RUN don't walk to get it in the oven after quenching. Don't stop to admire you work or polish it up...just off to the oven with it. And a couple of cycles won't hurt.

Start with a lower temperature, say 350-375 for a couple hours. turn the oven off and let the whole thing cool to room temp together. If' you test it (Theres a brass rod method posted here somewhere that works pretty good) and it's still to hard, you can always put it back in 25 degrees hotter. Once you go to high on temper temp though....you can't take it back. You have to reheat and quench it all over again or live with it being too soft.

Good luck Edy. If this is your first attempt, you're about to enter a strange and wonderful world from which there is NO return. ;~)

chiger,
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  #6  
Old 11-29-2008, 07:06 PM
Doug Lester Doug Lester is offline
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I know that I sound like a broken record when it comes to using mystery metal for knifemaking, especially by beginners, but a cheap as 10xx series steel is from Admiral Steel, why frustrate yourself trying to figure out what may or may not be a certain steel that was used at one time to make something with. That file could be 10XX or W series steel, but it could be just case hardened low to moderate carbon steel that has been case hardened, in which case it will never hold an edge. I would advise that you get yourself a piece of steel bar that you know what it is and have fun. Getting a copy of "The $50 Knife Shop" is a great idea too.

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  #7  
Old 11-29-2008, 10:04 PM
son_of_bluegras son_of_bluegras is offline
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Files generally fall in one of 2 classes. One is case hardened mild steel. These don't last long as files and don't make good knives. The other is plain high carbon steel. These include W1, W2 and 10XX. For the purpose of knives there isn't enough difference to amount to a hill of beans between W1 and 10XX where XX is 60 or higher.
From here on out assume the file is high carbon since you won't get anything worthwhile from case hardened.
The heat treating begins with normalizing. (Some people anneal, I've had good luck with normalizing). This means heat to critical (just a bit hotter than non-magnetic). You can see this if there is little enough ambient light. Then air cool.
Next comes hardening. Heat again to critical (you can clay coat first, I don't have the experience to speak on it). Some people swear you need to hold it there for some time. I've found 1095 (what I use most) and most files don't need more than a few seconds and unless you have a temperature controlled oven you're not likely to have the ability to hold so don't bother. If your file happens to be an alloy with a touch of V (or similar) you will need to hold for some time (I had one old file that I held above critical for about 45 seconds). If you find this is needed don't worry about grain growth as the alloying element will likely retard grain growth (and may have been the reason for its use). Now you need to quench. While the W in W1 and W2 stands for water, for thin cross sections (like knives) water may be too fast and oil will suffice. Some claim you can't get good or consistent results unless you use quench oil. I get good and consistent results from used cooking oil warmed to around 120-140 F. It does take practice. It also requires you move with a purpose as you have something under 1 second to bring the temp of the knife from critical (somewhere around 1450-1500 F depending on the alloy) to below 900 F. Now test to make sure you got the steel hard. If a sharp file skates, it is hard. You should remove any scale where you test and if it doesn't skate initially, there may be some surface decarburazation in which case file just a bit more.
Now you have a choice to make. Most people recommend tempering ASAP. I stick it in the freezer over night. This may not do anything or it may transform more austensite. Either way you'll need to temper. I do this in an oven. Actually an oven inside an oven. Since most ovens don't have precise thermal control, I place the blade in a dutch oven full of sand inside a regular cooking oven. The sand acts as a thermal mass which evens out the temperature. The temperature you temper to depends on what the intended use of the knife is. For something that will just be used to cut (no hacking, prying, chopping etc), I temper to 325 F twice. Yes that is not a type I mean 325 F. For a chopper I go higher and usually soften the spine some with a torch. I can't give and exact temperature because I temper once in the oven to 325 F then heat the spine with a torch keeping the edge cool until the spine is somewhere around blue and let the heat run to the blade to straw or a bit darker. I don't make many choppers.

If you have enough file left after shaping the knife, play with that to practice heat treating. I gather from your post you intend to grind the knife from the file and not forge, so you'll have less to play with. Take all the teeth off before heat treat. Don't create any stress risers when you shape (sharp inside corners).

ron


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  #8  
Old 11-30-2008, 08:45 AM
edy5dms edy5dms is offline
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Quote:
Originally Posted by son_of_bluegras
Files generally fall in one of 2 classes. One is case hardened mild steel. These don't last long as files and don't make good knives. The other is plain high carbon steel. These include W1, W2 and 10XX. For the purpose of knives there isn't enough difference to amount to a hill of beans between W1 and 10XX where XX is 60 or higher.
From here on out assume the file is high carbon since you won't get anything worthwhile from case hardened.
The heat treating begins with normalizing. (Some people anneal, I've had good luck with normalizing). This means heat to critical (just a bit hotter than non-magnetic). You can see this if there is little enough ambient light. Then air cool.
Next comes hardening. Heat again to critical (you can clay coat first, I don't have the experience to speak on it). Some people swear you need to hold it there for some time. I've found 1095 (what I use most) and most files don't need more than a few seconds and unless you have a temperature controlled oven you're not likely to have the ability to hold so don't bother. If your file happens to be an alloy with a touch of V (or similar) you will need to hold for some time (I had one old file that I held above critical for about 45 seconds). If you find this is needed don't worry about grain growth as the alloying element will likely retard grain growth (and may have been the reason for its use). Now you need to quench. While the W in W1 and W2 stands for water, for thin cross sections (like knives) water may be too fast and oil will suffice. Some claim you can't get good or consistent results unless you use quench oil. I get good and consistent results from used cooking oil warmed to around 120-140 F. It does take practice. It also requires you move with a purpose as you have something under 1 second to bring the temp of the knife from critical (somewhere around 1450-1500 F depending on the alloy) to below 900 F. Now test to make sure you got the steel hard. If a sharp file skates, it is hard. You should remove any scale where you test and if it doesn't skate initially, there may be some surface decarburazation in which case file just a bit more.
Now you have a choice to make. Most people recommend tempering ASAP. I stick it in the freezer over night. This may not do anything or it may transform more austensite. Either way you'll need to temper. I do this in an oven. Actually an oven inside an oven. Since most ovens don't have precise thermal control, I place the blade in a dutch oven full of sand inside a regular cooking oven. The sand acts as a thermal mass which evens out the temperature. The temperature you temper to depends on what the intended use of the knife is. For something that will just be used to cut (no hacking, prying, chopping etc), I temper to 325 F twice. Yes that is not a type I mean 325 F. For a chopper I go higher and usually soften the spine some with a torch. I can't give and exact temperature because I temper once in the oven to 325 F then heat the spine with a torch keeping the edge cool until the spine is somewhere around blue and let the heat run to the blade to straw or a bit darker. I don't make many choppers.

If you have enough file left after shaping the knife, play with that to practice heat treating. I gather from your post you intend to grind the knife from the file and not forge, so you'll have less to play with. Take all the teeth off before heat treat. Don't create any stress risers when you shape (sharp inside corners).

ron
Thank you all for your answers and I learned at least a thing or two form each reply. The reason I have to stick to using an old file is because I live in Sri Lanka and can?t find good and readily available place to buy flat ground steel preferably something like 01 tool steel.

Special thanks to Ron and chiger for taking the time to elaborate on this topic.

Ron-
The file I'm most probably going to use is a very old file made in England from my friends dads workshop which has been there for quite a long time, so from what I gathered from you guys it will probably be a W type. I will only get to select a couple of old file 2moro when I go visit my friend so will know the brand and stuff 2moro.
Also your idea of using an oven in an oven is quite neat; I most probably will toy with that idea cos I was also wandering about how to fix the temperature fluctuation on a normal oven.

I plan to use motor oil for quenching. Would this be too thick, also how is palm oil or coconut oil for this since they are thinner?
Further I plan to get in to the proper blacksmith kind of work with knife later but this kind prject would give me a better start in to this craft and as all you guys mentioned planning to have a load of fun with the project.

Thank you all for your help.
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Old 11-30-2008, 10:04 AM
edy5dms edy5dms is offline
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I have another question.

When I was doing my research I came across many people mentioning that ones the steel has reached its critical temperature at non magnetic level that you have to hold or soak the metal for a further 10-12mins. Is this required and if so how do you avoid over heating the metal and causing grain growth when not having an temperature controlled oven but a only a coal forge?

Thanks in advance
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Old 11-30-2008, 11:18 AM
Doug Lester Doug Lester is offline
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For something like a knife blade with a thin cross section that length of soaking, especially in a forge without any type of temperature control, is not necessarty and probably detrimental to the steel. I soak for no longer than maybe a half a minute after taking the blade out to check that it's non-magnetic.

Back to your original post, it would have been easier to give you a good answere if we had understood that you didn't have a good supply of steel available to you where you live. It looks like that you are going to be forced to use recycled steel. Another source of steel that will probably serve for knife blades are old leaf springs from autos though you may have to find a way to cut them down in width. If you can order "The $50 Knife Shop" from the States it would be a good investment; it's real basic and in non-technical English, if language is a problem. It deals a lot with having to substitute for more traditional tools and materials.

On forging with coal, make sure that it's low sulfer or you can damage the steel. I also assume that you know to burn it to coke before forging with it. Charcoal might be another option for you depending upon it's availability.

For all you guys out there here in the States, I stand by my post on using mystery metal.

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Old 11-30-2008, 12:37 PM
AcridSaint AcridSaint is offline
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The soak is more important with complex alloy steels not used in files. If you can keep your temperature consistent soaking the blade will not hurt it, it's only if you're going over temp that it can cause problems.


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Old 11-30-2008, 11:06 PM
son_of_bluegras son_of_bluegras is offline
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It sounds like you're planning on doing the heat treat with either coal or charcoal. So let me offer another tip. If you use a muffle in the forge fire you'll find it easier to heat the blade evenly. A muffle is essentially a pipe put in the fire and the blade is put in that.
Some time back, I detailed my procedures for heat treat using simple methods. It can be found
http://www.geocities.com/son_of_blue...heattreat.html
There are a couple of pictures that may help you. One is an example of recalescence (don't know how to spell that). Not the best photo but it gives you an ides. This is a phenomenom that will tell you when critical is reached. A magnet can also be used. The other photo you'll find interesting is a shot of a muffle.

ron


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Old 12-01-2008, 04:21 AM
edy5dms edy5dms is offline
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Thanks for your replies all u guys really appreciate it.

Doug lester-

I?m looking to do the knife to about 5mm thickness so i guess it still falls under the category of having a thin cross-section, so as you guys say after checking and confirming reaching the critical heat and then letting it soak for a couple of second before quenching is the way to go with the kind of job and the kind of facilities available to me, correct?
I will look in to the book u mentioned but I'm trying to fit in on a smaller budget as possible cos a couple of dollars in the US is quite a sum over here, but I will look in to it. Also I?ve looked in to the possibility of leaf springs but again to find good one (good steel) like made in the UK or something like that is a bit difficult and now not many leaf spring type vehicle are used and also having to cut it to size is also a problem, so I will try with the file first and see how good it work out but thanks for the idea anyways. The language difficulty of the book probably will not be an issue since I'm a engineering student in university. Oh by the way I'm planning to use charcoals not coal sorry about that my bad.
Thanks for your info and ideas

Ron- Ya I'm going to use charcoal to do the heat treating, sorry about mentioning just coal before

Thanks for the tip about using a muffle; I think it?s a great idea to reduce the variation of the heat on the knife, nice one there thanks. Also thanks for the link.
Also what?s you idea on bevel angle on the blade. As I mentioned before I want to do a ray mears woodlore type blade and is intended for use for bush craft work no chopping and stuff.
I know that the woodlore knife has a 30 degrees overall angle but having seen other knife makers work thought of using about 25.5 degree. What do you think of this?

Thanks
Regards
Dileepa
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Old 12-01-2008, 04:54 AM
edy5dms edy5dms is offline
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I?ve got another question for you Ron, others with experience using old files for knifes please feel free to answer.
Since you have worked with old files as material for your knifes and had suggested 325F temper, how long do you suggest that I keep the knife in the oven? Also wouldn?t tempering twice further reduce hardness? What?s the main reason for tempering twice? Also would 325F be a reasonable temperature to use on my so called mystery steel
Also after removing the knife from the oven is do u just let the knife to air cool to room temperature. Is that correct?
Thanks
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Old 12-01-2008, 07:01 PM
son_of_bluegras son_of_bluegras is offline
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I temper for about an hour each time. The reason for 2 cycles (some use 3) is that there may be retained austentite that converts to martensite when it goes through the first tempering cycle. This results in some small amount of untempered martensite. Then second cycle tempers that untempered martensite. With each tempering cycle there is less austensite and consequensly less untempered martensite. Untempered martensite is brittle. The less of it the better.
Tempering is reliant on temperature and time. Temperature is more important. If you don't exceed the original tempering temperature, the time required to significantly reduce hardness become long enough you likely won't leave the blade at temp long enough to notice a diffenence.
With a temper at 325 F, the hardness is nearly the same as quenched. That means if you got everything right, the knife with have a hardness of 64 or 65 Rockwell C. That is about the same as a file. It is really good for cutting and slicing. As I said before for chopping knives I temper a last time with a torch to color. The 325 would be a good place to start. Temper there then test the knife before you put a handle on it and if you don't like it that hard, or it chips you can go hotter. If you do retemper hotter, go in 25 F increments until you get what you want. I treat usable files as 1095 unless it doesn't harden completely in the quench, then I soak it for 40 or 50 seconds. Since I spark test the files before forging I know those I turn into knives are suitable.
After taking the blade from the oven you can either let it are cool or you can cool it in water. It won't hurt either way.

As for the angle of the bevels (primary and secondary), that depends also on use and type of grind (convex, flat or concave).

ron


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