differential tempering or not?

M

McAlpin Blades

Joined
Mar 15, 2001
Messages
82
I have been edge quenching my blades. Am I wrong that common sense would tell me that a fighter or survival knife should be full quenched? Obvious reasons make me ask this. I would rather have a combat or survival blade break rather then bend. If it bends bad then how do you get it back in the sheath? You probably won't. Then what? You carry it in your hands which eliminates the use of one hand in an emergency situation. If it snaps, on the other hand, you can still put it in the sheath and you can put the broken part in a backpack safely and still use it later for cutting such as the cavemen did with flint knives. You can still withdraw your broken bladed knife and assuming you have a little edge left, you can still use it to slice in a fight, although your useable length is obviously hampered, you nonetheless have SOMETHING to use in an emergency which is better than nothing. If i want a blade to pull my body weight up a cliff while it is stuck in a crack, I want the blade to bend first(duh). But for fighting with more to come, say a soldier overseas, I want it to break before bending so I can still have SOMETHING for the next encounter and still be able to have two hands free for my rifle. Just my 2 cents. What do you guys think? Nice to be back. Cory
 
Cory,You are thinking again:D :D :D
A Broken Blade will get you killed in a fight,A bent Blade is still a servicable weapon!!!!!!!!
That is the whole idea behind the differential heat treating.If done properly the Blade shouldnt break in a fight at all.And if you are in a survival situation you definately don't want to loose your knife due to it brealing which can hurt you when it happens causing more problems that you have to deal with.If you are climbimng or something like that you will already know that you may need something to help you climb and thus take something that you have found laying around with you,If you drop this then and only then should you count on your knife to pull you up and if it breaks you will fall and seriously hurt yourself or get killed,Thus a flexable blade.
If you are worried about this then what you need to do is differentialy heat treat the proper way,which is to fully harden the Blade then set it in a pan of water edge down abiut 1/4 to 3/8 inch under the water.Now take a torch and draw the back of the Blade back tp a dark blue to a black,fronn behind the point all the way out the tang.This gives the spine a spring temper thus very strong.It would then be like trying to bend a car spring by hand and almost impossiable to bend.This is the proper way to do the heat treat on your knives to pass the A.B.S.Tests.If you are just edge quenching after normalizing or annealing then you will have a very soft back and thus bendable and it will stay bent,If done the other way you can bend to 90 degrees and have the Blade strighten itself back out to almost straight,And then you can wedge the blade in something and bend it back the other way and almost straighten it out and then it will fit back in the sheath...
This topic has been discussed before so try looking in the archives.Or ask Ed Fowler here on the forums his opinion on this as he has wrote many articles and spent many hours testing diferent heat treatment meathods to achieve the perfect function of the knife..
Even the Swords are soft spined and hard edged for the very reason that a " BROKEN BLADE IN BATTLE WILL GET YOU KILLED AS YOU NO LONGER HAVE A WEAPON<AND A BENT BLADE WILL STILL PROTECT AND SERV YOU ALLOWING YOU TO STILL WIN THE FIGHT"

Just my 2 cents worth here,Lets see what others have to say about it...
Bruce
 
Cory,

Well I guess its what you want in a blade, the type blade your talking about will be a fairly long blade so the strain will be great at the blade-tang junction, so your liable to snap it off right at the ricasso and then you won't have much but the handle. I've tested a lot of my blades and with the quench line 1/3 to 1/2 up the blade from the cutting edge and the spine left soft they will take a lot of abuse. When doing the bend test a fully hardened blade won't take near the pressure to break as a edge quenched blade will take to bend. I've bent blades 90 degrees and more and had them return to about 30 degrees of being straight, without a crack or break anywhere, stuck them back in the vise and straightened back, sure the blade is wavered and not very pretty where it was bent but it is still useable until you can get another. Check out my web site under history and you will see a blade that was bent well over 90 degrees with no cracks or breaks and it wasn't easy to bend either, I started out with both hands and had to get a 2ft. cheater pipe to finish the bend.I would want the edge quenched blade, but thats just my opinion.

Bill
 
I like some steels with a diff temper.
Just finished an EDC with a 52100 diff temered blade.
I like them because they are TOUGH!
 
I guess you guys are right. I thought I heard something like this from a maker once so I wanted to test the theory. Cory
 
The JS bowie that Cliff Stamp tested was differentially heat treated and bent for my Journeyman Smith performance test. When I returned home, I put it on a stump and straightened it out with a hammer. Later on I sent it with a few more to Cliff to do some cutting with.

Whatever you used to bent it one way, turn it over and bend it back.
Works for me and I like it :).
 
You gentlemen covered the subject very well. Strength in a blade that won't break depends upon the mass of the blade as well as the nature of the steel. It is a balancing act and when you test your blades you come to know the steel very well. If it bent you can probably straighten it if the knife maker did his job. There can be no generalizations, all 5160 is not tough, nor is all 52100 it depends on the maker's abilities and devotion to quality control. Not of little consequence is the nature of the knife the client seeks. If he wants heavy duty, we need to know how to make it to serve his needs. That is the fun of making knives. Any kinife will eventually break, but it is within our reach to make blades that will cut very well and withstand 5 1/2 180 degree flexes requiring more force than the average man can apply with his hands on the handle and still be straightened out to serve as a knife.
 
Originally posted by beknives
Cory,You are thinking again:D :D :D
A Broken Blade will get you killed in a fight,A bent Blade is still a servicable weapon!!!!!!!!
That is the whole idea behind the differential heat treating.If done properly the Blade shouldnt break in a fight at all.And if you are in a survival situation you definately don't want to loose your knife due to it brealing which can hurt you when it happens causing more problems that you have to deal with.If you are climbimng or something like that you will already know that you may need something to help you climb and thus take something that you have found laying around with you,If you drop this then and only then should you count on your knife to pull you up and if it breaks you will fall and seriously hurt yourself or get killed,Thus a flexable blade.
If you are worried about this then what you need to do is differentialy heat treat the proper way,which is to fully harden the Blade then set it in a pan of water edge down abiut 1/4 to 3/8 inch under the water.Now take a torch and draw the back of the Blade back tp a dark blue to a black,fronn behind the point all the way out the tang.This gives the spine a spring temper thus very strong.It would then be like trying to bend a car spring by hand and almost impossiable to bend.This is the proper way to do the heat treat on your knives to pass the A.B.S.Tests.If you are just edge quenching after normalizing or annealing then you will have a very soft back and thus bendable and it will stay bent,If done the other way you can bend to 90 degrees and have the Blade strighten itself back out to almost straight,And then you can wedge the blade in something and bend it back the other way and almost straighten it out and then it will fit back in the sheath...
This topic has been discussed before so try looking in the archives.Or ask Ed Fowler here on the forums his opinion on this as he has wrote many articles and spent many hours testing diferent heat treatment meathods to achieve the perfect function of the knife..
Even the Swords are soft spined and hard edged for the very reason that a " BROKEN BLADE IN BATTLE WILL GET YOU KILLED AS YOU NO LONGER HAVE A WEAPON<AND A BENT BLADE WILL STILL PROTECT AND SERV YOU ALLOWING YOU TO STILL WIN THE FIGHT"

Just my 2 cents worth here,Lets see what others have to say about it...
Bruce
Click to expand...

This sounds like the method the Japanese use to make Katana's. I know the accual method is different but similar effect. When you do this to a knife just so I understand correctly. You...
1. Anneal.
2. Harden/Quench in Oil or whateverthe metal needs.
3. Temper? Not sure if this is done before or after the differential
tempering or not. Probably after? Please help.
4. Put cutting edge under water 1/4-1/2" torch the spine until blue or
black tone on metal and then let it air dry. Do you go by the tone
of meta only or time under flame? after metal tone changes do you
let it air dry? How many times do you do this step?

Has anyone ever tried to clay temper a knife like you would do to a sword?I wonder how well it would work. Thanks. I appreciate any help on my questions, this is the only place I can go for advice. Thanks again.
 
First, let me thank you all for an informative thread.

Second, let me thank Ed Fowler for sharing his time and expertise on this forum.

Third, and you knew this was coming, I have some questions. It is my understanding that Ed Fowler espouses an edge quench (i.e. differential hardening)followed by a triple tempering of the entire blade/knife, as opposed to a full quench followed by differential tempering of the spine, ricasso and tang. The proponents of a full hardening followed by a differential tempering ("soft back draw")espouse tempered martensite over pearlite, claiming that pearlite makes for a "wimpy blade," to use a non-technical term. IOW, they claim that edge quenched blades bend too easily in the first place and then "take a set" or remain bent rather than springing back near true. But it is my understanding that this is not always the case, and it is certainly not the case with Ed Fowler, Wayne Goddard, or, for example Rick Dunkerley about whom I believe Ed was talking when he mentioned the 5.5 180 degree bends (yes, Ed, I've been doing my research). So, while I am more inclined to believe that the edge quench is both not wimpy and more precise/exact/accurate than drawing with a torch, I would like to hear from Ed Fowler and others about the methods for edge quenching while still retaining toughness and resistance to bending.

Sorry to go on for so long,

John Frankl
 
Thanks for the questions. I was hoping someone would ask. All edge quenches are not equal! Wimpy blades come from thin blades and shallow depth of hardened steel. Blade geometry is also a prominent player. Bill Burke and I have been experimenting with what I call the modified Michael Price Grind. (if you want to understand what I am talking about check out the Two part series in Blade concerning the John Andrew Clinton Michael Price knife). The blade was thicker from the front half than at the ricasso. It took me a year to figure why he did it, but finally figured it out (I believe) by experimenting with variations of his design. When flexed to 135 degrees, the best experimental blade (4" long) returned within 40 degrees of straight. Within 2 hours it was back to within 30 degrees of straight. The front third had returned to within 3 degrees of straight. The blade's performance was a delight to behold. I gave the blade to Ron Appleton who flexed it 180 back in forth several times and now carries it as a using knife. Judging a blade by any single index of performance is like judging a symphony by one note. All aspects of the blade come together in harmony to result in the desired performance. Bill Burke recently worked up a blade that flexed to 90 degrees with a great deal of force and returned to straight each time. The sky is the limit when you are having fun.
 
Now we're talking. Ed, what months was the Price article run? Also, have you had a look at the Tai Goo/Tim Lively video produced by Ron Hood under the "Hood's Woods" series? In this video they promote a "profile" something like the one you describe, i.e., peaking in thickness about 1/3 of the way back from the tip (say about where the clip/false edge begins on an average bowie)with a distal taper running in both directions from there. I am not sure if this is what you were talking about, but it is a design where the ricasso area is nociceably thinner than the area some inches in front of it.

Also, just to clarify, none of the blades you are discussing were selectively tempered? And what about selective hardening--about how far up the blade are you hardening these days?

Thanks again,

John
 
Thanks for the comments! I haven't selectively tempered a blade for years. Selective tempering did not provide reliable results in my tests. This does not mean someone else can't make it work. The depth of the hardened portion of the blade will vary according to the use the blade is intended for. As a general rule of thumb I like to harden at least 1/3 of the blade, sometimes as much as 1/2. -I have not had a blade crack for years using the multiple quench, so strength is not the only issue. The goal of etching is to provide an accurate visual description of the nature of the steel in the finished blade. If you have read my article in Knives 2002 you will have a better understanding of What For. The soft back is also a safety issue. When I pound on the spine of a blade with a rock or hammer I do not want a spine that may chip. I have not seen Tye Goo Lively video. I don't remember what issues the series ran. I will try to get the answer for you. I feel that Michael Price or someone in his shop produced some of the best designed blades I have seen. Not all knives marked M. Price have the same attributes. Obviously others worked in his shop.
 
It sure is nice to here you say that you havent selectively heat treated your blades in so long Ed.
I don't draw the back of my Bowies Back either,They pass most flex tests but I havent tried the full 90 degree test yet.
Hey ed will a 1/3 or 1/2 quench only pass the ABS flex test...I will be testing soon and am curious about this.You said a few years ago that you wanted to see a Blade that had been fully hardened and the back drew back on the knives that you see when you are testing people for the ABS test...
Bruce
 
Harley,

Thanks for adding that. You are certainly not alone. But I was hoping we could get a little more information out of you. Come on, please, give us some reasons, procedures, results, etc. for your method.

If you have the time and inclination,

John
 
John: you have been doing your homework. It is nice to read from others who explore. The John Andrew Michael Price knife was discussed in Dec 2000 and Jan 2001.

Bruce: The ABS performance tests are mere childs play when it comes to high performance. I remember a time when I felt they were ultimate achievements, actually they serve as intermediate goal, but should not be viewed as the extreme achievement. The ABS performance standards have not been raised since the first days of the organization. Knives can be pushed to much higher levels of performance. The first prerequisite is virgin clean steel with high performance potential. Then comes developoing skill at heat treating, understanding of blade geometry and tenacity to first thoroughly explore all aspects of the steel, then the dynamics of the particular using knife you wish to make. There are no limits to the ultimate knife the limits orginate within the maker.
 
Thanks Ed...I know that the 5160 I use will do the job required .I am also confident that I can make one bend the 90 degrees I will need...Now any tips on how to cut the free hanging rope would be nice,I don't know if I am not putting a agressive enough edge on the Blade or if I am just hitting it in the wrong way....Also who nows where you can buy some 1 inch rope that isnt a fortune?
Thanks,
Bruce
 
Your purchase of a roll of 1" hemp rope could very well be one of your most valuable investments in your future knives. I bought mine from an oil field supply house. I have now purchased four rolls, and at first many remanents (when I oculd not afford a full spool.) Keep the rope clean, store well covered so grit doesn't get into it. Test every knife you make for edge flex, then cut.
I once traded a knife for a roll. Get it any you legally can.

Cutting of the hanging rope depends on the cutting edge, and most importantly the blade geometry. then comes technique, aim your cut about 18 inches past the rope, (follow thru). the sides of the blade must be polished, a highly etched damascus blade may not cut, polish out the etch and it cutsl like a dream. No secondary angle, the edge flows with minute gradients to the spine. Save the cut offs from your practice for testing future blades for cut.
 
Bruce are you going for the mastersmith stamp or the journeymans certificate, and when is your time to go for it. Whenever you go for it, KICK ASS.From what I've read about the ABS tests and heard about your quality of work, you should come through with flying colors. Good LUCK

Bill ;)
 
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