blade quenching fact or fiction

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I usually use a "reverse distal taper" on the edge. Like Ed says, it gives it strength at the tip... and a finer edge up close to the hand for close work. It's been around a long time. I've seen it on quite a few "primitive" knives.
 
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Me too, Tai.

Most of my blades have the "Price" grind, though I didn't know it had a name until this particular thread. Thanks
 
I would first like to apologize to Ed for not getting in on this forum before now. I have been a very busy boy.

I just got home from spending about 9 days with Ed, and his group of jolly henchmen. I don't have the words to express how much I learned, what a great group of guys I worked with, how impressive the knives are, and Especially, what a knowledgeable, bright, talented, (and the list could go on and on) guy Ed Fowler really is. I feel like I got at least 95 years worth of experience handed to me on a golden platter. Nothing, and I mean Nothing, is held back. I learned everything from welding a bar of 52100 onto a handle of mild steel (so you dont have to use any fricken tongs), to how they make the best sheathes possible. I could just sit here and type "WOW" a hundred and fifty thousand times to give you some idea.

Interestingly, the question of how Ed's blades hold an edge compared to S30 was something we tried while Ed must have been out working on irrigating part of the Willow Bow. If I told you the whole truth, nobody would believe it. Safe to say that the first blade I produced under Ed's tutelage out cut S30 by 2 to 1. That is really a vast understatement, but one that could be proven every single time. A Sebenza was the other test subject.

I really wish I could sit here and tell you all about everything that went on during my stay, because to any knife guy it would be riveting. I'm busy making knives now, but I'll try to pitch in as I'm able.
 
Tie: You are correct that the "Price grind" has been around since the beginning of time in stone artifacts as well as in copper, bronze, silver, steel and wootz blades and more. I call it the Price grind because it was one of his knives that brought me back to reality.

When I first started making knives I used the complex convex grind (reverse distal taper), then took some ABS classes and learned about the distal taper. I thought I was in error using the complex convex grind and went to distal taper. It only took a few test blades to realize the fault in design of the distal taper when you want a knife to manifest supreme strength.
 
Ed Fowler said:
A full distal taper results in a weak tip. The Price grind provides strength to the tip where it is most needed.

When you look down on the spine of one of our blades you will only see at most a slight distal taper.

Blades with a full distal taper tend weakener toward the tip where they need to be stronger.
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Thanks Ed! I totally get your point about a full distal taper weakening the tip.

But I'm still not groking how far up the bulge extends on the Price grind. I was Googling your posts, and a gentleman on another forum was showing how he starts with a thick blade, and then rocks the belt from the belly back into the ricasso at the blade. Is it like the compound taper of a ship, where the spine tapers, but the body bulges at the mid-point of the belly?
 
Lazlo: I believe you have the idea. measuring the spine of our test blade, it measures 0.20 at the ricasso and 0.175 one inch back from the tip. Not much distal taper at the spine but then the spine thickness flows to 0.15 1/2 inch from the tip, 0.135 1/4 inch from the tip and then flows smoothly to the tip.

The complex convex grind flows up from the cutting edge according to the intended purpose of the knife.
 
Rick/Everybody,

Just wanted to let you know that I have re-written the hardening portion of that article on my website...hopefully I've clarified it so there will be no future mis-quotes/misunderstanding on my meaning/intent.
 
Thanks Ed. Mis-quote? No.... Misunderstanding? Yes. Your updated version should remedy that. I do find it quite ironic that a passage with the purpose of advocating the edge quench, helped in steering me away from it. Stange how things work out.

For the record, I agree that the edge quench is a great way to ensure your blade passes the ABS Test. Where we differ is our definition of "hard use". I don't consider a 90deg flex to be hard use. Infact, I don't find it useful in any situation outside of the ABS Test.

My next project is going to be to find out how many foot pounds of torque a fair sized fella can dish out.... and design a hard use knife that can take it... without much flex. That would be useful, IMO.

Rick
 
Where does using clay on the back of the blade during quenching fit in to this. Does it have the same effect as "Edge Quenching"?
 
Years ago we tested a blade with a clay back hardening. The hamon was pretty, but the blade broke catastrophically like a piece of glass on its first flex at about 40 degrees flex. I have never seen a report or photomicrographs which demonstrate the advantages of the clay back being used in hardening as an advantage in knife flexibility or toughness using current methods from an empirical view. I would love to see the claimed advantages put to the test by others.

I fully agree that our testing methods are extreme, most going far beyond what most consider normal use of a knife. Still it is my belief that we never know the limitations of the knives we make until we periodically test a representative sample of our knives to destruction.

We have invested our time, materials and methods at a cost of over $75,000 had we paid others to do the homework.

After reading accounts of survival in extreme conditions we have added testing blades in environments of over 110 f. and below -30 f. We tested chopping ice and digging in frozen ground, as well as buttoning with a rock, tested using in our vice with a torque wrench, not to mention sharpening in these environments.

Our goals include safety through design, ease of carry, comfort to the hand after long periods of use and simplicity of design in accord to use.

If your goal is an art knife which will never be used these tests are an unnecessary investment of time, materials and expense. Our goal is an ultimate survival tool and we take this goal seriously. The kind of knife you chose to make is your choice.

I thank whose of you who have taken you time to wade through this thread and welcome your thoughts.
 
Thanks for explaining that Ed. The reason I asked is I watched Wallie Hayes video on home knifemaking. He made a tanto neck knife from 1/4" 01 Stock and heat treated it with a clay covered back.

I thought the video was nice for a new knifemaker and then at the very end of the video he put the little tanto in a vise and a bar on its handle and bent it 90*. When I saw that I was wondering if it gave the same results as the edge quench.
 
Eh... I don't get this... what's wrong with quenching the whole blade? Would it just be too hard and brittle? And if I try to edge quench... then it's just to dip only the edge into oil, and then submerge the rest right?
 
AVigil said:
Thanks for explaining that Ed. The reason I asked is I watched Wallie Hayes video on home knifemaking. He made a tanto neck knife from 1/4" 01 Stock and heat treated it with a clay covered back.

I thought the video was nice for a new knifemaker and then at the very end of the video he put the little tanto in a vise and a bar on its handle and bent it 90*. When I saw that I was wondering if it gave the same results as the edge quench.
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Yes it does.... Wally is a good friend and knows his stuff.

I spend a lot of time at his shop. We took a 10" blade that I made with a full quench, tempered spine.... put it in a vice and bent it 90deg both ways, then twisted it torsionally almost completely 90deg. It had taken a set of about 3degs to the left, after all was said and done. During the cutting tests I chopped apart an old deck and severed a couple 3" nails with no dammage

Combining modern metallurgical science with good geometry can allow even the novice maker to achieve seemingly "magical" results. I had only been making for one year at that time. The great maker's and guys in lab coats did all this work for us new guys.... I thank them and honour them by taking their hard work seriously.
 
Minebear: In our testing any blade that has been fully hardened can and will ail catastrophically (into two pieces) when it fails. We have tried one full quench followed by two edge quenches - blade failed, two full quenches followed by one edge quench - it failed. Thus the rule I live by - each and every hammer blow, every thermal cycle is forever recorded in the steel.

The blades when edge quenches followed a full hardening quench did not all fail immediately. One looked a little promising for a while, but the crack did not split to a Y at its apex at the bottom transition zone, but continued slowly to the spine, in six months laying on my bench it broke in two.

Any time you heat a blade hotter than 1,725 f. while forging you can grow gain, this is why we call 1.625 our top forging temperature and never intentionally heat above that temperature from the first forging temp to the last. The finer the grain you develop in your steel the lower the temperature at which it can grow. We find that you cannot overdue the number of forging cycles as long as you walk the narrow thermal band from just below critical (when the steel quits moving under your hammer) to 1625 f. You can recognize that temperature when the slag that comes off of your blades is very fine (like powder snow). I usually heat a little below the formation of slag.
Our last student forged at least 5 blades and you could not fill a teaspoon with the slag on and around the hammers and forge.
 
Post #14
Ed Fowler said:
It would be very easy to get into a great debate on this subject, but I will simply suggest that you do as I did and try various methods, test the knives to destruction and see for your self which works for you and the kind of knives you want to make.
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Post #15
(Reply by Bladsmth ) "I agree."



This thread could have ended at one page if this had happened.

I think all know that Ed and I differ on our approach to hardening blades.
I believe that both methods will produce a good blade.
Ed feels that only his method will produce a good blade.
I completely agree with Ed that if people want to test this out , they should make some blades and test them. If one is superior to the other, or if one "Catastrophically Fails" in testing, go with the one that seems best for you.
As for changing each others oppinion......to each his own.
 
Ed, I have maintained the fact that I respect your motivation to make the best knife you can.

However.....

These last few exchanges have forced me to rethink my opinion about you, sir. I am still a novice when it comes to metallurgy but have enough of an understanding to realize your motives are less than honourable. Your blatent disregard for even the most basic metallurgical FACT is stiffling. I have read more boldfaced lies in this thread than any other.... and I'm starting to think that it is because I never reallly read your previous threads. I have no doubt that your motives lie in selling YOUR KNIVES and Discrediting honest makers in the process. Your "ace in the hole" is most people's general lack of enough metallurgical knowledge to see you for what you are. I will refrain from telling you what I think you are.

I am sorry for doing exactly what we are trying to avoid in Shop Talk. If this thread gets closed, it will be my fault as Ed seems to know how to ride the line of personal attack and insult...... he has had a lifetime of practice.

I'm sorry Stacy.

Rick
 
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Here is a fact.

All steels of the same given shape will flex the exact same amount until they reach their elastic limit. IE
A fully hardened untempered piece of 1095 and a piece of spring tempered 5160 will both flex the exact same amount under the same force until failure. Just that the 1095 will quickly fail.

Better example. Make 3 bars of steel 1"x12"x1/8" (or any other sizes as long as they are identical). 1 of 1095, 1 of 5160 and 1 of mild steel. Drill an identical hole in one end of each. Temper the 1095 at 400 the 5160 at 450 and leave the mild steel bar alone. Clamp all 3 bars exactly the same. Place a indicator on each at the same spot then hang 10# on the end of each. Hey, they will move the same amount, hang on 20# and all will give same reading. Keep adding weight and you will keep getting the same readings, eventually the 1095 bar reach its elastic limit and snap, the 5160 and the mild steel will continue to read the same until the mild steel takes a permanent bend, but until it does it will read the same movement with the same weight as the 5160. The 5160 has the superior elastic limit.

The only thing that changes how much force it takes to flex ANY steel with any HT is geometry. You can only change the failure point (elastic limit) and type of failure by using different steels or heat treatments.
 
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We have talked alot about using a knife and bending it until it fails. Of course we never judge a "Crow Bar" on it cutting ability :)

While traveling through Guatemala you will come across many people carrying and using machetes. These machetes are the tools of their livelihood and often the only thing these guys bring to work. When I was there 30 years ago I talked to worker and he showed me how the good machete's could bend 90* and spring back 100% true. He said if it stays bent it is a "Bad blade" and never buy it. They would choose their blades litererally by placing the tip on the ground and pushing on the handle and until it had a large arc in it and springs back. Another thing you will see is many men with only 1 arm. They like to drink and often get into matchete fights :eek:

I still have 2 of those matchete's and use them all the time they hold an edge and do not chip. They cost $8 each :)

So my question is when a knife is used as a cutting and stabbing instrument as designed, bending and prying aside, will full hardened and edge quench both work just as well when you treat the knife as a knife and not a pry bar?
 
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