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High-Performance Blades Sharing ideas for getting the most out of our steel.

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  #16  
Old 02-04-2006, 06:36 PM
Ed Fowler Ed Fowler is offline
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First bend was 90 degrees one way, then the blade was turned around in the vice for 90 degrees the other way. We change directin by turning the blade around as trying to push it back the other way is very dangerous. Sorry I did not fully explain.


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  #17  
Old 02-04-2006, 07:22 PM
Coutel Coutel is offline
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Ahh..ok......that makes sense.......

thanks.


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  #18  
Old 02-04-2006, 09:45 PM
Ed Fowler Ed Fowler is offline
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there may be a partial post somewhere, I lost it so starting again.

Kevin: to me flex means move, under the influence of stress. A blade stretches 40 degrees and returns to within ten degrees of straight, does that mean that it flexed 30 degrees and bent 10? When the blade went to 90 degrees and returned to 30 on its own did it flex 90 and bend 30? Sure the elastic modulus was exceeded, the fact that the tool was still useful is the significant information along with the rquired force. I don't know how to resolve the issues about definitions.

Simply put the tang of the blade moved 90 degrees, then 90 degrees in the opposite direction requiring 115 ft lbs of torque this was the registered force when the tear occured at or slightly beyond the second 90 degree movenent, when the force was released the blade returned to within 30 degrees of strainght.

The bend or flex or degrees the tang moved occured over a distance of about 2 inches of the blade as the ricasso and front third of the blade were bound in the vice and fixture for the torque wrench. The remaining 'bend' or curve in the spine of the blade was about a 30 degree evenly distributed curve.

There was no comparison blade that had not been hardened in the event. I would invite anyone who has time to make a couple of blades, identical twins if they can, harden one and leave the other soft and report back.

The word 'tear' came from my man in the lab. who has the blade now and is still evaluating what it is. He used the terms inter granular vrs. intra granular. One is a tear, the other is a crack,through the grain as opposed to through grain boundaries. Which is which I don't know, this was a new deal to me also and I have not researched what it means. The way I see it that is his job. He was very interested in what he saw under the microscope.

I am not sure that the word failure applies, as the blade could have been put back into use by tapping it back straight. It would have had a little drag across the tear, but probably less than the ricasso cut on some knives.

I do not report what we learn for the benefit of customer relations for my benefit. My sole interest is the fact that some day a man or woman could find themselves in a jackpot where their very life or the life of another will depend upon a knife that will stand up to the needed level of performance. The more we debate, the more knife makers who share thoughts and seek to develop better knives, the more what I call high endurnace performance knives will be available.

Kevin, I am not sure if we are debating or discussing or seeking conflict resolution .
I feel that if we could spend a week or so working together or maybe simply a cup of coffee we might come to the same conclusions, even though we might not understand what the other was saying.

Thanks for the time and thoughts shared! If anyone has more to say, join in.


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  #19  
Old 02-04-2006, 11:48 PM
Kevin R. Cashen Kevin R. Cashen is offline
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Quote:
Originally Posted by Ed Fowler
...Kevin, I am not sure if we are debating or discussing or seeking conflict resolution .
I think a debate would have a slightly different structure and dynamic to it, I doubt it can be conflict resolution as I have never had any adversarial or antagonistic feelings for or from you Ed, I have always saw you as a gentleman in all of our conversations. So that only leaves discussion for the best description.

Quote:
Originally Posted by Ed Fowler
...I feel that if we could spend a week or so working together or maybe simply a cup of coffee we might come to the same conclusions, even though we might not understand what the other was saying...
Believe it or not I have always thought that myself, even though the more I try to get a handle on your positions I doubt too many of our conclusions would coincide, I do believe we would both have fun finding out over a hot cup (I love coffee but my body will not coexist with it, so for me it would have to be tea).

My main concern is that folks might see, hear or read "flex" to 90 or 180 and think that the blade returned to true, since most of us think of flex as an elastic type of deformation. Whereas the word "bend" to 90 leaves a lot more wiggle room for things to happen and not have misinterpretation by folks who are looking for just such a blade.

Not to worry, I do not use "failure" in any form of judgement or assesment of quality, instead I use it as a metallurgical term to describe the fact that the material reached its ultimate strength and fracture did occur. It is a general term to cover any form of exceeding the ultimate strength be it fracture, plastic type rupture (compression or tensile) or tearing.

I often get picked apart by metallurgical geeks myself, so I know what they are waiting to pounce on if they can. I get the feeling that you know exactly what you mean to say but it gets lost on me in translation. Consider my tiresome inquiries into specific terminology, as my way of passing on some of my hard learned lessons. Leave them nothing but a direct approach to your position, because the devils in the details and in that war of attrition they will pick at technicalities until the big picture is lost.

One day perhaps our research paths will cross and I think that would be more fun than conflict.

Last edited by Kevin R. Cashen; 02-04-2006 at 11:51 PM.
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  #20  
Old 02-05-2006, 11:47 AM
Ed Fowler Ed Fowler is offline
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Smile

Kevin: I did not mean all the particulars you heard in the various words I used, what say we simply agree to talk about knife stuff.


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  #21  
Old 04-08-2006, 05:54 PM
canyonman canyonman is offline
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Kevin and Ed,

If you guys are in an argument, you are doing a piss-pour job of it. As an uneducated outsider looking in, you both make more sense of it all, than I can absorb, but it sure is fun trying to follow what the two of you are saying. Please continue your discusion, cause it does inspire guys like me to learn more about our past time.

Larry
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  #22  
Old 04-09-2006, 03:34 AM
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Andrew Garrett Andrew Garrett is offline
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This is better than listening to Burt Ruttan and Igor Sikorski debate how best to make a paper airplane!

Lovin' it!


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  #23  
Old 04-17-2006, 08:08 PM
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Karl B. Andersen Karl B. Andersen is offline
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Ed had sent me this picture of his torque wrench and asked me to post it.
(He didn't tell me I had to re-size it!) No problem, Ed. My pleasure.
As you can see, with just the right amount of imagination, is that there are two pieces of flat steel with bolt holes stradling the ricasso area, and one of the pieces has a bolt welded to it to be grabbed by the torque wrench.
Looks to be pretty reliable to me!


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Last edited by Karl B. Andersen; 04-25-2006 at 01:58 PM.
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  #24  
Old 04-18-2006, 12:56 PM
SamLS SamLS is offline
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Talking

I would think the point of failure would be at yield or bending as in 99.99% of all engineering applications. If in the middle of a sword fight my blade bent I would think the end result would be much the same as my sword breaking. Although if it breaks I got two weapons. I'm certainly not going to be given the opportunity to call time out to straighten the blade or weld a broken one back together so I really don't see one as advantageous as the other. The problem I see with the bend test is its a static load which would apply to utilizing the knife like a pry bar. Its not reflective of the knife or materials ability to absorb shock as an impact test would. Is their a criteria of how much impact a blade should absorb. I think the test needs to hold the knife by the handle and impact the blade foreaft and lateral. Since were sipping coffee and simply discussing bladesmithing could someone explain the reason for distal tapers other than lightening the blade. If a knife were placed in bending like the ABS test the distal taper would reduce the cross section of the blade in the clamped zone making it easier to bend due to the higher level of stress at the clamped area, I don't understand the explanation " distal tapers distribute stress " unless your talking of a different loading scheme than the ABS bend test, if thats the case why the bend test? Thanks
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  #25  
Old 04-18-2006, 02:38 PM
Ed Fowler Ed Fowler is offline
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The bend test also comes after the 2 x 4 chop which is a test of shock resistance.then comes the hangig rope cut, which is a test of blade geometry. The bend is meant to (sorry about terms) test toughness, ie the blade won't break when a pry or lateral stress is applied to the blade.

As already implied in this thread, the amount of toughness, or lateral strength is highly significant, until we started using the torque wrench we simply relied on how much strength was needed to flex a blade, now we have a definate index. Some wimpy blades can be flexed with one hand, others take all the strength a man has or added leverage. When I talk about bend, I believe the more restiance the better. I have seen wimpy blades bend when trying to cut the hanging rope or chop the 2 x 4. I don't have much nice to say about this kind of blade.

Distal taper is a good thing in swords, probably, and maybe some fighters, however I preffer other methods of construction.

To me 'distal taper' is not for a using knife, I strongly preffer what I call the Michael Price grind where in the side of the blade thins infront of the ricasso, then swells toward the tip to provide strength to the tip, this is usefull for tasks like digging an arrow out of a tree or prying apart arthritic joints etc. An example of what I call the Price grind can be seen in Puma knives and many older European blades. Somehow I have never noticed this design in English blades, but in German and other European blades it is pretty prominent.

SamLS: You asked some excellent questions!


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  #26  
Old 04-18-2006, 05:50 PM
SamLS SamLS is offline
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Thanks for the reply Ed,

I understand more clearly where your coming from regarding the bending/torque test. When I think in terms of material toughness, I think in terms of impact testing. Automobile ball joints are tested in a impact fixture where a specific size weight is dropped from a specific height on the ball joint. This is to ensure toughness. Not only is the load important as you have characterized with this test but the rate at which the load is applied can also be important. I would like to hear some opinions regarding impact data for knife steels or does the plastic bending of the blade do enough to ensure toughness. I'm thinking in terms of fighting knife or sword tests where you could get a severe side impact in application.

Is this the prince grind you speak of where the blade is wider towards the tip or does the spine of the knife narrow and widen as well (ie the thickness of the blade changes).

http://www.knifecenter.com/knifecent...es/116375b.jpg



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  #27  
Old 04-18-2006, 08:01 PM
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Karl B. Andersen Karl B. Andersen is offline
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I'm going to throw this in and someone can correct me if I'm wrong.
I had distal taper once explained to me in this vane - consider the leaf spring under a car.
It is tapered its entire length both in width and thickness.
If it was the same width and thickness from one end to the other, then when the load increased, there could actually be found a weak spot in the leaf and right there it would break! But, with the gradual increase in load capabilities in the tapered leaf, as the load increases, the load is transfered on up the leaf to the thicker areas - there is NO WEAK SPOT!
It's one long transfer of stress.
Make sense?


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  #28  
Old 04-18-2006, 08:06 PM
Ed Fowler Ed Fowler is offline
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Yes pretty close, on the hunters pal (I believe) the swelling is more blended in to the spine. The spine I like is pretty straight, the difference comes through the radius of the convex grind. Puma makes some well designed blades.

Impact strength is a very illusive variable to evaluate. I once had some blades that came from steel that had been overheated early in its development. The blades outcut any I had made before that time and the edges flexed ten times with no chip. I was elated, then dropped a blade onto a billet of steel and knocked a chip the size of a nickel out of the edge. The blades had all chopped well cured hardwood and aged bone without chipping. They had the characteristic dimples of over heated steel, but due to the testing they had passed, I felt something else had happened. We were months figuring out what happened but were able to develop a system to prevent that event from ever happening again.

There is a lot to learn when it comes to what I call High Endurance Performance blades. Last night I was doing a forging demonstration for students at a seminar. I forged three blades using mild steel with out regard to forging temp, heating the steel to a yellow color, it only took me 18 minuets to forge a blade, this compares to an average of three hours per blade when using low temp, coupled with other thermal cycles.

This is the beauty of the forged blade, there are no limits, you can take the steel many directions. Make Blades that won't bend without tremendous stress, or blades you can easily flex with your hands. Rex and I feel we have taken 52100 as far as we can go in the direction we have been heading for 5 years, now trying something completely different with the steel that so far has led to more questions than we thougth possible.


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  #29  
Old 04-19-2006, 07:54 AM
SamLS SamLS is offline
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A leaf spring is held on two ends and loaded in the center. The ends are allowed to pivot. So in practice you would place the handle and tip of the knife on two blocks and load the center of the knife. How would a knife encounter that loading in practice? A distal taper would help that loading scheme but how does it apply to using the knife? I suspect a distal tapers true purpose is something other than strength.
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  #30  
Old 04-19-2006, 08:34 AM
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Karl B. Andersen Karl B. Andersen is offline
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Of course it is.
I'm only referring to 1/2 of that leaf spring. From the center either direction.
The function is the same on each end.
The load presses down on the small ands and transfers toward the heavier portion as the load increases.


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What do you do when you see your ex in pain, limping and bleeding?

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