Friction Forged test blade

Wayne G. said:
The 10V was less than .010 in places, the FFD2 was .015-plus, kinda hard to measure because the sharpening land is wider on the thicker blade.
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Those are actually fairly thick for a non-chopping knife. I run 0.005" and under, full primary.

gunmike1 said:
I stopped using and worrying about the scale testing when I noticed in trial runs how much the numbers were jumping around for me...
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It is too imprecise, what you are measuring is cutting ability not sharpness. The total force is F_0+F_b where F_0 is the cut force at maximal sharpness (wedging) and F_b is the increase in force due to blunting. A few simple ratios will show you the precision is very low and subject to massive deviations as you noted.

...
and how the thinner D2 blade was cutting with less force even though the edges were pretty much equally sharp as measured on newsprint push cutting and slicing, as well as shaving and how cleanly the rope was being cut.
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Yes, if you want to make this point really absurd, have Krein regrind a 420J2 blade and watch it easily cut hemp rope WAY better than a FFD2 blade with a 0.015"+ thick edge. Thus the solution is to buy a knife for $20, have Krein regrind it and it will easily outperform a FFD2 blade costing 10X as much.

Steel does not cut, this is a complete case of "the emperor has no clothes". Geometry cuts, all steel does it better allow you to optomize geometry. If you decide not to, or pick the wrong steel then the performance is poor. This is why a steel like 420HC can easily offer BETTER performance than 440C as a cutting steel.

I guess I just don't have the experience or skill to get good results with the scale testing yet.
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It is impossible to get very precise with it, it is just a matter of math. Anyone who thinks otherwise needs to do some blind cutting to wake up to the reality of the precision. When you first press the knife into the cord that is the force needed for the F_b at maximum sharpness, it is less than a lbs or so. Yet this is only about 5-10% of the total force, this means that all the rest of the force does nothing but reduce precision. This is why I modeled the curves to separate sharpness from cutting ability. I then switched to the sharpness measurements directly to improve precision as you noted.

-Cliff
 
The reason the twine cutting shows little difference between a thicker blade and a thinner blade with the same edges on them is the twine is already cut before it sees the different thickness. This problem can also be mostly prevented with thicker rope by just cutting closer to the ropes end. Think of trying to cut a paper thin piece off. I think for the average home knife nut the scale is a very good way to measure force. I also made a rope holder and it worked great for me. All I did was drill a hole in a 2x4 and stick the rope through and cut it. I think Waynes rope test is a very good, and repeteable test, even though Cliff and his sheep complain about it.
 
Wayne, thanks for the test results. Yes I agree that the thinner blade will do better for a lot of reasons. That is also my experience. I also know from that hardness will goveren as well. But what this test shows is a comparison of a FFD2 blade as furnished by the manufacturer at the standard hardness (66-67) and edge geometry and a 10V blade made by a certain custom maker at a std hardness (63) and edge geometry are pretty much comparable for cutting rope up to about 25lbs pressure. 25 lbs is past the point where most people would want to re-sharpen a blade. It is a good estimation of how both knives will perform in the field. The FF blade is very hard, in fact harder than most files. The metalurgy and edge geometry is such that it is still tough (strong) enough to work in a slicing mode with out edge damage on big game. We will await your future testing on some different steels and thanks again for the work. PHIL
 
db said:
The reason the twine cutting shows little difference between a thicker blade and a thinner blade with the same edges on them is the twine is already cut before it sees the different thickness. This problem can also be mostly prevented with thicker rope by just cutting closer to the ropes end. Think of trying to cut a paper thin piece off. I think for the average home knife nut the scale is a very good way to measure force. I also made a rope holder and it worked great for me. All I did was drill a hole in a 2x4 and stick the rope through and cut it. I think Waynes rope test is a very good, and repeteable test, even though Cliff and his sheep complain about it.
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The whole point I was making was that I wanted to measure the retained sharpness of each particular steel (the whole point was to compare the steels, not the grinds), which the twine does well for the reason you noted. For actual cutting ability, which includes the geometry and knife grind in the mix the scale test works very well for Phil and Wayne, but as Wayne says he tries to keep the geometries as identical as possible when comparing different blades. Otherwise you will have a very thin knife beating out a thicker knife that actually retains it's edge sharpness better. I was just trying to compare the steels, not the grinds. I think reading over Wayne and Phil's posts they are saying the same thing, that a significantly thinner knife will have an advantage in the scale test. Add to that my inability to keep the scale from bouncing around and the test wasn't working very good for me, and I chose to cut the twine, which matched up well with my other sharpness tests like newsprint, ect. Call me a sheep if you want, I am just doing my best to do some rope testing for the first time.

Mike
 
gunmike1 said:
Add to that my inability to keep the scale from bouncing around and the test wasn't working very good for me...
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These scales are not meant for serious measurement. In fact if you press on them hard and let them relax they will rarely return to zero. I had a lot of noise with them, you can see this in the early runs compared to the much more precise twine measurements. Of course measurement of any kind is MUCH better than "cut until it looks dull" or similar.

-Cliff
 
My testing scale is a 1950's model with a magnifying lens. It’s heavy enough with the cutting platform that it doesn’t move under the cutting pressure. It’s accurate on the high end, who cares if it doesn’t sit at zero each time.

The scale isn’t the issue. The issue is running each blade to the same degree of dullness. The scale accurately measures the point where the edge no longer is biting into the rope.

Yes Cliff, your prefer your .005 edged blades made of cheap steel. You stay being the critic and some of the rest of us will be making knives for serious hunters and the like. The Phil, Wayne and Maynard Testing School is concerned with the working knife. Phil is the filet knife specialist and no one that I’ve seen does it better. Maynard and Wayne are testing working hunting knives. We’ve been at it long enough that Maynard has a knife of D5 that he has used on 54 big game animals since I made it in 1980.

Wayne G
 
Wayne G. said:
Yes Cliff, your prefer your .005 edged blades made of cheap steel.
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My knives are not made out of cheap steels, not all of them anyway. Many are custom made out of M2, 1095 and yes even steels like 10V. But yes, I would prefer a knife made from 420J2 at 0.005" than FFD2 at 0.015". The geometry cuts, you are just wasting it at that thickness unless you are chopping.

-Cliff
 
Cliff Stamp said:
My knives are not made out of cheap steels, not all of them anyway. Many are custom made out of M2, 1095 and yes even steels like 10V. But yes, I would prefer a knife made from 420J2 at 0.005" than FFD2 at 0.015". The geometry cuts, you are just wasting it at that thickness unless you are chopping.

-Cliff
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Cliff wrote: "Thus the solution is to buy a knife for $20, have Krein regrind it and it will easily outperform a FFD2 blade costing 10X as much."

That's what I called "cheap" steel. I thought you were recomending it. You need to check your math. FFD2 is closer to 20 times more expensive than $20.

Wayne G
 
Wayne G. said:
That's what I called "cheap" steel. I thought you were recomending it. You need to check your math. FFD2 is closer to 20 times more expensive than $20.
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Ok, then it will outcut the knife which costs 20X more then. Yes I would always recommend better performance in general, I don't care about fads or name branding.

The idea of inexpensive steels being automatically inferior is also hype. 13C26 has FAR better edge stability than S90V. It is also much tougher and easier to grind.

13C26 is thus much BETTER for many applications in cultlery while also being cheaper. Of course feel free to dispute this with any relevant FACTS which oppose what I noted.

-Cliff
 
Cliff,

When you talk about edge stability in a certain steel ... how about stating the hardness and edge thickness.

Also, where are you measuring the edge? And at what sharpening angle?

When you talk about chunks falling out of the edge of D2 blades, are these the ones you prefer at .005 thickness?

Wayne G
 
Cliff Stamp said:
I just posted a link with a simple SAK outcut many S30V knives in terms of edge retention on hemp rope due to the much greater edge stability. Here again a "cheap" steel offered far superior performance because the properties are in fact significantly superior. Ref :

http://www.messerforum.net/showthread.php?t=34401

-Cliff
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Very interesting.
But I did not see anything about blade geometry, surely it played a role in the outcome of the tests. It does say that they kept there respective angles, but that does not tell me what they are. Did I miss the info somewhere?
 
I think the edge angle was put on with the Sharpmaker. So either 15 or 20 degrees per side. Very interesting since that is above the carbide falling out levels, and the edges should be stabil at those angles/thickness. I'm not sure I understand it. It surely confuses more than it clears anything up.
 
magneto said:
Very interesting.
But I did not see anything about blade geometry, surely it played a role in the outcome of the tests.
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Quote (translated)

"The measurers were sharpened all on the Sharpmaker and thereafter taken off on shaving sharpness."

Wayne G. said:
When you talk about edge stability in a certain steel ... how about stating the hardness and edge thickness.
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Edge stability is a property like wear resistance.


Also, where are you measuring the edge? And at what sharpening angle?
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I measure the edge behind the bevel, the edge angle depends on what I am cutting. If it is soft materials like cardboard it will be < 10, if it is harder materials like metals/bone it will be <15. This also depends on the steel as well, harder and finer steels (carbide/ausgrain) will allow finer angles.

When you talk about chunks falling out of the edge of D2 blades, are these the ones you prefer at .005 thickness?
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The edge thickness would not matter as much as the edge angle itself as the carbides are in the micron level so the edge stabilizes very quickly. Long before it is worn back to the primary.

-Cliff
 
It is a materials property of the steel. You would not ask for example, "When you say the steel is corrosion resistant, what thickness of steel are you talking about?". You could however ask things like "What would be the mass loss due to oxidiation ..." on a given surface area.

-Cliff
 
Wayne G. said:
It&#8217;s accurate on the high end, who cares if it doesn&#8217;t sit at zero each time.
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If it does not then you get a systematic error (or random) depending on the zero-intolerance specifics.

The scale accurately measures the point where the edge no longer is biting into the rope.
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Not if it isn't zero'd properly, this would be the definition of accuracy. I however was talking about precision.

In regards to edge stability, I first heard this discussed by Johnston on rec.knives, later read it defined independently by Landes who noted it was studied in about the 50's in Germany. A review :

http://www.cutleryscience.com/articles/edge_stability_review.html

and Landes introduction to the topic :

http://www.bladeforums.com/forums/showthread.php?t=344902

This is his edge model PDF file :

http://forums.swordforum.com/showpost.php?p=845203&postcount=83

-Cliff
 
Cliff Stamp said:
It is a materials property of the steel. You would not ask for example, "When you say the steel is corrosion resistant, what thickness of steel are you talking about?". You could however ask things like "What would be the mass loss due to oxidiation ..." on a given surface area.

-Cliff
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Thanks Cliff. I agree with your assessment of corrosion. We generally can measure corrosion rate for a specific material/environment combination. Generally this is reported at mass loss/time (like you stated) or a penetration depth/time if a more localize type attack like crevice, pitting or intergranular corrosion. Corrosion is generally not a standardized material property because there are so many variables.

I see edge stability very similar to corrosion, e.g. many variables, so I have a hard time calling it a "material property". Am I missing something? Hww do you define it or what is there a standardized measure or approach?

Thanks,

TN
 
tnelson said:
Corrosion is generally not a standardized material property because there are so many variables.
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Yes you would need to specify the type, for knives it almost always means Q-FOG.

[edge stability]

...is there a standardized measure or approach?
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You mean as noted by an accepted governing body, no I don't think so. Landes measures it similar to charpy toughness in the sense something is done to a specific prepared sample and something is measured. The exact nature of the same and details of the testing are noted in his book. It measures the resistance to micro-chipping. I do not think that Landes has quantified it in the sense he has a numerical rating defined, i.e, 440A is 55 SU and 440C is 35 SU at 10 degrees. It just takes too much time, he noted something like 4 months for one steel (many measurements, sample preperations, angle variations, etc.) . He is working on a new book which explores that in more numerical detail.

-Cliff
 
I continue to follow this debate with some amusement. All the references to Landes and testing is fine as far as it goes. Jack O'connor wrote long ago about choosing an expert to get advice about picking guns and ammo for hunting various types of game. At the time a great debate raged between him and Elmer Keith over the proper bore size and bullet weight needed to kill large game reliably. Jack promoted smaller bores at higher velocities, while Elmer touted big, heavy bullets at moderate velocities. Jack said something like "pick your expert and then go hunting." If it works, use it, if it does not then try something else. In other words go find out for yourself what works for you. Too many variables exist to ever produce a certainty for any given situation.

This does not mean all testing should stop, or that the scientific method has no value. It simply means life is complicated so pick something and go with it. You can spend countless hours testing if you like, but in the end human truth is often found in the application.

Last weekend I used a Busse Leaner Meaner Street to help with my barbecue operations. I skinned alder for the wood smoker, cut pork spare ribs, and to show off, I stuck the knife into various trees and twisted the blade out 90 degrees to the left and right. I was not surprised when the tip did not break or bend, and I was not surprised when I found chips in the edge. The chips most likely came from hitting small, hard inclusions in the alder bark, but regardless of how they were produced they existed none-the-less. I say I was not surprised because INFI and SR101 has chipped on me before. In fact INFI has chipped on me more than any other steel. There's a simple explanation for this though. I use it more and I use it harder than any other steel. So when I hear that S30V chips easily I laugh because even the best stuff chips pretty easily if it hits the right thing at the right angle with enough force.

Guess what? I will still use my Meaner Street (I sharpened the chips out in no time). I look forward to buying a FFD2 blade for similar activities. Only after I have used this material the way I normally use a knife will I be prepared to pass any kind of judgement on it. This is not to say I don't find the testing results from Wayne, Phil, and others useful. I do. I even look forward to reading Cliff's test results with a FFD2 blade. But in the end the expert I pick to choose which knife I use is the one writing this long winded opinion. :)
 
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