I am starting to think cutting is more in the geometry than in the apex...

bluntcut said:
(...)
Too thin and flat bevel can create nasty stiction (food/material stick to blade). Hollow grind helps. Thin but with some convex cutting bevel also lessen stiction. Depend on target cutting material, key is to get the right amt of wedge to stretch material then the apex has an easier job fracture 'stretched' material, and then continue wedge material away from stick to the blade. See ... hahaha, this tastes best when add a pinch of combinatorial optimization.
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I agree with that. I've noticed that apples have a nasty tendency to tightly grip a flat grind or even a thin convex used in halving or quartering them. They're the only thing my Opinel (thin convex grind) won't slice too well, as the blade gets wedged in mid-cut. I've come to prefer a very thin hollow grind for those, as the hollow in the grind seems to relieve that stiction pretty well; the thin & full-height hollow of a Case Sod Buster is perfect for apples. Also noticed the same tendency with watermelons, which feel very much like a vise if trying to use something like a wide & flat chef's knife to halve or quarter them. A narrow (spine-to-edge) and thin, flexible hollow- or sabre-ground blade, such as found in a long fillet blade, handles those much better.


David
 
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The real trick is to go as thin as the steel can support for its given task. More stable steel can hold a more acute angle.
 
And this is a surprise? We've only been discussing this for the last 10 or 15 years...
 
Sadden said:
The real trick is to go as thin as the steel can support for its given task. More stable steel can hold a more acute angle.
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I was reading your post on another thread about your recon 1 you did at I think 14 degrees inclusive or there abouts. Couldn't find that thread again to ask but I was wondering if you have a YouTube channel with video of that knife or pics of it. I love my recon 1 and I wonder what it looks like with the large of a bevel.
 
I found a razor blade at work the other day made from like, 1/128th thick steel. It's like a piece of paper. With an edge bevel at probably 2-3 degrees per side, it cuts like a lightsaber without being all that sharp.
 
Fred.Rowe said:
What is meant by more stable steel? I've never heard the term in relation to steel.

Fred
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The technical term is edge stability. It is the ability of a steel to resist lateral loads without bending or breaking in the very thin cross sections of the very edge of a blade, within the first 0.0005" of the edge. Why lateral loads, one might ask? Well, even when pushing a blade into something, there are always lateral loads on the edge. Steels with high edge stability can handle lower edge angles on harder to cut material. To maximize edge stability, one would maximize strength of the steel (hardness) and minimize carbide sizes and amounts, to a certain point. A little carbide makes the edge more stable, too much makes it break. Large carbides lower edge stability, small ones maximize it. Steels with high edge stability are O1, AEB-L, 13C26, O7, 52100, and similar steels. Moderate edge stability steels are ones such as A2, M2, M4, etc. Low edge stability steels are D2, 440C, etc. If you like a knife to maintain a high sharpness edge, shaving or above, and sharpen at low angles, < 24 degree inclusive, then high edge stability steels have an advantage over high wear alloys. Most people don't us thin enough geometries to take advantage of them. I have a trapper on which the clip blade is sharpened at 7-8 degrees per side with a slightly higher microbevel (can't be seen without magnification). This is a good place for an O1 blade at 63-64 HRc.
 
me2 said:
The technical term is edge stability. It is the ability of a steel to resist lateral loads without bending or breaking in the very thin cross sections of the very edge of a blade, within the first 0.0005" of the edge. Why lateral loads, one might ask? Well, even when pushing a blade into something, there are always lateral loads on the edge. Steels with high edge stability can handle lower edge angles on harder to cut material. To maximize edge stability, one would maximize strength of the steel (hardness) and minimize carbide sizes and amounts, to a certain point. A little carbide makes the edge more stable, too much makes it break. Large carbides lower edge stability, small ones maximize it. Steels with high edge stability are O1, AEB-L, 13C26, O7, 52100, and similar steels. Moderate edge stability steels are ones such as A2, M2, M4, etc. Low edge stability steels are D2, 440C, etc. If you like a knife to maintain a high sharpness edge, shaving or above, and sharpen at low angles, < 24 degree inclusive, then high edge stability steels have an advantage over high wear alloys. Most people don't us thin enough geometries to take advantage of them. I have a trapper on which the clip blade is sharpened at 7-8 degrees per side with a slightly higher microbevel (can't be seen without magnification). This is a good place for an O1 blade at 63-64 HRc.
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Bold my emphasis. For some reason, that makes perfect sense to me. For every action there is an equal and opposite reaction. When you cut into wood, for example, not only will the wood resist the force straight in but also it should also push in sideways to "react" to the wedge of the edge.
Back on topic. Yes, there are things that defeat thin blades. Fortunately, they are few and far between in my edc. Might be the best case for carrying multiple knives that I have heard. I am working on thinning the grind on a Queen slimline trapper right now. It has been slow, hard work, even on diamond. Partially, because it was ground extremely thick from the factory and partly because hogging a lot of metal off of D2 is hard!!! I think Queen may run there their D2 a point or two harder than Benchmade. Point is that sometimes it is not really practical to thin the whole blade down. I think I have it about 35 hundredths right above the shoulder and I just can't stand it any more. But it should still be a good cutter because I am going with a low edge angle.
 
me2 said:
The technical term is edge stability. It is the ability of a steel to resist lateral loads without bending or breaking in the very thin cross sections of the very edge of a blade, within the first 0.0005" of the edge. Why lateral loads, one might ask? Well, even when pushing a blade into something, there are always lateral loads on the edge. Steels with high edge stability can handle lower edge angles on harder to cut material. To maximize edge stability, one would maximize strength of the steel (hardness) and minimize carbide sizes and amounts, to a certain point. A little carbide makes the edge more stable, too much makes it break. Large carbides lower edge stability, small ones maximize it. Steels with high edge stability are O1, AEB-L, 13C26, O7, 52100, and similar steels. Moderate edge stability steels are ones such as A2, M2, M4, etc. Low edge stability steels are D2, 440C, etc. If you like a knife to maintain a high sharpness edge, shaving or above, and sharpen at low angles, < 24 degree inclusive, then high edge stability steels have an advantage over high wear alloys. Most people don't us thin enough geometries to take advantage of them. I have a trapper on which the clip blade is sharpened at 7-8 degrees per side with a slightly higher microbevel (can't be seen without magnification). This is a good place for an O1 blade at 63-64 HRc.
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Edge stability is one of those catch all phrases that we tend to use instead of using the terms long accepted by the steel industry.

Ductility, plasticity, deformation, toughness, elasticity, sheer strength, hardness, compression loading. If the term edge stability is being used one of the prior terms would serve the discussion better and would be more accurate and informative. Even though a group of knife makers in discussion could assume the person using the term, edge stability, meant one of the former it is not really a technical term but instead generic slang.

Just my 2 cents, Fred
 
Edge stability is a term accepted by certain steel using industries, ones that make things from steels that have an advantage in such thin cross sections. This term, like toughness, has been diluted by overuse and use where it didn't apply. Most of the other terms you mention are also used in a generic manner, but that doesn't mean they don't have a specific meaning and can be written off as slang.
 
Edge stability is a catch all which in 13 letters attempts to lead a much more involved conversation. To me its like using "fast car" when discussing why and how a dragster goes fast.
When the term is used most any condition of steel could be in question. I imagine it could be used in suggesting a steel to another maker when asked what steel to use when making a specific shape of knife. But the person would not be anymore informed about the characteristics of that particular steel. He would just know it would suffice in making the knife discussed.
As a knife maker myself, but one with no formal education in metallurgy, I've worked hard through the years to ferret out the knowledge which I never acquired. I believe its important in passing along information and in discussion as well on the forums, to be selective and accurate as we can be in order to get the most out of the subject being discussed.

If you look back just a few years there were many discussions about "edge packing" as well as putting blades in ones freezer, over night, in order to gain more martensite. The industry is rife with misinformation and slang that on its face is detrimental, especially to new knife makers or collectors looking to improve their knowledge.

When I google edge stability I find links to white water rafting but none that relate to metallurgy. :)

Fred
 
Sandvik uses the term “edge stability” as one of the three elements of edge performance:

http://www.smt.sandvik.com/en-us/pr...p-products/knife-steel/knife-steel-knowledge/

From the link (which also has some cool edge photos)


Sharpness

The ability of the steel to support a keen edge with razor sharpness. It also means that the knife will be easy to resharpen. This is important for all knives.


Edge stability

The ability for the knife edge to withstand edge rolling and edge micro-chipping. Rolled edges and micro-chipped edges are the most common reasons for resharpening. This is important for all knives.


Wear resistance

The ability for the edge to resist abrasive wear. This is usually secondary to edge stability issues, such as micro-chipping or edge rolling.
 
How did edge performance turn into metallurgy terminology 101?

Edge stability is a factory of all the modes of failure you listed so how can one of them be used to better explain it when it could not be explained by just one?
 
Fred.Rowe said:
Edge stability is a catch all which in 13 letters attempts to lead a much more involved conversation. To me its like using "fast car" when discussing why and how a dragster goes fast.
When the term is used most any condition of steel could be in question. I imagine it could be used in suggesting a steel to another maker when asked what steel to use when making a specific shape of knife. But the person would not be anymore informed about the characteristics of that particular steel. He would just know it would suffice in making the knife discussed.
As a knife maker myself, but one with no formal education in metallurgy, I've worked hard through the years to ferret out the knowledge which I never acquired. I believe its important in passing along information and in discussion as well on the forums, to be selective and accurate as we can be in order to get the most out of the subject being discussed.

If you look back just a few years there were many discussions about "edge packing" as well as putting blades in ones freezer, over night, in order to gain more martensite. The industry is rife with misinformation and slang that on its face is detrimental, especially to new knife makers or collectors looking to improve their knowledge.

When I google edge stability I find links to white water rafting but none that relate to metallurgy. :)

Fred
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I can't help that people use terms imprecisely. Edge stability does have a specific meaning, as stated above and shown by Sandvik. Toughness works much the same way. I've seen it used to mean anything from edge holding to impact toughness to lateral strength. Rest assured if I use edge stability, I am describing a specific property, just as with toughness. For anyone else, you'll just have to read and see what they really mean. I have found Google to be problematic when researching anything beyond the level of Popular Science. It takes some digging, but it's there.
 
Google, boy was that poor sourcing on my part. Better Face Book, ::(

Theres a big change in perspective needed, in someone who makes knives and than a knife enthusiast or people who enjoy the process of sharpening blades. A maker has need of metallurgy to the point where if he doesn't understand and practice it; his knives will be less than stellar. If I don't measure steel in terms of time at temperature; alloying and its effects, steel structure relative to knife geometry; then I'm not really a knife maker.
Its different language being used. Here on this forum many people would follow a conversation where edge stability is recognized as familiar. When I attend a gathering of smiths the term "edge stability" would never come up. I have difficulty in discussions on this forum at times because of the differing needs or approach.

You are welcome to come to one of our hammerins where I know you would hear all kinds of new words; especially on a poor forging day :)

Regards, Fred
 
Fred.Rowe said:
Google, boy was that poor sourcing on my part. Better Face Book, ::(

Theres a big change in perspective needed, in someone who makes knives and than a knife enthusiast or people who enjoy the process of sharpening blades. A maker has need of metallurgy to the point where if he doesn't understand and practice it; his knives will be less than stellar. If I don't measure steel in terms of time at temperature; alloying and its effects, steel structure relative to knife geometry; then I'm not really a knife maker.
Its different language being used. Here on this forum many people would follow a conversation where edge stability is recognized as familiar. When I attend a gathering of smiths the term "edge stability" would never come up. I have difficulty in discussions on this forum at times because of the differing needs or approach.

You are welcome to come to one of our hammerins where I know you would hear all kinds of new words; especially on a poor forging day :)

Regards, Fred
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You wanted to come back to the playground so lets not start it off by insulting everyone's intelligence.
 
Whole lotta fancy terms and bickering...I just sharpen my knives till they cut stuff well.
Then I cut stuff with them.
The end.
 
Fred.Rowe said:
Google, boy was that poor sourcing on my part. Better Face Book,

Regards, Fred
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Nothing wrong with Googling, but it is something of an art form. Instead of Googling "edge stability," try "edge stability of knife steel." If you give the Google search the context of your question, you'll end up with better results. I agree with you about terminology. People use it differently, so we often end up talking past each other. What would be nice is if we had a sticky with all the key terms properly defined. Then, whenever one of those terms is used in a forum post, it would be highlighted as a link to the exact definition. But that's a Spark issue.

Here's a link to Sanvik's glossary, which I find really helpful:
http://www.smt.sandvik.com/en-us/pr...eel/knife-steel-knowledge/technical-glossary/



Jason B. said:
How did edge performance turn into metallurgy terminology 101?

Edge stability is a factory of all the modes of failure you listed so how can one of them be used to better explain it when it could not be explained by just one?
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I think everyone here agrees that thinner blade geometry and a more acute edge profile will improve slicing performance, though not necessarily chopping performance. The underlying issue is what steel alloy/heat treat will support high-performance blade and edge geometry, and that brings the issue to metal science.

Back to Fred's point about our inconsistent use of vocabulary, I'd say you are mixing up the terms edge performance with edge stability -- at least that's what I get from Sandvik's definition of those terms. Edge performance includes sharpness potential, edge stability and wear resistance. Edge stability is really a combination of strength [ability to resist deformation, such as bending (vs. flexing) and rolling] and toughness (resistance to cracking, breaking and chipping).
 
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