Why all the Opinel rave?

Chiral, I'll be quoting out of sequence to help with the flow....

chiral.grolim said:
Again, that is subjective not objective.

REGARDING SKI, BIKE FRAME AND BIKE TIRE PERFORMANCE....
I'm no expert, but I'd guess one could quantify how those attributes affect the ability of a ski (of a given design under and average skiers body-mass) to grip the snow for sufficient agility while maintaining the lowest friction.
...
Again, not an expert, but I'd assume one desires maximum velocity to be maintained in a single direction, so the frame must be sufficiently flexible to absorb irregularities in the road and the cyclists movements that might alter that velocity, while sufficiently stiff to transfer all peddling-effort in the correct direction.
....
Run some tests on different tire-designs and compare times (a quanitity).
Click to expand...


One would think there are simple direct and objective tests, right?

The problem is that performance always has an element of subjectivity involved by necessity. Skis are not fast until they are skied on by skiers; skier who have technique and a "feel" for the snow. Bikes are not fast. Alone, the can only lean against the barn wall. They become fast only when ridden by a human body and the interaction of that human body against what is, in effect, a massively complex spring system has astonishingly complex interactions with rate the rider will fatigue and the amount of power output they can maintain. Tire tests that exclude riders exclude the problem of road vibration tiring the rider.

As a systems engineer, I raise these examples to highlight the shortcomings of reductionism when humans are a part of overall performance. This is very much the case with knife use. The standard problem with objective reductionist tests is they sweep aside variable introduced by human use, and this gap is one of the reasons why the results of "objective tests" are sometimes objected to by skilled users who counter-claim, "that's not consistent with my experience".

Edge-stability is strongly dependent on apex geometry and from what i understand from Landes' posts (haven't read his book as it isn't available in English yet), you need to go below 15-DPS and use careful application of lateral force and minute-precision measurements to be able to discern superior edge-stability in the Sandvik steels over PM, not really applicable to everyday knife use where too low of an apex angle simply results in edge-rolling or chipping which in either case increases apex diameter and so reduces cutting performance...
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This would be an example of an assertion that I've read to much counter-objections to to accept at face value. Just too many complaints about PM steels going jagged with hard use. Interesting to note, BTW, that Landes himself points to and was a contributor to the "biased" Sanvick page.
http://www.bladeforums.com/forums/showthread.php/344902-Edges-and-Steels?p=3043379#post3043379

No, diamond cannot tell the difference between PM and non-PM steels ;) I freehand with a DMT perforated diamond plate from my aligner-kit, but you could use a DiaFold - light-weight, compact, very effective. It sharpens ZDP-189 as easily as AEB-L (skip to ~18:45)
....
REGARDING CARBON STEEL KNIVES...
A knife like this, it may be an important attribute that it be cheap, i.e. disposable, as it may be lost or used abusively. Also it should be easy to keep sharp or at least very thin as the user may be poorly skilled at sharpening.
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We agree there are 2 big game changers. The emergence of PM steels bends performance curve compared to older large carbide stainless steels. The second is the emergence of diamond hones like DMT (FWIW, I carry a fine DMT credit card and use it all the time.).

Never-the-less, from a product design standpoint, you are falling into the same trap of wrongly dismissing the end user as "poorly skilled at sharpening". This is exactly the point. Advances in diamond hone technologies noted, PM steels are widely and correctly understood to be harder for an average knife owner to hone to a keen edge than fine carbide and carbon steels. Good system engineering and product design demands that the user be understood as a part of the system, not a problem that interferes with it. This is what I was driving at in raising the distinction in the different use cases that knives are designed for.



Yes, Sandvik is very biased. Their summary chart pretends that 13C26 has the same toughness (ranked "excellent") as 1075 tool steel, but data to support that claim? Most stainless knife steels achieve only 20 - 40J impact toughness via Charpy. D2 achieves ~31J @60Rc, S90V gets 26J @58Rc, CPM-3V gets 95J @60Rc, L6-tool steel gets 92J @57Rc. If they can really achieve impact toughness ~90J at high hardness with 13C26, I'd like to see it! Folk would flock to the steel! Or perhaps they rank "Poor - Average - Excellent" all within that 20-40J range, i.e. hardly discernible in everyday (non-specialized) knife use.
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Again, I note that the relevance of the Charpy test to knife toughness as it is experienced by users is a subject that is hotly debated (just as bike tire roll-down tests are hotly debated).

I'm not as anti-objective testing as I may be coming off, btw. It helps so long we can first agree to frame the discussion within use caes (which may include people who aren't expert at sharpening) and as long as we accept that tests that exclude humans from the testing may not correlate well to actual usage.


Let's see if we can seek some sort of Bladeforums harmonium by attempting to edit the Sandvik summary table in a manner that we agree upon.

The 5th law of hierarchies is, "Hierarchies are great, if they're your hierarchies; otherwise, they suck." The same is true for categorization schemes. Some will howl in protest at the 4 categories of course grain, medium grain powered metal, fine grain and carbon. As with any categorization, there are edge cases that break out and overlap. And it's always true that a crude 5 point scale applied to an entire group sweeps exceptional counter-examples under the rug. And it is very, very true that many of the properties will vary wildly depending on heat treatment. Never-the-less, let's see if we can agree on the scoring for these categories as groups.

Can you suggest edits?


COURSE GRAIN
Ex., 440A, 440C, 9Cr18Mov, D2, 19C27, Aus-8
Sharpness: Poor
Edge Stability: Poor
Wear Resistance: Very Good
Toughness: Poor
Corrosion Resistance: Very Good


MEDIUM GRAIN POWDER METAL
Ex., S110V, S90V, S30V, Elmax, CPM 3V
Sharpness: Very Good
Edge Stability: Average
Wear Resistance: Excellent
Toughness: Average
Corrosion Resistance: Very Good


FINE GRAIN STAINLESS
Ex., 420HC, 12C27, 13C26
Sharpness: Excellent
Edge Stability: Excellent
Wear Resistance: Average
Toughness: Very Good
Corrosion Resistance: Very Good


FINE GRAIN CARBON STEEL
Ex., 1095, 1086, 1075
Sharpness: Excellent
Edge Stability: Excellent
Wear Resistance: Poor
Toughness: Excellent
Corrosion Resistance: Insignificant



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.


Toughness
-----
Toughness is the resistance of the knife to cracking. Cracks always start at a weak point in the steel, such as an inclusion or a large primary carbide. So toughness is enhanced by a homogeneous structure that is free from impurities and large carbides. A fine-carbide steel grade will always have higher toughness than a coarse-carbide grade with a given hardness. Toughness is vital for professional and military knives.


Corrosion resistance
-----
Corrosion resistance should be selected to suit the application. Since high corrosion resistance involves sacrifices in edge performance, the best approach is to have corrosion resistance that is 'good enough' for the selected type of knife. An everyday carry knife and a fishing knife will make very different demands on corrosion resistance.
 
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Skimming your post here at the salt mine. Great start with those categories there Pinnah. You can learn a bit just reading them. As I humbly listen, may I *ask*, isn't AUS8 fine carbides or grain? You can get it pretty sharp and it doesn't quickly dull to a working edge.

Now back to our regularly scheduled programming.
lHb9105.gif
 
Dave, the categories are not mine. They're stolen from Sandvik.

I too am curious about 440A, Aus-6, and Aus-8. Many people put them as small carbide but Sandvik, who is in the business of selling very fine carbide steels and who trumps up the problems associated with carbide pull out, classifiies 440A as a course grained steel.

I would love to see a larger set of consensus on adjusting that table for just that reason.

FWIW, I don't think people are really that far apart. I think there's actually good consensus that medium grained PM steels and fine grained steels each have their place as offering different advantages to different situations. In a thread in which the OP asked for advice for a carving knife, Chiram suggested
You want an inexpensive stainless-steel that can take a fine (low micron) edge with ease - Cold Steels AUS-8 fits the bill
Click to expand...

Despite all the bluster, I think we're saying very similar things.
 
Pinnah,
I find myself wondering if you know that in spite of large Carbide pullout etc.

That these metals are all capable of producing a shaving sharp edge?


COURSE GRAIN
Ex., 440A, 440C, 9Cr18Mov, D2, 19C27, Aus-8
Sharpness: Poor
Edge Stability: Poor
Wear Resistance: Very Good
Toughness: Poor
Corrosion Resistance: Very Good

Dovo, For example, a German Razor etc MFger has used 440C on some of their straight edge razors on and off for many years.. Also I can sharpen all of those steels on your last post to face shaving sharp without fear of carbide pullout..

Even Schrade 1095!
Some would last longer than others of course but they can all attain a shaving sharp edge.
 
pinnah said:
One would think there are simple direct and objective tests, right?

The problem is that performance always has an element of subjectivity involved by necessity. Skis are not fast until they are skied on by skiers; skier who have technique and a "feel" for the snow. Bikes are not fast. Alone, the can only lean against the barn wall. They become fast only when ridden by a human body and the interaction of that human body against what is, in effect, a massively complex spring system has astonishingly complex interactions with rate the rider will fatigue and the amount of power output they can maintain. Tire tests that exclude riders exclude the problem of road vibration tiring the rider.

As a systems engineer, I raise these examples to highlight the shortcomings of reductionism when humans are a part of overall performance. This is very much the case with knife use. The standard problem with objective reductionist tests is they sweep aside variable introduced by human use, and this gap is one of the reasons why the results of "objective tests" are sometimes objected to by skilled users who counter-claim, "that's not consistent with my experience".
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In my own field, we have the same concerns about agent-involvement. The technique of one surgeon, while most effective and efficient objectively, may be non-functional for another surgeon. However, this is a training/proficiency concern, separate & distinct. IF that 2nd surgeon became proficient in the better technique, he would be a better surgeon. But what if the first surgeon is uniquely able to achieve such results with that technique? "Standard practice" is to use the best technique that can be utilized by the most surgeons while ensuring that those surgeons are as well trained as possible. We do not settle for simply teaching to the lowest common denominator, we select those able to achieve the highest proficiency, pushing the bell-curve as high as possible. It should be the same for all such tests trying to optimize performance with user+tool. For bicycle racing, i would expect designers to test their designs with selections from top 50% of cyclists and work to build a design that improves their performance. We do not eliminate the human element, rather we EXPAND the human element. If the design helps only 10% of those cyclists selected but is detrimental to 20% and has no impact for 70%, one could try to tease out 'why' for each group then come up with another design that helps 20% or more while being detrimental to as few as possible. That is technological advancement :thumbup:

One should note there that Phil Wilson specializes in high-end PM-steel knives that could probably out-cut all competition by a significant margin because of how he optimizes HT as well as geometry... but his knives are very use-specific, an untrained user could easily break a blade in half NOT because Phil screwed up but because the users training/understanding was insufficient to the task. Not just anyone can be a race-car driver, training is required, proficiency is required. If someone is claiming that some steel is "chippy", they should clarify the HT protocol, the geometry, and the use, and compare it to another steel with those same attributes that is not "chippy" as a control. "Not in my experience" is usually an issue not necessarily because the users are different but because the objective conditions are not the same first.

pinnah said:
This would be an example of an assertion that I've read to much counter-objections to to accept at face value. Just too many complaints about PM steels going jagged with hard use...
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That's why I looked to Landes' own work, a set of objective scientific experiments (as well as those of Verhoeven and others) to help eliminate the subjective element. For example: http://bladetest.infillplane.com/html/summary_of_results.html

pinnah said:
The emergence of PM steels bends performance curve compared to older large carbide stainless steels. The second is the emergence of diamond hones like DMT (FWIW, I carry a fine DMT credit card and use it all the time.).

Never-the-less, from a product design standpoint, you are falling into the same trap of wrongly dismissing the end user as "poorly skilled at sharpening". This is exactly the point. Advances in diamond hone technologies noted, PM steels are widely and correctly understood to be harder for an average knife owner to hone to a keen edge than fine carbide and carbon steels. Good system engineering and product design demands that the user be understood as a part of the system, not a problem that interferes with it. This is what I was driving at in raising the distinction in the different use cases that knives are designed for.
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No, the emergence of diamond hones completely eliminates the difficulty in sharpening one steel vs another, reducing any such issues to user error. The diamond hones ARE designed with the user in mind, which is why they look so similar to non-diamond hones ;). If you cannot sharpen on a diamond hone, designed to be exactly the same as non-diamond hones, then you cannot sharpen on a non-diamond hone either. If you have better luck with Crystolon than diamond, it is just that, 'luck'. The understanding that PM-steels are harder to sharpen to a keen edge is a myth began by folk using the incorrect tool for the job and then blaming the job rather than themselves. Another factor I've seen is folk trying to sharpen a PM blade to 15-dps when the apex-angle is actually 20-DPS, and then complaining that it is the fault of the steel since their non-PM knife (which happens to have an apex-angle of 15-dps) sharpens much more easily! Of course they are having difficulty, they haven't apexed the PM-knife at that angle :p Another issue is sharpening a PM-blade that happens to have a thicker bevel than a non-PM blade. Again, of course it takes longer, more metal must be removed to apex the knife.

It is nice that diamond hones can be designed to be lighter-weight, more compact, more durable than their less-advanced counterparts.


pinnah said:
Again, I note that the relevance of the Charpy test to knife toughness as it is experienced by users is a subject that is hotly debated
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Yes. The test-values have no direct import on knife use other than for large choppers, but they do offer an indication of how a blade might fail if subjected to certain levels of stress. To ignore tham as irrelevant is myopic.


pinnah said:
let's see if we can agree on the scoring for these categories as groups.

Can you suggest edits?


COURSE GRAIN ...(etc)...

...

Sharpness

Edge Stability

Wear Resistance

Toughness

Corrosion resistance
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There is a difference between grain-structure and carbide size/distribution. You seem to be talking about the latter (unless you can provide data on grain-size measurements of the various steels), in which case you should simply specify carbide-sizes and distribution or at least volume-percentage. I think that your examples here are off.

You should not use terms like "poor, good, excellent" as they give no sense of the parameters. Instead, give actual measurable values or normalizations of measured values. Is "good" 2X better than "poor" or 20X or not really noticeable except under very specific conditions that are irrelevant to daily use? Be specific.

Again, "sharpness" is achieved by minimizing apex diameter in order than force can be exerted over the smallest possible area to maximize pressure for cutting. This can be achieved on ANY steel as well as non-metal materials.
Also, serrated, coarse, or "toothy" edges are sharper than non-serrated edges with the same apex angle, they focus applied force onto a smaller area to maximize pressure, which is why they "bite" so much better than fine edges. Your (Sandvik's) notion of "sharpness" needs fine-tuning ;) Steels with minimal abrasion-resistance can be abraded to a fine-edge more easily (depending on the tool) than steels with high abrasion-resistance that require more better (harder+sharper) abrasives.

Edge Stability depends more on matrix hardness and apex geometry than steel-type, so you'll need to specify a standard working angle for a specified hardness, and again it'd be good to provide a comparative numerical value.

Wear-resistance is NOT secondary unless there is a real problem with the steel (as opposed to a problem with how it's being used), certainly not secondary if the blade is primarily used for cutting abrasive materials (e.g. rope, cardboard/paper, hide, etc.). If the blade is for wood-carving or kitchen use, then yes it is secondary, but that is subjective, NOT objective. Keep your prejudices to yourself ;)

Toughness is vital for ANY knife subjected to impact stress against very thin geometry. I am not military but expect my tools to remain intact during use, but I can see how some in certain fields might demand more than I.

Corrosion resistance does not necessarily involve sacrifices in edge performance, as comparisons of 13C26 and 52100 have demonstrated. There are stainless steels that are tougher and more wear-resistant than non-stainless. How you value corrosion resistance is subjective, not objective, do not insert personal bias into various knife attributes. You might as well add 'price' to the equation at that point.
 
Rhinoknives1 said:
Pinnah,
I find myself wondering if you know that in spite of large Carbide pullout etc.

That these metals are all capable of producing a shaving sharp edge?
Click to expand...

Yes, absolutely. But (and correct me if I'm wrong), a) it requires diamond based tools, b) one needs to pay more attention to edge angle (min angle increases with carbide size) and in some cutting applications (like wood), one can expect fast edge degradation due to carbide pull out.
 
wtlj said:
So I'm pretty new to knives and only have a few. Every time I open another thread someone mentions an opinel. I had to know what it was. So I jumped on amazon and looked up the opinel #8, $12.95 what!!! Then the picture popped up and I thought no way is this cheap funky looking thing that popular! So what's all the rave about and what are you guys using this knife for?
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I'm a slipjoint fan, and have always had one in my pocket for the last four decades. Nothing replaces having a sharp edge when you need it. A few years ago, like you, I saw all the recommendations for opinel and ordered a pair from the www, one each in carbon and inox.

I used both for a few days, then turned them over to my wife for kitchen use. She's no knife-nut. After a few weeks of abuse, it was clear that the carbon needed a new home and was cleaned, sharpened, and given to one of my daughters (who already owns non-stainless cutlery) for kitchen duty. I promptly forgot about the one in inox for a couple of years, until my wife asked me to sharpen it for her. About 5 minutes later it was razor sharp again and ready for duty. Turns out, it's her favorite knife, and apparently the only knife she now uses in the kitchen. You could have fooled me, it wasn't showing the battle scars of her other knives, and it was the first re-sharpening I'd done. That was almost a year ago, and it's still pretty sharp.

Something that stuck with me was that my wife could care less what it's made from or it's origin. It just needs to be sharp and cut. She uses it, beats it around by it throwing it in the sink to wash, etc. It held up remarkably well considering that fact, especially when compared to her other kitchen knives costing easily 5~8 times as much.

Do I or would I carry an opinel as an EDC? No, and that's not going to change, any sooner than my wife would start using a slipjoint in the kitchen. Different tools for different needs, but I do think that for it's niche the opinel outperforms it's pricepoint. My wife is happy with hers, and I'm even happier with not constantly having to maintain it. I think it was a pretty good investment for less than $20, but that's just my .02
 
Here is some spider poop I got off the net. It seems to go into sufficient detail without being too abstruse. Just throwing it up to spark more thoughts.

****************************************************************************************************************************
154CM and CPM-154 should both lose their initial sharpness quickly. We're talking about edge stability which is controlled by carbide volume and size. Carbides are the hard particles that contribute to wear resistance but make sharpening more difficult and reduces toughness. Steels with a large volume of carbides lose their initial edge quickly because the edges are only stable when at a certain angle/thickness. After stability is reached the edges last a long time because of the high wear resistance from all of those carbides. Most/all PM steels have a large volume of carbides which is why they're produced with the PM process, to reduce the overall carbide size. This improves edge stability somewhat but the primary factor seems to be carbide volume. This means that PM steels should actually be better, not worse, at maintaining the initial edge. Carbon steels and low carbide volume stainless steels like AEB-L are best at maintaining the initial edge. The long term edge retention, however, is lower.

So if I'm understanding correctly, high carbide volume steels might be excellent for less acute bevel angles and thicker toothy edges, but might not do as well on super thin polished edges or very low bevel angles?


That is correct.
 
davek14 said:
Here is some spider poop I got off the net. It seems to go into sufficient detail without being too abstruse. Just throwing it up to spark more thoughts.

****************************************************************************************************************************
154CM and CPM-154 should both lose their initial sharpness quickly. We're talking about edge stability which is controlled by carbide volume and size. Carbides are the hard particles that contribute to wear resistance but make sharpening more difficult and reduces toughness. Steels with a large volume of carbides lose their initial edge quickly because the edges are only stable when at a certain angle/thickness. After stability is reached the edges last a long time because of the high wear resistance from all of those carbides. Most/all PM steels have a large volume of carbides which is why they're produced with the PM process, to reduce the overall carbide size. This improves edge stability somewhat but the primary factor seems to be carbide volume. This means that PM steels should actually be better, not worse, at maintaining the initial edge. Carbon steels and low carbide volume stainless steels like AEB-L are best at maintaining the initial edge. The long term edge retention, however, is lower.

So if I'm understanding correctly, high carbide volume steels might be excellent for less acute bevel angles and thicker toothy edges, but might not do as well on super thin polished edges or very low bevel angles?


That is correct.
Click to expand...

Steels with a large volume of carbides may lose their initial edge slightly sooner depending on use. What use? How much sooner? Are we talking about 1 meter of cardboard vs 2? Or more like 1 foot of cardboard vs 2? Raw values matter. If we are talking about rate of increase in apex-diameter during a specific use, one should measure it. What rate of degradation constitutes a "stable" apex-diameter (edge)? If one steel achieves that apex diameter faster than another steel and holds it longer, is that "higher stability", or if it 'stably' holds a lower apex-diameter longer (again, relative term) is that higher or lower stability? In what type of use?

In Jim's tests (abrasive use) the high-wear steels hold an apex-diameter below what is required to cut that string w/ <20lbs of force FAR longer than low-wear steels. So are they more or less stable? Perhaps Jim should test how long it takes to increase the force 1lb from initial cutting force. Or perhaps "edge stability" is not applicable to abrasive wear?

By "very low bevel angles" they mean <10-DPS which is only suitable for low-stress cutting, i.e. soft meats, fruits, veggies, soft tissue (surgery), fine hairs (shaving, though not my face), etc. In other words, uses wherein carbide tear-out isn't really going to be a concern anyway :p For wood carving and harder use, low-carbide steels (at low enough hardness) will fold-over and high-carbide PM steels will fold then fracture and large-carbide steels (or low-carbide but very high hardness) will simply fracture. At that point, all have "stabilized" at a much larger apex-diameter but the high-carbide steels remain abrasion resistant and hold their diameter while the low-carbide steels wear steadily away (higher rate of change). So which is more stable?

ALL of this can be mitigated by using the proper apex angle, namely ~15-DPS, whereupon all the steels stabilize (if sufficiently hardened) unless subjected to impact stress whereupon again the large-carbide steels (or those with VERY high carbide volume) fracture more readily than the small-carbide or low-carbide steels.

So if you consider 15-dps "less acute", i wonder what use you put that tool to or if you aren't in fact adding a micro-bevel to support the edge. How thin is required to potentiate a difference?

Again, note how Jim switched to a coarse-finish to potentiate a difference between the steel types. The difference was there already in the polished edges, but in coarse edges ... What is required to achieve that sort of potentiation in "edge stability" tests? If the test is irrelevant to every-day knife use, or if the measurements require a level of precision beyond common experience, then ...


(waiting to see who comes in to answer this)
 
Regarding "Edge Stability" tests, in response to Larrin who gave the answer quoted above, per Roman Landes who published his PhD detailing the subject: http://www.hypefreeblades.com/forum/viewtopic.php?f=3&t=186

Larrin,
For regular blades we make and use, these are the figures you will need for evaluation base.
Edge stability is measured by measuring the cord of a circle out of a perpendicular indent of a hard roll into the edge
To detect real valid differences the angle of the edge must be standardized 20° and assured 100% on each sample.
Each sample must be ground and polished the exact same way till 1 micron polish.
The accuracy of the micro-graphic evaluation needs to be in the area of less than 1/100mm.
Load needs to be 10N=1Kg,
For straight razors and razor blades the figures will become considerable smaller since the area of sharp an dull is smaller to.

In the end of the Day, you need good equipment and a allot of time.
You might find this in a University, you could ask Sherby in Standford or Verhoeven in Iowa or Jeffrey Wadsworth to support you.
Except from good guessing, i don't see much chance to find a easy way to do a cheap and easy edge stability test.
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1 um edge-finish, 10-DPS, applying a 1kg steady load to 10 um area of the edge. That's to test for comparative edge-stability between steels. That's ... challenging, no? I do not mean to denigrate the notion of "edge stability" here, only to keep present the parameters for discussing it such that they can be related to every day knife use. I really want an English copy of Landes' book so I can stop relying on internet posts and vague anecdotes or personal interpretations....
 
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The forum quoted by me (a kitchen knife forum) recommended a 20dps or greater angle for larger carbide steels. 15dps was when the "edge stability" problems were noticed.

There is much anecdotal evidence of steels which lose their very sharp edge rather quickly and retain a working edge for some time. A steel like this would excel in a test like Jim's. I still see quite a bit of value in his test.

I think you are presenting thoughtful posts with the one I'll quote once again below impressing me greatly. I don't think I can present a lot of things Opinels are better at besides price. There are a couple.

As Pinnah says, we really don't disagree so much. The discussion is informative as well.

A good knife with decent steel for the price might be a good thing for people other than "price point snobs". ;) A person who wants to spend a lot and get a lot in his knife might want a tool box knife, a knife for his car, etc.

chiral.grolim said:
I have a couple of minutes, so i will try to address just a couple of things:

Achieving a "very fine edge" is first a matter of equipment & skill. ALL of these steels can achieve a "very fine edge", i.e. <1um apex diameter but some may require diamond plates for this. 12C27 achieving a finer edge than S110V is a myth unless you specify your abrasive medium.

Deformation-resistance and impact resistance are a function of grain structure and the size+distribution of the carbides, largely a function of carbon & alloy content and specific HT protocol. Here, more carbon allows a higher hardness for greater edge-strength, but a matrix with more or larger carbides can compromise that strength at very thin geometry. The thing is, very thin geometry already compromises strength via reducing edge-stiffness, hence relying on 15-dps or more in ANY steel at the apex. Any difference in edge-stability between 12C27 and S110V may not be noticeable because the geometry sufficient to potentiate the difference (e.g. ~5-dps) is too thin for applicable use (although I would love to see data demonstrating otherwise).

High-carbide ingot steels can place large sections of ceramic material right at the apex of a blade to give maximum abrasion resistance and strength... except that immediately around those large carbides is a weak boundary that can result in "carbide tear-out" under excessive stress (impact or lateral) hence such steels being "brittle" or "weak" in comparison to others at the same geometry. Using finer carbides mitigates this weakness. As a result, M390 steel can achieve the same edge-strength and impact-resistance as O1 tool steel with the added benefit of corrosion resistance and MUCH higher abrasion resistance... but at what price$$ ?

Finally, abrasion resistance is a function of alloy-content and HT as Jim has noted, in which case there is a substantial difference between the low- and high-carbide steels.

Fine/mid-grain steels dominate in certain markets for primarily one reason - COST. As was discussed regarding cars earlier, there are cheap cars than can get the job done relatively well for less money than a car featuring various upgrades. The question to the end user is whether they are willing to pay extra for the upgrades (when they are actual upgrades and not mere marketing hyperbole).


Jim is testing abrasion resistance and offers a quantitative assessment. Let's have one for edge-stability (Roman Landes' work) too. Then we can get into impact toughness at thin geometry (unless you just want to use Charpy, etc.), and finally we can discuss ergonomics, etc.

If the main issue with Jim's tests is that they compare knives in different price ranges, that is NOT objective. Jim is not assessing what an item is worth to a specific user, just what sort of tool performance a user can expect in one aspect, namely abrasion resistance. Of course the low/mid-grade steels don't perform well. My question is, do they perform BETTER than the high-grade steels in some other test? What test? Please provide a quantitative assessment. Thank you.
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Chiral,

I think we are getting much closer to understanding each other and a shared understanding. I do think that. Difference remain.

I hope you find this conversation as interesting as I do because I'm going to be offline in the next few days. I will sitting on a beach for over a week. I'm taking an Opinel because I know I can drop it in the sand and the sand won't foul it. I'm also going to be on the beach with no internet. If the conversation continues in my absence, and I hope it does, I'll try to drop back in in about 2 weeks.

I know you are doctor/surgeon. While I sometimes wear the hat of scientist, I'm mostly an engineer/designer, which may explain our remaining differences. Old adage that explains the shift.

"In theory, there is no difference between theory and practice but in practice, there is."

I agree with many of your points and observations that follow (which I'm reordering again) but I think they underscore the engineering/design perspective. An issue about production and 2 issues about users.

chiral.grolim said:
One should note there that Phil Wilson specializes in high-end PM-steel knives that could probably out-cut all competition by a significant margin because of how he optimizes HT as well as geometry... but his knives are very use-specific, an untrained user could easily break a blade in half NOT because Phil screwed up but because the users training/understanding was insufficient to the task. Not just anyone can be a race-car driver, training is required, proficiency is required. If someone is claiming that some steel is "chippy", they should clarify the HT protocol, the geometry, and the use, and compare it to another steel with those same attributes that is not "chippy" as a control. "Not in my experience" is usually an issue not necessarily because the users are different but because the objective conditions are not the same first.
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Why is that PM steels have a reputation for being chippy? As you note, you need to know the HT and geometry, both of which are set by the maker. Not all makers are the same and it would seem that not all of them have a handle on the new PM steels. You have to know who's PM steel we're talking about. The same is true about lower end steels too. The difference is, when Victorinox or Case decide to heat their mid-grade stainless to 56Rc or less, all you get is gummy stainless. It doesn't become chippy. That is, the mid-grade steels are so well known that in practice manufactures don't muck it up that much. I would trust Bark River with 3V. But probably not Buck. Not yet. The situation reminds of the late 90s early 2000s in bikes when carbon fiber frames started to dominate. Some early adopters got right and others didn't. Took awhile for production processes to become stable and commoditized. In theory, PM steels may be tough. In practice, they have the reputation of being chippy, as a whole. The search function produces copious stories on this front that, from a design standpoint, need to be accommodated.



chiral.grolim said:
In my own field, we have the same concerns about agent-involvement. The technique of one surgeon, while most effective and efficient objectively, may be non-functional for another surgeon. However, this is a training/proficiency concern, separate & distinct. IF that 2nd surgeon became proficient in the better technique, he would be a better surgeon. But what if the first surgeon is uniquely able to achieve such results with that technique? "Standard practice" is to use the best technique that can be utilized by the most surgeons while ensuring that those surgeons are as well trained as possible. We do not settle for simply teaching to the lowest common denominator, we select those able to achieve the highest proficiency, pushing the bell-curve as high as possible. It should be the same for all such tests trying to optimize performance with user+tool. For bicycle racing, i would expect designers to test their designs with selections from top 50% of cyclists and work to build a design that improves their performance. We do not eliminate the human element, rather we EXPAND the human element. If the design helps only 10% of those cyclists selected but is detrimental to 20% and has no impact for 70%, one could try to tease out 'why' for each group then come up with another design that helps 20% or more while being detrimental to as few as possible. That is technological advancement :thumbup:

...
No, the emergence of diamond hones completely eliminates the difficulty in sharpening one steel vs another, reducing any such issues to user error. The diamond hones ARE designed with the user in mind, which is why they look so similar to non-diamond hones ;). If you cannot sharpen on a diamond hone, designed to be exactly the same as non-diamond hones, then you cannot sharpen on a non-diamond hone either. If you have better luck with Crystolon than diamond, it is just that, 'luck'. The understanding that PM-steels are harder to sharpen to a keen edge is a myth began by folk using the incorrect tool for the job and then blaming the job rather than themselves.
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There's a huge difference between surgeons and the typical user in the farm/backpacking knife market, right?

Surgeons are board certified and have to maintain those credentials. There are no credentials for owning a knife in the farming/backpacking niche. The majority of users won't even own ANY sharpening tool. The majority of the ones that have any sharpening tool will have a cheesy pull-though sharpener or some other gizmo. You know this to be a reality in talking with your non-knife family and friends. A few.. much fewer... with have a traditional double sided stone. And fewer yet will have diamond hones or a "sharpening system". As you soon as you said "diamond hone" and "system", you jumped out of the farming/backpacking niche. (this doesn't mean that no farmer or backpacker isn't an avid sharpener - we're talking the average here.)

So yes... in theory PM steels can be easily sharpened IF the user has adequate skill and IF they have adequate tools. Big if.

And I know you agree with this, which is why when the new user mst asked for advice, you told him (or her), "You want an inexpensive stainless-steel that can take a fine (low micron) edge with ease - Cold Steels AUS-8 fits the bill ". Spot on.


With respect to microchipping, you wrote:
That's why I looked to Landes' own work, a set of objective scientific experiments (as well as those of Verhoeven and others) to help eliminate the subjective element. For example: http://bladetest.infillplane.com/html/summary_of_results.html
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I followed the link and perused the site (I've seen it before) but not following what you're referring too. I'm not at all following the logic you're attributing to Landes that seems to suggest that PM steels are stable in the 15-20 DPS range given that Landes (as I understand it) preferred fine grain steels like 12C27. This is a part of the converstaion I hope we can continue when I get back.

Regarding to edits of Sandvik's categories, we can, I think, drop that. It will just lead to more confusion.

I think, in the main, we agree on these points...

1) there is an overall difference between PM and fine carbide steels like 12C27.
2) With good manufacture and adequately good user talent and adequately good sharpening tools, PM steels offer some real advantages in many situations.
3) For mass production and for general public sharpening skills, fine grain steels offer the possibility of attaining keen edges easier.

Phew...

And this is why Opinel uses Sandvik 12C27 (like Landes often did).

Now... if Bark River decided to offer an convex ground folder with a lock ring and blade in 3V...
 
More spider dung...

http://www.spyderco.com/forums/show...bide-steels-as-influenced-by-the-carbide-size

Has some good pics of Chromium vs Vanadium carbides.

http://www.cliffstamp.com/knives/articles/edge_stability_review.html

Please read this one, a quote.

Dr. R. Landes explored this subject in detail among other issues on cutlery steels in "Messerklingen und Stahl"4. Landes is a knifemaker and metallurgist who specialized in cutlery steels. He did extensive and quantitative work in what he defined as edge stability which was identical to Johnston's defination of edge integrity. Landes measured the deformation of edges at the same edge cross section in response to microloading. He classifed steels into three groups, type I, type II, and type III mainly based on carbide volume, 0.5-5%, 5-15%, and greater than 15% respectively. These groups needed different angles to both take and hold a high polished sharpness, 8-12, 12-20, and 20-30 degrees per side respectively. The greater the size and volume of carbide, the greater the angle required to keep the edge stable. This was the exact same conclusion reached by Johnston in his less formal, but still as equally accurate, field trials. Switching to a P/M version of the same steel will also slightly enhance edge stability but according to Landes is a small influence compared to hardness and carbide volume. Essentially the P/M has a more consistent edge stability at the same average value of the ingot steel. Landes work also showed in detail proof of carbide tear out in the high carbide steels such as shown in a high magnification shot on the right. He also showed that secondary hardening in steels such as ATS-34 lowers edge stability compared to the equilavent hardness from a low temper.
 
chiral.grolim said:
Steels with a large volume of carbides may lose their initial edge slightly sooner depending on use. What use?
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This is a thread about the Opinel.

The Opinel was introduced in the 1859s as a farming knife. I was made popular in the US when it was imported by backpacking equipment pioneer, Early Winters in the early 70s. Direct competitors in this niche include(d) knives like the Victorinox SAKs, the Case Sodbuster and Ulster BSA knives (since relegated to obscurity). Cutting tasks typically include some combination of cutting wood, food prep and cordage cutting. They weren't made specifically for all day cutting of abrasive materials like carpet, drywall or rope. The expectation for sharpening is that the average user will have low to moderate sharpening skills and will have, at most, a traditional wet stone.

It's fine to talk about other uses such as day long cardbox box cutting, carpet laying or working on a boat, but as soon as we do, we're really talking about uses the Opinel wasn't built for. Those uses aren't illegitimate. And nobody is going to disagree that other knives built for that might be better for those purposes.


ALL of this can be mitigated by using the proper apex angle, namely ~15-DPS, whereupon all the steels stabilize (if sufficiently hardened) unless subjected to impact stress whereupon again the large-carbide steels (or those with VERY high carbide volume) fracture more readily than the small-carbide or low-carbide steels.
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Bingo.

The issue with farming/property work or backpacking/bushcraft/survival uses is that impact stress can be expected. So, given that you're far from your diamond sharpening system and you've just dinged your blade and maybe you've just lost your pocket stone and you need to get a working edge on your knife, what kind of steel do you want? This is a valid reason why farmers, many workers, backpackers, climbers, bushcrafters (who honestly, worry me a bit), survival types (who honestly, scare me a bit) tend to prefer small carbide and carbon steels over PM super steels.

Nobody that I'm aware of is saying that PM steels don't offer real advantages. But like a race bike, you need to be good enough to get that performance out of them. It's a matter of user skill and equipment availability.
 
pinnah said:
Yes, absolutely. But (and correct me if I'm wrong), a) it requires diamond based tools, b) one needs to pay more attention to edge angle (min angle increases with carbide size) and in some cutting applications (like wood), one can expect fast edge degradation due to carbide pull out.
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I think you have gotten some misconceptions of the CPM process and what the benefits are>

Finer grain structure and reduced carbide size.

This is from the folks at Niagara Speciality metals where I buy most of my knife steels.

" The CPM process offers distinct advantages over conventionally melted steels. Alloy segregation is minimized and the process produces a very fine microstructure. Cutting applications where edge toughness is required is improved greatly by the CPM process because of the elimination of large carbides. You can also use a much higher alloy content in CPM steels which improves the toughness and or wear resistance the knife. CPM steels make blade fabrication easier for the knife maker because of consistent heat treat response, predictable size change after heat treating and excellent grindablility. The most popular CPM grades are CPM S30-V and CPM S35-VN. CPM S35-VN which is a martensitic stainless steel designed to offer the best combination of toughness, wear resistance and corrosion resistance. It is a variation of the popular CPM S30-V with a chemistry that makes it easier to grind and tougher overall. Some of the vanadium carbides are replaced with niobium carbides which results in an alloy that is 15 to 20 percent tougher than CPM S30-V without a significant drop in wear resistance."

http://nsm-ny.com/index.cfm?fuseaction=page.display&page_id=27

Diamond stones make sharpening ALL knife steels easier but I sharpen my custom CPM-154, CPM-S30V etc on my knife belt grinder at 30% speed with A/O belts and a dip in the bucket before each pass no problem and I and others can achieve shaving sharp edges with Natural stones, Arkansas and Norton India Silicon carbide stones as well.

Diamond is the hardest element in the Mohs scale but other elements will also sharpen steels at 55-64 RC Here are a few of the others.

ONE.jpeg
 
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