Ranking of Steels in Categories based on Edge Retention cutting 5/8" rope

Finally gone through the entire thread of >1,000 posts.....
Great testing and great thread!

I really appreciate Jim Ankerson's (Superman) effort and generous sharing of the data. The results are very clear and easy to be understood. I know that this thread contains 2-years worth of discussions. But I am now interested in interpreting them (the coarse edge results) myself to some extent. I would appreciate any input, correction, or criticism to this newbie.

I guess there are two main factors working in this test: blade steel and blade geometry
(On the assumptions that the variability of individual knives of the same models is small and that the sharpening method works to the same extent on every steel. Ankerson mentioned that he tested several knives of the same model and obtained very consistent results. I also know that he got similar impressions with two Manix 2 LW S110V on another thread. These suggest that the variability of production knives is small and negligible in this test. The efficacy of sharpening is very difficult to quantify and will be ignored here.)

That he tested Mule, Mille, and PM2 knives with different steels is particularly great. This gives us the opportunity to directly compare the performance of the steels, at least those at the given hardness and from the particular manufacturer. From this comparison, K390 seems to be the current winner in this test with S110V as close 2nd (assuming that knives with different steels of the same model have the same blade design/geometry). And maybe S90V, ZDP-189, and M390 following? Can't connect the points ATM...... Also hope to see CPM10V on these knives to compare it with S110V and K390.

Now the blade geometry effect is interesting. I see that it can have a big effect, as shown in his results of Manix LW S110V before and after reprofiling. To me, this is counter-intuitive. Why does a thinned blade retain the edge longer? Is it just because the force needed to push the edge into the medium can be reduced?

But the geometry seems to have relatively less impact on the performance than the hardness has in this test. I guess Mule with S110V (HRc 60) is thinner behind the edge than Manix 2 (without reprofiling) but yet perform poorly against Manix with the same steel at HRc 62. Of course these factors would affect the performance nonlinearly, such that we cannot be conclusive for their effect sizes......

From these considerations, I would go for a steel first, then the hardness, and the geometry of the blade for good edge retention. Then I got Manix 2 LW myself. Although it doesn't get to hair-splitting sharpness like knives with ATS-34 or ZDP-189 I have (but it does bite quite well), the edge retention seems way better than any of those. Again, great thread.


Miso
 
chiral.grolim

I am confused. I understood that the difference in the carbide content between LC and HC steels is not big enough to affect the apex diameter (=sharpness) but does affect the stability of the apex. What confused me is the following statement.

chiral.grolim said:
In non-abrasive cutting of soft materials (e.g. food), high-carbide steel can take the same level of edge refinement as a low-carbide steel, it just requires better (sharper/harder) sharpening equipment, and it will hold that edge just as well as low-carbide steels.
Click to expand...

Why is the edge retention of HC steels as good as, not better than, LC steels in non-abrasive cutting? Wouldn't the binding effect of carbide also be in play in cutting soft materials?


Miso
 
sodak said:
Hi Will,

I was actually serious. I did a lot of testing about 10 years ago on the forum, and documented my process with explanations and pictures, just like Jim has done. I went so far as to take pictures of the UPC's and bar codes at Lowe's so that anyone could pick up the exact same material (Phil Wilson did). I always invited anyone to either confirm or contest my results, it's always better to have multiple people testing. It takes a LOT of time and effort. Jim has documented his process, I think it would be great for someone to pick up the ball and run with it, and post the results. There's no BF rule that Jim has to do it all, we can all try it (myself included), and compare results, especially if they can take the testing to a new level or direction.

I think if someone has a great idea, they should give it a shot. I'd still be interested in the results.
Click to expand...

Hi Sodak,

I apologize for the outburst. It's actually the first of that kind since I've been a member. Not too long before that someone definitely made a smart ass remark to me on a different forum, and in addition to that I was having a bad day. I come to these forums every once in a while nowadays to relax and look at knives, so with the timing and my reading your post as sarcasm, I just lost any interest in being diplomatic. Again, I'm sorry.
 
miso2 said:
chiral.grolim

I am confused. I understood that the difference in the carbide content between LC and HC steels is not big enough to affect the apex diameter (=sharpness) but does affect the stability of the apex. What confused me is the following statement.



Why is the edge retention of HC steels as good as, not better than, LC steels in non-abrasive cutting? Wouldn't the binding effect of carbide also be in play in cutting soft materials?


Miso
Click to expand...

Apex "stability" depends on strength (hardness) and also cohesion of the matrix at the apex, dominated by geometry i.e. apex angle/thickness. A harder apex can achieve a thinner diameter and angle because it is less prone to deformation, takes more effort to achieve elastic deformation. However, when deformation does occur, it is a shorter distance to fracture on the stress/strain curve, i.e. very little plastic deformation, "brittle". A softer apex, i.e. one with lower carbide volume in the apex, will experience elastic deformation under lower stress and more plastic deformation prior to fracture (less "brittle"). In HC steels with large carbides (ingot) there are sections of apex with high carbide volume that are stronger but also more brittle and sections with low carbide volume that are weaker but also tougher. In steels with small carbides (PM) the carbides have more homogenous distribution that improves stability along the entire apex.

The trouble comparing "edge stability" is understanding the threshold-value of endurance for each - is there a detectable and avoidable level of stress which one can endure but the other cannot. From what I've read, one must use very careful (computer controlled) application of force and then narrow the edge-geometry below practical levels to measure some of these differences, limiting the applicability of the findings.
One could consider this similar to Jim's tests here. In the polished-edge tests, it was much harder for him to establish differences in abrasion-resistance from one steel to the next, and we know that differences in edge-thickness have the greatest impact on wear-resistance. Jim's tests are really informative after you first establish a working geometry - how thick you need your edge to be to endure other stresses suck as impact or lateral flex - and then you look for the most abrasion-resistant steel. Jim test of the Opinels shows folk the performance of a blade with very good geometry but suboptimal HT and abrasion resistance for this type of work - those knives did fine in other use.

Which gets to the second part - cutting soft, non-abrasive materials the carbides don't really come into play, you don't need them, so why would you expect to observe superiority of HC? HC has a specific purpose. Would you notice a difference in corrosion resistance between O1 and 440A if you never subjected each to a corrosive environment?
 
miso2 said:
The efficacy of sharpening is very difficult to quantify and will be ignored here.

Now the blade geometry effect is interesting. I see that it can have a big effect, as shown in his results of Manix LW S110V before and after reprofiling. To me, this is counter-intuitive. Why does a thinned blade retain the edge longer? Is it just because the force needed to push the edge into the medium can be reduced
Click to expand...

Sharpness is achieved through sharpening, while it may be difficult to quantify it is absolutely essential prior to comparing performance due to other factors. Geometry, which sharpening creates, always comes first.

Yes, thinner = less force required to cut = less resistance-force from the media being cut = less pressure from abrasive particles in said media against the edge/bevels of the blade => less abrasion. It should not be counter-intuitive.
 
Thank you, chiral.grolim, for clarification.
It was bit tough for a lay person like me, but I think I understood the concept better.

I guess what I still don't understand is the difference between cutting soft and hard materials. The edge still wears in any case, therefore, it is under stress. Then, wouldn't the carbide content still affect the edge retention? Of course one may not detect the difference in real life. But it might become apparent if the edges of LC and HC steels sharpened to their minimum apex diameter.

Or, are you implying that corrosion impact the edge more so than wear in cutting soft materials like vegetables?

Anyway, happy holidays and a happy new year to you and all.


Miso
 
miso2 said:
I guess what I still don't understand is the difference between cutting soft and hard materials. The edge still wears in any case, therefore, it is under stress. Then, wouldn't the carbide content still affect the edge retention? Of course one may not detect the difference in real life. But it might become apparent if the edges of LC and HC steels sharpened to their minimum apex diameter.

Or, are you implying that corrosion impact the edge more so than wear in cutting soft materials like vegetables?
Click to expand...

"Stress" is not the same under all conditions, and different attributes account for resistance to different types of stress.
Under corrosive conditions (e.g. salt-water or acidic substances), the blade, including the apex, may suffer corrosion. In the apex, this weakens the edge and allows it to crumble under very minor cutting applications. That is "corrosive wear" and substances like free chromium in the matrix help to prevent/reduce it. Carbide-content doesn't really have much direct impact here, it a matter of iron-content vs free chromium.
Cutting abrasive materials, particles in the material cut into the steel matrix of the blade (like when sharpening) and plow out steel even at the apex. That is "abrasive wear" and ceramic carbides in the matrix help to prevent/reduce it.
Cutting hard materials puts compressive stress on the apex but this is often turned aside to lateral stress, especially if the apex manages to cut partially into the medium and then wedges, resulting in bent/folded/squashed edges (plastic deformation) if the steel is too soft, or it can result in chipped edges if the material is sufficiently hard but lacks toughness or material support to prevent elastic deformation (strain which can exceed the UTS). Resistance to deformation comes from higher hardness (by definition) and/or geometry (material-stiffness/flexibility is cubically related to material thickness). High hardness allows for thinner geometry (higher cutting efficiency) while maintaining compressive strength.

Cutting soft non-corrosive materials puts very little stress of any kind on the apex of a knife blade unless you make the edge very thin. Most mass-produced kitchen cutlery is fairly soft stainless steel, it is sufficient for cutting soft materials in corrosive environments common in kitchen use. The greatest risk to the edge after corrosion is impacting a cutting-board or other hard surface. If you compared blades of the same steel at 50Rc, 55Rc, and 60Rc under such conditions, you may never notice a difference unless you minimize the geometry of each (the harder blades can be taken thinner for better cutting efficiency) or start cutting hard materials (the harder blades will resist compression but are at higher risk of chipping if the strain-threshold is exceeded). Comparing high-carbide to low-carbide blades both at 60Rc cutting soft materials, they can achieve the same level of sharpness, thinness, you wouldn't notice a difference until you stressed the edge in a noticeable way. For example, if you switched to cutting hard materials or just something too hard for how thin the edges are, the high-carbide edge may chip-out where the low-carbide edge compresses/folds/tears (brittle-fracture vs ductile).
 
If you want to split hair, higher carbide content can, in theory, have an impact on corrosion resistance if those carbides are "excessive" chromium carbides that have locked up some of what should normally be free chromium. That is one of the arguments in the debate over higher versus lower tempering temperatures for stainless steels along with the secondary hardening issue. The funny thing about some of those German factory kitchen knives and their soft medium carbon stainless is that they can apparently flatten, role and chip all at the same time on the same edge. Go look at your non-knifey friends' Henckels or Wusthoff block set and see what I mean. :D
chiral.grolim said:
"Stress" is not the same under all conditions, and different attributes account for resistance to different types of stress.
Under corrosive conditions (e.g. salt-water or acidic substances), the blade, including the apex, may suffer corrosion. In the apex, this weakens the edge and allows it to crumble under very minor cutting applications. That is "corrosive wear" and substances like free chromium in the matrix help to prevent/reduce it. Carbide-content doesn't really have much direct impact here, it a matter of iron-content vs free chromium.
Cutting abrasive materials, particles in the material cut into the steel matrix of the blade (like when sharpening) and plow out steel even at the apex. That is "abrasive wear" and ceramic carbides in the matrix help to prevent/reduce it.
Cutting hard materials puts compressive stress on the apex but this is often turned aside to lateral stress, especially if the apex manages to cut partially into the medium and then wedges, resulting in bent/folded/squashed edges (plastic deformation) if the steel is too soft, or it can result in chipped edges if the material is sufficiently hard but lacks toughness or material support to prevent elastic deformation (strain which can exceed the UTS). Resistance to deformation comes from higher hardness (by definition) and/or geometry (material-stiffness/flexibility is cubically related to material thickness). High hardness allows for thinner geometry (higher cutting efficiency) while maintaining compressive strength.

Cutting soft non-corrosive materials puts very little stress of any kind on the apex of a knife blade unless you make the edge very thin. Most mass-produced kitchen cutlery is fairly soft stainless steel, it is sufficient for cutting soft materials in corrosive environments common in kitchen use. The greatest risk to the edge after corrosion is impacting a cutting-board or other hard surface. If you compared blades of the same steel at 50Rc, 55Rc, and 60Rc under such conditions, you may never notice a difference unless you minimize the geometry of each (the harder blades can be taken thinner for better cutting efficiency) or start cutting hard materials (the harder blades will resist compression but are at higher risk of chipping if the strain-threshold is exceeded). Comparing high-carbide to low-carbide blades both at 60Rc cutting soft materials, they can achieve the same level of sharpness, thinness, you wouldn't notice a difference until you stressed the edge in a noticeable way. For example, if you switched to cutting hard materials or just something too hard for how thin the edges are, the high-carbide edge may chip-out where the low-carbide edge compresses/folds/tears (brittle-fracture vs ductile).
Click to expand...
 
Kaizen1 said:
Hi Sodak,

I apologize for the outburst. It's actually the first of that kind since I've been a member. Not too long before that someone definitely made a smart ass remark to me on a different forum, and in addition to that I was having a bad day. I come to these forums every once in a while nowadays to relax and look at knives, so with the timing and my reading your post as sarcasm, I just lost any interest in being diplomatic. Again, I'm sorry.
Click to expand...
No problem whatsoever! As a lot of these guys can attest, I've done it myself a couple of times too!
 
Do you value quality information? Let forum management know that chiral.grolim's last 4 posts are sticky worthy. He succinctly answered 90% of what newcomers want to know about geometry/steel/heat-treat and their interrelation. Cheers Sir. You nailed it.

Data rules.

^^^Sticky please.
 
I stood abroad for some time, job, I get back and I find some VERY respected knife makers that chime in into this thread!
Chapeau Mr Wilson and Big Chris. And thanks for the beauty and proficiency of your works.
 
chiral.grolim

Thank you for the great insight into the topic. Very informative. I guess my confusion stemmed on the definition of "soft and hard" materials. I would expect to see no difference in edge retention when cutting tofu between HC and LC blades. But then, Jean fabric is said to be hard enough to function as a strop. I consider it a soft material, but it is able to wear steels (although in this case it may be a lateral stress)......

Anyway, I got the point. No more nagging.

So, translating what you explained into sharpening a blade, it seems like having "teeth" and a narrow apex at the same time would make the edge perfect for both slicing and push cutting with good edge retention, particularly with HC steels. Would it be true, or I completely misunderstood something? The below cartoon is what I imagine.

Edge.JPG


To test this, last night I sharpened my ATS-34 blade (20 DPS) with 250 to 8,000 grit stones with small increments in the grit #. It cuts a free-hanging hair and shaves well, but seems slipping on the skin of a tomato or on my palm skin. I then resharpened it with a 1,000 grit stone followed immediately by a 8,000 grit stone and stropping. It doesn't split free-hanging hair but shaves well and bites tomato skin quite well. I don't know about the edge retention yet.

I am sure that this kind of thing has been discussed somewhere in this forum. But I wonder whether this low grit to very high grit sharpening is commonly employed.


Miso
 
miso2 said:
I guess my confusion stemmed on the definition of "soft and hard" materials. I would expect to see no difference in edge retention when cutting tofu between HC and LC blades. But then, Jean fabric is said to be hard enough to function as a strop. I consider it a soft material, but it is able to wear steels (although in this case it may be a lateral stress)......
Click to expand...

Paper is a relatively soft fiber material as is fabric, but both are at least somewhat abrasive, more so if embedded with carbides such as "stropping" compound ;) Verhoeven published tests of bare-leather strops showing no abrasive effect, but others have discussed the fabric strops as "burr-catchers", i.e. they can snag a wire-edge and help remove it to form a crisper apex.

miso2 said:
So ... it seems like having "teeth" and a narrow apex at the same time would make the edge perfect for both slicing and push cutting with good edge retention, particularly with HC steels...

Edge.JPG


To test this, last night I sharpened my ATS-34 blade (20 DPS) with 250 to 8,000 grit stones with small increments in the grit #. It cuts a free-hanging hair and shaves well, but seems slipping on the skin of a tomato or on my palm skin. I then resharpened it with a 1,000 grit stone followed immediately by a 8,000 grit stone and stropping. It doesn't split free-hanging hair but shaves well and bites tomato skin quite well. I don't know about the edge retention yet.

I am sure that this kind of thing has been discussed somewhere in this forum. But I wonder whether this low grit to very high grit sharpening is commonly employed.
Click to expand...

Yes, teeth+narrow apex is ideal for penetration and also slicing. In your cartoon, the difference between the top and middle pictures is less a function of edge-finish than it is apex-geometry - the high-grit apex can be just as fat. The comparison is really between the middle and bottom pictures. Also, the size and distribution of the teeth are important. Think of different saw blades and the TPI-rating: "teeth per inch". For knives, we would reduce this to "teeth per millimeter" and the variety of abrasive grit-sizes produce that via the scratch-pattern. A low-grit finish gives fewer large teeth (e.g. 325-grit 45 micron), a high-grit finish gives many small teeth (e.g. 8000-grit 3 micron). Large teeth well separated penetrate easily but produce a rougher cut as material snags in the valleys - not so good for shaving, carving, general push-cutting - and in cutting harder material, a large tooth may lodge in the material and then be bent/broken via lateral stress. Small teeth closer together do not penetrate as deep as easily but produce a smoother cut more optimal for shaving and carving.

A recommended technique for a high-performance slicing-edge is a relatively low-grit edge followed by stropping to polish those teeth and remove any wire-edges, similar to jumping from 1000-grit to 8000 so long as you don't use the 8,000 to remove the 1,000-grit apex entirely. Anyway, it all depends on how you want the edge to perform in a specific type of cutting. Please forgive this alteration to your cartoon:
Edge.JPG



BTW, anyone is welcome to correct me if my comments seem way off, and also i apologize to those who would prefer questions/answers about edges & grit to go in 'Maintenance, Tinkering & Embellishment' - I advise those seeking such recommendations to check there.


Keep up the good work, Jim!
 
chiral.grolim said:
Sharpness is achieved through sharpening, while it may be difficult to quantify it is absolutely essential prior to comparing performance due to other factors. Geometry, which sharpening creates, always comes first.

Yes, thinner = less force required to cut = less resistance-force from the media being cut = less pressure from abrasive particles in said media against the edge/bevels of the blade => less abrasion. It should not be counter-intuitive.
Click to expand...

To add to this, edge angle has a large effect on edge retention. Thinner edges/lower edge angles cut longer, provided they are strong enough for the application. This effect is strong enough that it can overshadow the steels being compared. Notice that all of Ankerson's tests are done at the same edge angle of 15 degrees per side, thus removing that from his tests.
 
me2 said:
To add to this, edge angle has a large effect on edge retention. Thinner edges/lower edge angles cut longer, provided they are strong enough for the application. This effect is strong enough that it can overshadow the steels being compared. Notice that all of Ankerson's tests are done at the same edge angle of 15 degrees per side, thus removing that from his tests.
Click to expand...

The impact of edge-angle is directly related to material thickness = structural support vs displacement of the cutting medium. In terms of structural support, remember that thickness is cubically related to stiffness, i.e. resistance to deformation that can result in a roll/dent/chip. THAT takes priority. Increasing/reducing edge-angle has a fairly linear impact thickness.

What Ankerson does is control for edge-angle by using that which is most recommended for general utility. 15-dps or 30-inclusive to the apex is the lowest angle recommended for everything from sushi-knives to chainsaw and chipper-blades, it proves an ~2:1 ration of apex height to thickness. Going below this angle more often results in edge-failure, so much so that many knife makers recommend adding a micro-bevel at 20-dps except for very specialized tools. But you will notice that Jim has begun listing the "edge thickness" of various knives to show the power of thin geometry.
 
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