Anyone ever try doing edge retention testing on their own?

[marrenmiller]

Surely the lower the angle, though, the better the knives performed overall. That's what I've always found.

The thing is, it probably does but I couldn't tell much of a difference in the feel of the edge after I was done. After 40 feet of cardboard, every knife I tested was at the level where I would have resharpened it in normal use, even K390/Maxamet/4V at low edge angles. Maybe they would have kept cutting cardboard and paper easily, but the edges of all of the knives, no matter at 20 dps or 14 dps, felt trashed to me.

I'm positive there will emerge a clear difference with repeated testing. I'm just surprised at how little of a difference there is when doing a single test.

 

[marrenmiller]

This point is significant. Cut testing is tricky business and there's a lot more to it then meets the eye.

That sure is the truth. You could basically pick any point to stop at in any of these tests I've done and not be wrong. It's entirely subjective, it seems. I think a lot of the value in the cut testers that have been doing this a long time is that they've gotten good at identifying the point at which that they feel a knife is done with a test. It might be subjective but they seem to be able to determine that point for them consistently, at least.

 

[marrenmiller]

Did more testing yesterday and found that my Manix 2 in M390 did better on the second trial. It did seem to hold a razor edge better than the ZT, cutting around 20% more cardboard before stopping. It's been sharpened fewer times than the ZT, so maybe I'll need to keep using it and testing it. Also, I still maintain it feels better to sharpen than the ZT.

I need to find a tape that stays on the blade better during cut tests.

 

[marrenmiller]

Regarding edge thickness, its something I've certainly been trying to wrap my head around.

Steel is pretty hard. Most of the things that most people cut are soft and not abrasive.

Dirty cardboard is full of sand and grit which are extremely abrasive.

Clean new cardboard is not abrasive, well it is slightly, but cardboard basically is cellulose, and it's not doing much to dull a knife without pressure.

On a 600 grit edge, almost any knife steel can cut in excess of 1000 feet of clean new cardboard if using the blade from heel to tip, back and forth, slicing your way through. I've personally tested this with 420HC on a Kershaw Dividend. After 1000 feet it was still easily slicing through copy paper.

That test demonstrates that cardboard isnt doing a whole lot to wear down steel.

When you tape off the blade, only exposing an inch of it, and push cut your way through the cardboard, everything changes. You're primarily testing the effects of the compressive forces of the cardboard against the apex.

That is possible, but I still haven't seen anything conclusive that determined the edge thickness factored into edge retention. The best controlled test I've seen was from Super Steel Steve and determined there was no difference between two otherwise identical knives, with the only variable being edge thickness.

 

[ktataragasi]

The thing is, it probably does but I couldn't tell much of a difference in the feel of the edge after I was done. After 40 feet of cardboard, every knife I tested was at the level where I would have resharpened it in normal use, even K390/Maxamet/4V at low edge angles. Maybe they would have kept cutting cardboard and paper easily, but the edges of all of the knives, no matter at 20 dps or 14 dps, felt trashed to me.

I'm positive there will emerge a clear difference with repeated testing. I'm just surprised at how little of a difference there is when doing a single test.

This brings up an important topic though . At what point do most people for edc consider their knife to be dull? This is a question I have asked myself several times. I remember long ago if my knife cut anything I was happy. Now over the years I can sharpen it to shave but should I expect it to stay there or should I expect a working edge. And what is a working edge? You can make most knives perform most tasks even if dull. Yes it can be dangerous to have a dull knife but that "trashed" edge could still cut up boxes. So what is a reasonable level of dull and when should we touch up our knives? I know knives that I now consider to be not sharp I have handed to people and they have been amazed at how sharp it was.

I think at the end of the day we are all just knife loving individuals who somewhere down the line started to expect too much from our knives.

 

[Larrin]

I wrote some about thickness behind the edge here: https://knifesteelnerds.com/2019/02/11/can-catra-predict-rope-cutting-performance/

 

[marrenmiller]

I wrote some about thickness behind the edge here: https://knifesteelnerds.com/2019/02/11/can-catra-predict-rope-cutting-performance/

Saw that. Thanks Larrin.

I want to note, however, that I'm very intentionally not considering cutting ability in these tests, at least as how I understand Catra testing works. I don't regrind knives, and I don't normally bother to do microbevels, so for my uses I am trying to only look at what wear occurs at the very apex for a better comparison between knives. I'm making no consideration for how much force it takes to cut things, like Ankerson or Cliff Stamp do, as then I'm just comparing too many things at once. Those are important considerations, to be sure, but it's not something I'm interested in getting into.

 

[Larrin]

Saw that. Thanks Larrin.

I want to note, however, that I'm very intentionally not considering cutting ability in these tests, at least as how I understand Catra testing works. I don't regrind knives, and I don't normally bother to do microbevels, so for my uses I am trying to only look at what wear occurs at the very apex for a better comparison between knives. I'm making no consideration for how much force it takes to cut things, like Ankerson or Cliff Stamp do, as then I'm just comparing too many things at once. Those are important considerations, to be sure, but it's not something I'm interested in getting into.

You’re lucky Cliff is banned so he can’t disagree with you about only testing cutting ability and not sharpness.

 

[marrenmiller]

You’re lucky Cliff is banned so he can’t disagree with you about only testing cutting ability and not sharpness.

I'll change my tune when I see convincing tests showing that two otherwise identical knives with different edge thicknesses would have different edge retention. I saw Cliff had written that but the testing he referenced was with different knives by different makers at different edge thicknesses...

 

[kylemiller]

I've never believed that edge thickness affects edge retention, but rather cutting ability. This is a long video but this individual tests exactly this assertion.

Tl;Dw: edge thickness being varied between two otherwise identical knives resulted in the same edge retention.

Well just like the videos that show M390 vastly outperforming S30V etc., this is also a case of my experiences differing from people's testing.

I think it depends how you define a cut, right? Are we talking about a clean laceration or just separating matter? If so I'll take a dull Delica over a dull 0562. I find when a knife is very thin BTE I'm cutting with the whole blade (or at least more of it) rather than just the secondary bevel, which is how I felt cutting with a lot of ZT offering's and some of the chubbier Hinderer's.

Take a Spyderco Smock. Dumb thin behind the edge. Give me that in AUS-8 over a 0562 in 20CV any day of the week if I have a stack of cutting to do. I believe after the same amount of material cut the Smock is going to do a better job cleanly separating matter.

Maybe I'm sharpening wrong or judging sharpness in a different way, but geometry has always been the biggest variable in how long my blades stay at the level of sharpness I like them to be.

 

[marrenmiller]

Well just like the videos that show M390 vastly outperforming S30V etc., this is also a case of my experiences differing from people's testing.

I think it depends how you define a cut, right? Are we talking about a clean laceration or just separating matter? If so I'll take a dull Delica over a dull 0562. I find when a knife is very thin BTE I'm cutting with the whole blade (or at least more of it) rather than just the secondary bevel, which is how I felt cutting with a lot of ZT offering's and some of the chubbier Hinderer's.

Take a Spyderco Smock. Dumb thin behind the edge. Give me that in AUS-8 over a 0562 in 20CV any day of the week if I have a stack of cutting to do. I believe after the same amount of material cut the Smock is going to do a better job cleanly separating matter.

Maybe I'm sharpening wrong or judging sharpness in a different way, but geometry has always been the biggest variable in how long my blades stay at the level of sharpness I like them to be.

That channel is actually notable for constantly finding M390 to perform poorly, and essentially equivalent to S30V/S35VN/XHP in most cases. I wouldn't write off what he's saying without taking a look first.

We're just talking about different things here, that's all. Edge retention =/= cutting ability. I am on the same page as you that I'd rather have a dull Delica than any dull ZT for actual cutting, as the Delica will have better cutting ability than the ZT with the same edge. You're entirely right that a thinner grind will make separating material easier, but that's referring to cutting ability, not edge retention. The actual edge of the Spyderco may or may not hold up as well as the edge on the ZT, but its superior cutting ability might still have it perform better for you. Unfortunately, to test cutting ability objectively is a tricky task (requires precisely measuring force), and I'd rather leave that up to a machine.

With what I'm doing, in theory I'm only concerned about the very apex of the edge making cuts in very thin materials like hair or paper. If you want to think of it this way, I'm only using the cardboard to help dull the edge quickly and somewhat repeatedly until it stops cutting those thin materials. I'm not attempting to measure how easily the cardboard is cut. I'm really trying to see how the steel is heat treated and how well it holds a given edge without getting into the overall geometry of the knife. Hope that helps.

 

[Larrin]

I wouldn’t say that cutting ability can necessarily be easily separated from sharpness. For example, if the thicker knife requires more force to cut through the material then that would be expected to affect the evolution of sharpness. That may be true whether it is differences in behind the edge thickness or edge angle. Of course with different edge angles that would also change how the apex dulls.

 

[me2]

Edge thickness can become important in tests using a cutting board like many people used to for rope cutting. At the end of the cut, thicker edges get bumped I to the cutting board harder than thinner ones. Edge thickness is also important when considering lateral loads. If everything is perfectly lined up, no lateral loads are significant. However, they never are lined up that way. A great deal of dulling comes from lateral deformation. For that, thickness behind the edge and cutting ability matter in edge holding.

I did testing like this for many years. I answered the questions I wanted to answer and basically don't do it any more. Three tests are instrumental in what I found. I tested a $10 kitchen knife on cardboard and it was still paper cutting sharp after 3500 feet. Not printer paper slicing, but thinner notebook paper. I could fold a piece in half, stand it vertically on a table and cut it with a single swipe.

I tested a knife made from annealed 1095. It did surprisingly well. That was a test cutting cardboard and then push cutting thread on a scale to test sharpness, similar to the BESS testers used now. I cut a few dozen feet before the annealed blade was obviously behind the others.

Finally I tested a S110V blade against a CTS BD1 blade during a garage clean up. Side by side, dividing each task between the 2 blades, edges sharpened to the same angle and grit finish and the thickness behind the edge within a few thousandths of an inch. The next weekend I repeated it. No discernable difference between the 2. I sold the S110V blade and use the BD1 blade as an EDC knife.

The combination of edge angle, edge thickness, and (here's a new one for you) grit finish overshadow steel choice as long as the blades are hardened. I buy knives based on design and features now, not steel. If steel is an option I get the steel I think can take the shallowest edge angle and is the easiest to sharpen. My current EDC knife is a reground Delica with VG10 steel. When the edge thickness gets above 0.025" I'll regrind it again, but thinner than last time. It was 0.015 after regrinding, on top of a 12 degree per side (dps) edge angle, with a 15 dps microbevel from the Spyderco Sharpmaker medium grit triangles.

 

[Natlek]

What do you think about this test ?

 

[Natlek]

This is used circular saw for granite .....HOW they cut granite ? Diamond are embeded in bronze / ? / randomly .When saw spin EVERY single diamond exposed on sutface cut chanel in granite and make room for steel behind diamond inserts .... When matrix around diamond get worn diamond will fall under forces and new one will come on surface .Without diamonds saw is totaly useless , right ? Now , more diamond on surface better/faster cutting .But there must be are limit ............???? If they use to much diamond they will fall more easy from bronze matrix.I mean if two diamond touch each one there was less bronze to hold them in place so less force is needed to pull them from matrix ?
About steel ....it is imposible steel with LESS carbide content /same type/ to OUTPERFORM or to have equal edge retention with steel which have twice more carbide ....
tungsten carbide outperform HSS steel , HSS steel outperform carbon tool steel.......no question about that .Push cut make almost no use of carbides ,slicing motion make use of carbides .Are carbide exposed on edge or they are cut in level with matrix? That make difference ...........

 

[Natlek]

Have you tested any knives with identical steel, heat treat, edge angle, etc. where the only difference between tests was the edge thickness?

I can make test like that .I have several knife /cut from same HSS circular saw / with different edge thickness .But it will be problem to find enough cardboard ...I asume that all cardborad should be same , to ?

 

[marrenmiller]

I wouldn’t say that cutting ability can necessarily be easily separated from sharpness. For example, if the thicker knife requires more force to cut through the material then that would be expected to affect the evolution of sharpness. That may be true whether it is differences in behind the edge thickness or edge angle. Of course with different edge angles that would also change how the apex dulls.

That appears to be a commonly held belief but I see no physical process by which the apex of an edge would see more load due to more obtuse edge geometry behind it (at a given edge angle, to be clear), nor any tests confirming it. It seems like a poorly considered argument that more force to cut = more degradation on the edge. It ignores any consideration of what parts of the knife contribute to the increased difficulty of cutting, and assumes that that increased load must be evenly distributed on the entire knife. I would think that a simple summation of forces on the body being considered would indicate that to be clearly inaccurate.

As a thought, if I took a given knife and glued a large flange to the spine of it, making it drag quite a bit more, would you think that would affect in any way what loads are on the edge? I would suggest the added drag is going to be mostly on the flange, depending on how the cardboard now contacts the knife, and unless there's some interaction between how the flange makes the cardboard split at the edge, then there's no reason it would have an effect on the edge. If anything, one could envision the flange acting to force the cardboard apart and letting the edge fall into a cut which is under tension. I'm not suggesting the flange would increase edge retention here, but my point is there needs to be some explanation or conclusive demonstration that more obtuse edge geometry above the apex results in more wear at the apex.

Maybe someday someone will do a study on it?

 

[marrenmiller]

Edge thickness can become important in tests using a cutting board like many people used to for rope cutting. At the end of the cut, thicker edges get bumped I to the cutting board harder than thinner ones. Edge thickness is also important when considering lateral loads. If everything is perfectly lined up, no lateral loads are significant. However, they never are lined up that way. A great deal of dulling comes from lateral deformation. For that, thickness behind the edge and cutting ability matter in edge holding.

That's a good physical explanation for why there'd be a greater dulling effect to a thicker edged knife. That being said, I'm not pushing a knife into a cutting surface hardly at all in my tests (it's just a soft cardboard stop to prevent me from hitting the ground, but usually I don't touch it at all), nor is a Catra machine doing so, and IMO slamming into a hard wooden surface is something that should be avoided in a controlled test unless that's specifically how you cut things. I sure don't.

The combination of edge angle, edge thickness, and (here's a new one for you) grit finish overshadow steel choice as long as the blades are hardened.

Agreed on that. I'm only keeping 600 grit diamond plate for some conformity to other testers, who seem to settle on DMT fine stones and a ~0.1m diamond finish strop. I think better results could be obtained with different finishes, to say nothing of the other factors.

 

[sodak]

I got into some testing about 10 or 15 years ago, published some of my findings. Then life with family and children forced me to quit, now that they are in college, I might start up again.

Some of the things I learned are:

1. Testing takes a LOT of time, and there are far more variables to control than you would guess at first.
2. My results sometimes line up with others, sometimes don't. I have some tests that have agreed with Ankerson's and Me2's, some that don't. After watching Ankerson on youtube, I realized that he cuts rope completely differently than I do, that could also be a variable. In short, I find when other testers contradict my findings, I learn a TON more by digging into those differences than by tests that we agree on. When other testers disagree with your results, that's a GOOD thing, there's learning to be had.
3. Constructive criticism is very valuable, but... (see number 4).
4. The general public, even on BF, is extremely ungrateful. You post your results, there will be a lot of people willing to tell you how you got it all wrong, and tell you to do a bunch of it all over again changing, this, that, and the other thing. You can either tell them to pound sand, or duplicate your tests with their desires. They then fade away very quickly because they instinctively know how much work it requires.
5. You test a steel from a popular company or maker that doesn't do well, the fanboys will flame you incessantly. Personally, I tell them to pound sand then add them to my ignore list, but it might bother you. Be prepared for that.
6. There is something to be learned from every test made. Always thank someone for trying.

That's it for me. You would think that a chunk of hardened steel isn't that difficult or mysterious. I think that someone could spend a lifetime on just one steel testing heat treatments and properties, and we would only scratch the surface.

 

[DeadboxHero]

That appears to be a commonly held belief but I see no physical process by which the apex of an edge would see more load due to more obtuse edge geometry behind it (at a given edge angle, to be clear), nor any tests confirming it. It seems like a poorly considered argument that more force to cut = more degradation on the edge. It ignores any consideration of what parts of the knife contribute to the increased difficulty of cutting, and assumes that that increased load must be evenly distributed on the entire knife. I would think that a simple summation of forces on the body being considered would indicate that to be clearly inaccurate.

As a thought, if I took a given knife and glued a large flange to the spine of it, making it drag quite a bit more, would you think that would affect in any way what loads are on the edge? I would suggest the added drag is going to be mostly on the flange, depending on how the cardboard now contacts the knife, and unless there's some interaction between how the flange makes the cardboard split at the edge, then there's no reason it would have an effect on the edge. If anything, one could envision the flange acting to force the cardboard apart and letting the edge fall into a cut which is under tension. I'm not suggesting the flange would increase edge retention here, but my point is there needs to be some explanation or conclusive demonstration that more obtuse edge geometry above the apex results in more wear at the apex.

Maybe someday someone will do a study on it?

Spine? If you're going test your behind the edge theory than your flange has to be at the shoulder of the edge bevel not the spine.