Stable edge steels (NOT TOUGHNESS)

[Ankerson]

Apparently when you push on the edge and stress the steel it is going to fail. If it is a brittle steel it will chip, if it is a tough steel then it will roll. But either way you exceed the steel's limit and it fails. If you want a more stable edge then you need a stronger steel, raise that limit. A stronger steel is a steel with higher hardness. So the most stable edge will probably be the steel that you can harden the most.

Actually if a steel chips all that means is that the limits have been exceeded for the edge, HT etc....

That's given a correct HT in the 1st place.

There are no brittle steels that have been HTed correctly for the purpose at hand.

Any steel can chip or roll depending on the HT etc.

[Drebs]

Resistance to deformation is measured by hardness (not controlled by steel but by heat treatment). Resistance to chipping is measured by toughness. So asking which is the most stable but without toughness doesn't make any sense. An edge which loses cutting ability to either chipping or rolling is still not cutting as well. The edge has to have a more obtuse angle to make up for lower hardness and/or toughness.

So I know your not one to tip your hat but what common steels are at the greatest intersection of these two roads in common use? I quite interested in 4v vs rex 45 vs cruwear vs 52100 vs k390vs m4. In terms of edge stability, meaning on my m390 I don’t know what in the world I do I understand what a knife is and what I tool is and how to “use” a knife properly but my edge would say otherwise.

So in shawns Rex 45 vs m4 video trying to chip the edge on brass. We know the Rex 45 is harder but the m4 might be tougher ( maybe I’m wrong but I thought toughness was resistance to shattering shear lateral force before breaking) because it’s not a brittle. However Rex 45 beats the m4 in edge stability in that video does that mean it’s both harder and tougher ? Does it mean cruwear at less hardness but more toughness theoretically could or feasibly would have the same edge stability ? So in essence if we make up values to 100 for “edge stability” and Rex has 70 hrc and 30 toughness equaling “100” units of “edge stability” cruwear could have 65 toughness and 35 hrc and at the end of the day have the same “edge stability”.

This got hid a ways back due to time lapse on moderator approval but this last paragraph is what I’m wrestling with have been reading knifesteelnerds articles I’m wresting with understanding this...

[Albatross]

Resistance to deformation is measured by hardness (not controlled by steel but by heat treatment). Resistance to chipping is measured by toughness. So asking which is the most stable but without toughness doesn't make any sense. An edge which loses cutting ability to either chipping or rolling is still not cutting as well. The edge has to have a more obtuse angle to make up for lower hardness and/or toughness.

So I know your not one to tip your hat but what common steels are at the greatest intersection of these two roads in common use? I quite interested in 4v vs rex 45 vs cruwear vs 52100 vs k390vs m4. In terms of edge stability, meaning on my m390 I don’t know what in the world I do I understand what a knife is and what I tool is and how to “use” a knife properly but my edge would say otherwise.

So in shawns Rex 45 vs m4 video trying to chip the edge on brass. We know the Rex 45 is harder but the m4 might be tougher ( maybe I’m wrong but I thought toughness was resistance to shattering shear lateral force before breaking) because it’s not a brittle. However Rex 45 beats the m4 in edge stability in that video does that mean it’s both harder and tougher ? Does it mean cruwear at less hardness but more toughness theoretically could or feasibly would have the same edge stability ? So in essence if we make up values to 100 for “edge stability” and Rex has 70 hrc and 30 toughness equaling “100” units of “edge stability” cruwear could have 65 toughness and 35 hrc and at the end of the day have the same “edge stability”.

This got hid a ways back due to time lapse on moderator approval but this last paragraph is what I’m wrestling with have been reading knifesteelnerds articles I’m wresting with understanding this...

According to the datasheets, Rex 45 is surprisingly less tough than CPM M4.

With the testing I've seen done on Spyderco blades, CPM Cruwear rolls well before Rex 45 will roll or chip.

Cruwear has more toughness, but it lacks the hardness needed to have the edge stability of Rex 45. Also, if you lower the hardness to 35 HRC, you'll lose all edge retention and have an edge that rolls where even low end steels won't.

[Abyss_Fish]

I know there’s a lot of talk in here about hyper tough carbon steels. But I’ve been using and abusing knives in lc200n for close to a year now, and they have some incredible edge stability. The ONLY time I had lc200n chip out on me was when the sharp corner of a Ti lanyard bead was bashed into the factory edge on my waterway. Otherwise I have never had it chip. It’s a ridiculously well balanced steel.

Lc200n has toughness just above 1095, edge retention just above s30v, and ductility on par with 3V. While being impervious to pitting or rusting. Glorious stuff.


Plus an honorable mention to sg2/r2, I’ve abused multiple knives in that stuff at work almost daily for the last 6 months. No chips at all.

[Drebs]

Resistance to deformation is measured by hardness (not controlled by steel but by heat treatment). Resistance to chipping is measured by toughness. So asking which is the most stable but without toughness doesn't make any sense. An edge which loses cutting ability to either chipping or rolling is still not cutting as well. The edge has to have a more obtuse angle to make up for lower hardness and/or toughness.

So I know your not one to tip your hat but what common steels are at the greatest intersection of these two roads in common use? I quite interested in 4v vs rex 45 vs cruwear vs 52100 vs k390vs m4. In terms of edge stability, meaning on my m390 I don’t know what in the world I do I understand what a knife is and what I tool is and how to “use” a knife properly but my edge would say otherwise.

So in shawns Rex 45 vs m4 video trying to chip the edge on brass. We know the Rex 45 is harder but the m4 might be tougher ( maybe I’m wrong but I thought toughness was resistance to shattering shear lateral force before breaking) because it’s not a brittle. However Rex 45 beats the m4 in edge stability in that video does that mean it’s both harder and tougher ? Does it mean cruwear at less hardness but more toughness theoretically could or feasibly would have the same edge stability ? So in essence if we make up values to 100 for “edge stability” and Rex has 70 hrc and 30 toughness equaling “100” units of “edge stability” cruwear could have 65 toughness and 35 hrc and at the end of the day have the same “edge stability”.

This got hid a ways back due to time lapse on moderator approval but this last paragraph is what I’m wrestling with have been reading knifesteelnerds articles I’m wresting with understanding this...

According to the datasheets, Rex 45 is surprisingly less tough than CPM M4.

With the testing I've seen done on Spyderco blades, CPM Cruwear rolls well before Rex 45 will roll or chip.

Cruwear has more toughness, but it lacks the hardness needed to have the edge stability of Rex 45. Also, if you lower the hardness to 35 HRC, you'll lose all edge retention and have an edge that rolls where even low end steels won't.

Yeh sorry I didn’t mean 35 hrc I was just making up nominal values in change percentage wise. Just purely hypothetical the numbers didn’t represent anything real but “magical percentage changes”.

Well I agree with you about cruwear and rex 45 that’s where I’m confused by larrins explanation explaining that “Resistance to chipping is measured by toughness”. However I suppose rex is “tough enough” not to chip and while cruwear is tougher it won’t break as easy due to lateral force, however it’s lack or hrc lends it to roll. So back to my main topic of this post what steel has the most edge stability IN NORMAL USE, not batoning prying , maybe the occasional lateral zip tie twist cut at stock it seems to me based on my point of view to be rex 45. Lc200n seems to also be one that I’ve had my eye on that gets overlooked. In pure edge stability apples to apples in normal knife uses with occasional pushing it I don’t seem anything that can challenge rex 45 IN A SPYDERCO AT THE HRC SPYDERCO RUNS THE STEELS IN QUESTION AT. Again maybe k390, maybe 52100? But seems to be the same hrc as cruwear, maybe a tighter grain structure? Larrins charts do show 52100 maybe a hair tougher than cruwear at the same hrc. I very rarely make blanket statements but I’ve had so many different Spyderco steels but after looking at all the cut test, all larrins info, all the Anecdotal results and evidence out there I don’t see any advantage to carbon steel Spyderco in the pm2, pm3, manix, shaman family over rex 45 for one anyone who’s into the details and wants a “extraordinary” steel with both amazing and seldom seen edge stability and edge retention. I get some guys run s30v or 440’s and are doing great. Short of corrosion which in that case I have S90v and lc200n I’m really seeing no reason for anything else IN A FOLDER. Unless you like easier touch ups or field sharpening.

Just one guys opinion not trying to be controversial but would love another point of view someone we get pigeonholed into our own view and get tunnel vision based on metrics we focus on to much so I would love to have my perspective challenged wouldn’t be the first time I was humbled. There is power in council wisdom.

Cheers, Drew

[Baron Mind]

Edge stability is controlled mainly by edge geometry, but following that is is grain structure (finer is better), carbide volume (lower is better), carbide size(smaller is better) , and hardness (higher is better, though all steels have a point where they become too brittle).

[Drebs]

Edge stability is controlled mainly by edge geometry, but following that is is grain structure (finer is better), carbide volume (lower is better), carbide size(smaller is better) , and hardness (higher is better, though all steels have a point where they become too brittle).

Great things to remember and be reminded of.

https://youtu.be/WOpu13O_OFE

This is the video that made me fall in love with Rex-45 from deadboxhero in here, big brown bear on YouTube, triplebhandmade on insta, Shawn in real life, one of the more influential knife guys pushing things and playing with new steels he knows his stuff

Do you know of any charts for grain structure that assigns it a value or quantifies then In their “fineness” in some way ? The only place I know to see is knife steel nerds and look at the graphs, however sometimes I interpret them wrong.

[bdblue]

For comparing failure behavior of different steels you still have to keep in mind the strength of the steel after heat treat.

My previous post stated the relationships but maybe I was too simplistic with the wording.
Exert stress on steel and it deforms. Up to its elastic limit is deforms elastically, we would think of it acting like a spring. When the elastic limit is reached, then the steel deforms plastically. If it is tough steel it deforms more, if it is a less tough steel then it fractures before it has deformed very far. I'm sure we've all bent a piece of steel wire, maybe a coathanger. Mild steel like that really exhibits the bilinear stress-strain behavior. Much stronger steels barely have something resembling the second line, think of the behavior of a piece of glass. It deforms elastically up to its elastic limit, then it fractures. This would represent the ultimate in non-ductile steels.

HRC is a measure of strength, somewhat representing the elastic limit mentioned above. So a ductile steel that has a lower elastic limit will reach its elastic limit and roll before a brittle steel that has a higher elastic limit would reach its limit and fracture. Maxamet for instance has like zero toughness but can become so hard that it has some usable edge stability. Rex45, if it turns out to have lower toughness than M4, can go farther before chipping because it is stronger, has higher elastic limit, or HRC if you prefer.

People get too confused with respect to the concept of toughness by the way toughness is measured. I believe this was just a convenient way to test it that someone devised back in history even though they were primarily interested in a static property of the material. You should see the way some of the properties of soils are measured.

[JohnDoe99]

If you want something that doesn't roll, then pretty much everything at or beyond S30V from Spyderco will do.

[GarageBoy]

You should see the way some of the properties of soils are measured.

Geotechnical engineer?

Deadboxhero's video probably has probably sold more rex45 than anything else

Someone should do a video explaining impact toughness vs edge strength

[Albatross]

You should see the way some of the properties of soils are measured.

Geotechnical engineer?

Deadboxhero's video probably has probably sold more rex45 than anything else

Someone should do a video explaining impact toughness vs edge strength

I believe he's mentioned the differences in at least one of his videos.

[Karl_H]

Larrin provides a very thorough explanation of toughness and chipping in this article: https://knifesteelnerds.com/2018/05/28/ ... -of-edges/

If you really want a deep understanding of edge stability, it is worth your time to read all of Larrin’s online articles on this subject or read his book.

[Drebs]

You should see the way some of the properties of soils are measured.

Geotechnical engineer?

Deadboxhero's video probably has probably sold more rex45 than anything else

Someone should do a video explaining impact toughness vs edge strength

That last sentence makes a lot of sense... in shawns video he’s torquing the edge against brass (pure edge stability) impact would be cutting through cardboard coming out the back side and hitting the brass rod fast and hard? Both are examples of edge stability and not interchangeable but independent types of edge stability ?

[bdblue]

You should see the way some of the properties of soils are measured.

Geotechnical engineer?

I'm a structural engineer, we interface with geotechnical engineers and we take geotechnical courses in college.

Larrin provides a very thorough explanation of toughness and chipping in this article: https://knifesteelnerds.com/2018/05/28/ ... -of-edges/

I haven't had time to do more than skim the article but it is interesting to see a knife person talk about stress-strain curves and fracture mechanics. Stress-strain is one of the first things we study in college and I took a course in fracture mechanics in grad school.

[GarageBoy]

Hey, another fellow engineer in the buildings trade

I'm definitely picking up larrin's book at some point - materials science classes were my favorite