1095 vs cpm-3v: Same toughness, increased cutting performance?

[ocnLogan]

Ok, so just to start this off, know that I have searched around a bit, and have some basic knowledge. For instance, I know that CPM-3v is much tougher, has better wear resistance, and is even more resistant to corrosion. That much I'm familiar with. What I'm more interested in is the "so what" of the details and differences between steels.

So when I first started learning about knives and the differences between steels a few years ago, one of the reasons for "higher end" steels that was supposedly that you could make either (or both) the primary grind, or the secondary grind much thinner, resulting in better cutting performance with the "same" toughness/reliability of the blade.

I've been thinking of getting a 4in - 4.5in fixed blade (Becker BK16 is the highest on the list) to be my main belt knife while camping. The uses of this knife would be basically everything from food prep, to feathersticks, to "reasonable to respect to blade length" light batoning. By that I mean... 2-3in max (making sure its straight grained), just breaking things down for the fire (mostly to get a good solid feather stick going). For those concerned, a folding saw, and a larger blade (bk9, as I usually car camp with my wife). This belt knife would take the place of mora that I'm using right now.

And while the Becker isn't "expensive", it becomes more expensive if you add micarta, and a different sheath. The BK16 is 5/32in thick, and is a FFG. I know that it is going to be plenty strong enough for sensible usage of the blade. After looking at the knifemakers forum, it appears that a custom might not be "that" much more expensive (seen 1095 blades in this range sold with sheaths and handles as low as $65 recently) than a BK16, which got me thinking.

The question

What I'm asking is simple. Does the extra toughness of a better steel like CPM-3V enable a maker to make something (for the sake of discussion, we'll say we're comparing it to the blade shape and 1095 cro-van of the Becker BK16) out of thinner blade stock to improve cutting/slicing performance while retaining essentially the same overall strength? Am I way underthinking this?

Can you take that BK16-ish blade shape and whatever its "toughness" is at 5/32in thick and FFG, and make it in say... 1/8in CPM-3V and make it the "same" toughness, and have it be even slicier?

And on the topic of customs, how common is it to have a maker sell you just the ground blank (ready for scales, with holes drilled, primary and secondary grinds done) without a sheath or scales? Does that really lower the cost much? I've done two sets of my own Blue-Jean Micarta, and feel "relatively" comfortable making/shaping it. I've also considered trying my hand at sheathmaking, so building from a blank done by someone else seems like a natural progression.

Anyway, thanks for the help everyone .

 

[ocnLogan]

Bump.

Is there another place I should be asking this, or does the question just not make any sense?

 

[K.O.D.]

Ka-Bar/Becker's 1095 Cro-Van is not actually 1095. Its 1095 with chromium and vanadium added, which makes it another beast entirely.

Other than that, I think its makers preference, availability and cost of the particular steel.

Your question would be best answered in the knifemaker's sub forum.

 

[james terrio]

Does the extra toughness of a better steel like CPM-3V enable a maker to make something (for the sake of discussion, we'll say we're comparing it to the blade shape and 1095 cro-van of the Becker BK16) out of thinner blade stock to improve cutting/slicing performance while retaining essentially the same overall strength?

The short answer is, "yes". But spine thickness in this case is not as big a factor as it may seem.

The real differences, especially comparing a relatively small/medium blades like the 16, isn't so much in the raw toughness of a 5/32" bar of 1095CV vs. a 1/8" bar of 3V, which are going to be pretty similar and give you very nearly the same overall bevel angles with a FFG... we're talking fractions of, or maybe a degree or two difference.

The improved performance potential comes from the fact that you can grind the edge thinner before sharpening (perhaps .005" on 3V vs. .010" or .015"+ on typical 1095 factory blades) and sharpen it more acutely, and HT it at a much higher hardness (say 3V at 60Rc instead of 1095 @ 56Rc) while retaining the same or better toughness, and enjoy both more "sliciness" and the edge-retention advantage of harder steel with more fine carbides in it.

In other words, the big advantage of 3V isn't so much that it's way tougher than 1095, it's that it retains that toughness at higher hardnesses and across thinner sections.

Of course a skilled maker can achieve some of the same sort of improvements using the same steel - factory blades are generally HT'ed fairly soft and ground fairly thick, just because it's cheaper that way and results in a more "idiot proof" knife.

 

[ocnLogan]

Thank you James, that is exactly what I was looking for. So it is not just the overall thickness of the bar stock that makes the difference, it is instead the same concept that I was talking about, but for the thickness behind the secondary grind (at least for the "slicey-ness").

And last question I have that is related to this is just if there is any idea how much thinner a 3v could be while retaining similar overall strength? I just used 1/8in as an example, but could 3/32 work?

And again, thank you for your answer, I really appreciate it.

 

[chiral.grolim]

CPM-3V is ~2X tougher than 1095 via notched Charpy (impact toughness) @ 57-58 Rc. One might infer that CPM-3V could then be made 2x thinner than 1095 and retain the same toughness, but the Charpy values are based on a standardized sample, it may not be (indeed probably not) a linear change as the sample is reduced to a much thinner cross-section or much different shape (blade vs bar). Usually knife-toughness matters at the very edge where chips lead to dullness or even catastrophic failure.

Anyway, the reason for increased edge-thickness may be increased toughness against impact (more material support to prevent large chips) but increased spine-thickness is more for strength against lateral stress, i.e. prying, especially for a knife as small as the BK-16. Lateral-strength depends on the steel matrix and final hardness. A harder material is more resistant to deformation than a softer material. CPM-3V can be made harder than 1095 (i.e. stronger) while retaining the same toughness. But that doesn't mean it won't bend, just that it won't permanently deform as readily. Stiffness, i.e. resistance to bending, comes from the material's thickness and is cubically proportional to thickness. What this means is that from 1/16" to 2/16" (2-fold increase) comes 8X more stiffness, i.e. it requires 8X the force to induce the same amount of lateral flex against the blade.

In summary, a thinner knife (spine as well as edge) is much more 'slicy' but much easier to bend (elastically), not so good for prying. A thicker knife won't bend as easily under stress, but also won't penetrate as deep on a cut. How much stiffness do you need? How 'slicy'? In either case, CPM-3V can retain the same level of toughness as 1095 but at higher hardness which lends strength to the very edge so it neither chips nor blunts/rolls as easily. You may be able to make it 2X thinner behind the edge and retain that toughness. But if you make it 2X thinner at the spine, you'll notice that it flexes more easily against lateral stress.

 

[james terrio]

And last question I have that is related to this is just if there is any idea how much thinner a 3v could be while retaining similar overall strength? I just used 1/8in as an example, but could 3/32 work?

Depends what you mean by "work". It would be a very different knife, regardless of steel selection. If you like the BK-16 for the purposes for which it was designed, making it that much thinner would take away a lot of what makes it a very good design - namely that it's ground acutely enough to cut well, but it's thick and sturdy enough that it can still take some pretty aggressive use.

See Chiral Grolim's post above. It gets a little complicated when trying to change factors by large amounts, especially comparing two very different steels. Toughness/strength/flexibility are three different characteristics... yet they often tend to all work together. That's what's so great about 3V... the high toughness and high strength makes it what I call a "well balanced" steel. Grind it thin enough and it's just as flexible as any other blade steel with the same geometry (say if you wanted a delicate bendy filet knife with high edge-retention... 3V works nicely for that, as well as big beefy choppers).

Dropping from 5/32" all the way down to 3/32" stock would have a significant impact on the blade's flexibility, general toughness (resistance to just breaking) and overall strength (resistance to being deformed). I haven't done the actual math but off the top of my head, that's something like a 40% reduction in the total mass of the blade once it's ground... that's a lot. More steel is more stronger/tougher overall, there's no getting around that.

 

[ocnLogan]

Wow, this is super informative. Thank you BOTH very much, as I understand I'm being a bit particular here as I'm trying to make sure I understand the moving parts. You've both done a very good job of explaining it.

And for the record, while I do some things (like baton what I consider to be reasonably sized and grained wood) that might be "abusive" to my knives, prying isn't one of the things that I do with knives. I'm also not at all above splitting a small wedge off of a larger piece to finish the splitting for me. I've never once even started to bend even my Mora (although back when I first was getting my feet under me in this hobby, I did bend a Kabar ZK War Sword pretty good in a knot).

Anyway, back to the topic at hand.

So the toughness factor mainly comes down to how thick the shoulders of the secondary grind can be left and still be reliable (not chip, deform, etc) under its expected use. Spine thickness then helps determine the overall lateral strength of the blade. And so if I'm reading this correctly, this helps not only with things like prying, but with things like not deforming while say... battoning through something? I'm assuming that the strength then is related to the cross sectional area/volume of material in the knife. This would then be why saber ground knives are stronger, and hollow ground ones are weaker (although that might be because the amount behind the edge). Am I understanding that right? Or is it just straight up spine thickness?

And when I say "would it work", I was meaning that more or less, the knife could be used in exactly the same way. That if we could objectively measure strength, and impact resistance, and all of those other things, if it would remain more or less the same as the BK16. With the improvement of the steel allowing for better "more slicey" performance. It appears that I was confused about "toughness" and "strength" though, as the toughness might indeed be the same at "some" thinner blade stock thickness, the strength seems it will be almost always lower.

 

[rustyrazor]

Great Post! I didn't know the math on how much more rigid and whatnot... awesome info guys. i would comment about how i see the "saber grind/flat grind/hollow grind" issue, but i'm gonna sit back and let you fellas explain this way better than i ever could... Damn math! lol keep it coming

 

[Ankerson]

Ok, so just to start this off, know that I have searched around a bit, and have some basic knowledge. For instance, I know that CPM-3v is much tougher, has better wear resistance, and is even more resistant to corrosion. That much I'm familiar with. What I'm more interested in is the "so what" of the details and differences between steels.

So when I first started learning about knives and the differences between steels a few years ago, one of the reasons for "higher end" steels that was supposedly that you could make either (or both) the primary grind, or the secondary grind much thinner, resulting in better cutting performance with the "same" toughness/reliability of the blade.

I've been thinking of getting a 4in - 4.5in fixed blade (Becker BK16 is the highest on the list) to be my main belt knife while camping. The uses of this knife would be basically everything from food prep, to feathersticks, to "reasonable to respect to blade length" light batoning. By that I mean... 2-3in max (making sure its straight grained), just breaking things down for the fire (mostly to get a good solid feather stick going). For those concerned, a folding saw, and a larger blade (bk9, as I usually car camp with my wife). This belt knife would take the place of mora that I'm using right now.

And while the Becker isn't "expensive", it becomes more expensive if you add micarta, and a different sheath. The BK16 is 5/32in thick, and is a FFG. I know that it is going to be plenty strong enough for sensible usage of the blade. After looking at the knifemakers forum, it appears that a custom might not be "that" much more expensive (seen 1095 blades in this range sold with sheaths and handles as low as $65 recently) than a BK16, which got me thinking.

The question

What I'm asking is simple. Does the extra toughness of a better steel like CPM-3V enable a maker to make something (for the sake of discussion, we'll say we're comparing it to the blade shape and 1095 cro-van of the Becker BK16) out of thinner blade stock to improve cutting/slicing performance while retaining essentially the same overall strength? Am I way underthinking this?

Can you take that BK16-ish blade shape and whatever its "toughness" is at 5/32in thick and FFG, and make it in say... 1/8in CPM-3V and make it the "same" toughness, and have it be even slicier?

And on the topic of customs, how common is it to have a maker sell you just the ground blank (ready for scales, with holes drilled, primary and secondary grinds done) without a sheath or scales? Does that really lower the cost much? I've done two sets of my own Blue-Jean Micarta, and feel "relatively" comfortable making/shaping it. I've also considered trying my hand at sheathmaking, so building from a blank done by someone else seems like a natural progression.

Anyway, thanks for the help everyone .

It actually sounds like you are talking about two different knives here....

You want a 4"- 5" thin slicer that holds an edge and cuts really well......

AND

You want a knife that you can baton with....... Even light batoning is still batoning.....


All this when you stated you already have an ax, saw, and a large fixed blade.....

So the real question is why would you be doing any batoning at all or even anything more than making fuzzy sticks at the MOST with the purposed small slicer?

Personally I think you need to really decide what you want...

 

[ocnLogan]

It actually sounds like you are talking about two different knives here....

You want a 4"- 5" thin slicer that holds an edge and cuts really well......

AND

You want a knife that you can baton with....... Even light batoning is still batoning.....


All this when you stated you already have an ax, saw, and a large fixed blade.....

So the real question is why would you be doing any batoning at all or even anything more than making fuzzy sticks at the MOST with the purposed small slicer?

Personally I think you need to really decide what you want...

Well, the original question was how much more "slicey" I could get a moderately sized knife, with a strength and toughness that still roughly equaled a BK16 (which I consider more than robust enough). The question was just as much about if it was possible, as well as the specifics that we've talked about. I just was unsure if the benefits of better steel could take something I already think highly of, and make it perform better without sacrificing any strength/toughness.

The only use case that I could think of for batoning with this theoretical knife is if I was somehow out camping/hiking, and got separated from everything else that I have with me (as this will be the one on my belt, instead of in a bag/pack). I would still like to have the option to use that skill in some degree if the need presented itself. But as it is right now, the saw cuts, the BK9 splits anything that needs splitting, and the mora feathersticks and does normal camp chores (tent pegs, some food stuff, etc), and I was thinking that a FFG blade might do better as an all arounder to replace the mora.

But you're right, perhaps I need to sort out more what I'm looking for, as its possible that this idea isn't feasible/worth it/thought out well enough. I am still learning about myself, my skills, and what I feel comfortable with. That, and I really found what those are more knowledgeable have helped me learn, so perhaps its not a total waste.

And I didn't say I had an axe (but the other things are spot on).

 

[james terrio]

Without getting into a whole bunch of math that I'm frankly too lazy and dumb to muddle through, yeah you're on the right track. 3V is both tougher and stronger than 1095 at the same hardness, with the same geometry. Exactly how that breaks down regarding... how much thinner 3V stock can you use to reduce mass without going below the toughness/strength of 1095 at given thickness... I don't know.

The answer to designing a knife is really to decide first on the geometry you want to start with. Geometry is what cuts, and thinner cuts better. THEN worry about alloy selection and HT to suit your needs.

Or.... just use 3V and have it ground any dang way you want -from a big honkin' chopper to a fine little slicer - and have a great deal of confidence in it regardless

 

[Ankerson]

Well, the original question was how much more "slicey" I could get a moderately sized knife, with a strength and toughness that still roughly equaled a BK16 (which I consider more than robust enough). The question was just as much about if it was possible, as well as the specifics that we've talked about. I just was unsure if the benefits of better steel could take something I already think highly of, and make it perform better without sacrificing any strength/toughness.

The only use case that I could think of for batoning with this theoretical knife is if I was somehow out camping/hiking, and got separated from everything else that I have with me (as this will be the one on my belt, instead of in a bag/pack). I would still like to have the option to use that skill in some degree if the need presented itself. But as it is right now, the saw cuts, the BK9 splits anything that needs splitting, and the mora feathersticks and does normal camp chores (tent pegs, some food stuff, etc), and I was thinking that a FFG blade might do better as an all arounder to replace the mora.

But you're right, perhaps I need to sort out more what I'm looking for, as its possible that this idea isn't feasible/worth it/thought out well enough. I am still learning about myself, my skills, and what I feel comfortable with. That, and I really found what those are more knowledgeable have helped me learn, so perhaps its not a total waste.

And I didn't say I had an axe (but the other things are spot on).

The main post I was making is that everything is a compromise.....

A reasonable person wouldn't take a knife made for slicing, especially a custom knife that was optimized for slicing and baton with it..... Steel wouldn't matter here......

Now if you wanted an all around blade, general purpose blade that would cut well and can also take some harder use also them then the knife maker would have to be told that BEFORE even talking about steels as you wouldn't even be at that point yet.....

With reasonable geometry 3V would work fine, 1/8" stock, FFG and something in the .015" - .020" range behind the edge and 20 DPS would make a good all around medium knife..... Personally I was thinking A2 at 61 RC......

 

[Ankerson]

Without getting into a whole bunch of math that I'm frankly too lazy and dumb to muddle through, yeah you're on the right track. 3V is both tougher and stronger than 1095 at the same hardness, with the same geometry. Exactly how that breaks down regarding... how much thinner 3V stock can you use to reduce mass without going below the toughness/strength of 1095 at given thickness... I don't know.

The answer to designing a knife is really to decide first on the geometry you want to start with. Geometry is what cuts, and thinner cuts better. THEN worry about alloy selection and HT to suit your needs.

Or.... just use 3V and have it ground any dang way you want -from a big honkin' chopper to a fine little slicer - and have a great deal of confidence in it regardless

People start talking about batoning and the red flags start flying all over the place......

 

[ocnLogan]

Without getting into a whole bunch of math that I'm frankly too lazy and dumb to muddle through, yeah you're on the right track. 3V is both tougher and stronger than 1095 at the same hardness, with the same geometry. Exactly how that breaks down regarding... how much thinner 3V stock can you use to reduce mass without going below the toughness/strength of 1095 at given thickness... I don't know.

The answer to designing a knife is really to decide first on the geometry you want to start with. Geometry is what cuts, and thinner cuts better. THEN worry about alloy selection and HT to suit your needs.

Or.... just use 3V and have it ground any dang way you want -from a big honkin' chopper to a fine little slicer - and have a great deal of confidence in it regardless

Thanks to all of you who responded, as I realize my question was pretty technical, and maybe kind of a pain :/.

Looks like I'll have to do some more thinking, as I've definitely had a shift from very thick knives (BK2) to thinner knives while still being something thicker than a victorinox paring knife. I have tried the Kabar MK1 (great knife), but found myself worrying about the rat tail tang, even though I know it likely won't be a problem, the Becker BK17 (liked it, but found it a bit too thick, because it has a saber grind), the Condor Bushlore (good, but found that I prefer a true scandi grind). And of course my Mora Companion, which I love (but its not great at food prep, nor is it full tang). So I've been looking at options, and found myself wondering if one of these fancy steels might give me some of both worlds.

Thanks again for all who helped .

 

[jstn]

OP, if you are thinking of getting a custom knife made, you should consider James Terrio, who has been replying to this thread. You won't find many (or any) better options.

 

[chiral.grolim]

...while I do some things (like baton what I consider to be reasonably sized and grained wood) that might be "abusive" to my knives, prying isn't one of the things that I do with knives ... I've never once even started to bend even my Mora ...

Batonning IS prying, the grains of wood induce lateral stress on the blade as it forces them apart. A standard Mora (not 'Robust') is 2 or 3/32", pretty thin but not that easy to bend because of the fat scandi (saber) grind that provides that wide area of the blade at full thickness. Take a FFG paring knife with the same spine-thickness and note how easy it is to flex, like a fillet knife. That is where the saber vs full-grind discussion begins - how much cross-sectional area must be at full thickness to provide the desired lateral strength vs flexibility. Moving from hollow to flat to convex bevel is leaving more material (strength) in the blade, i.e. thicker cross-section.

There is nothing wrong with the blade flexing so long as it doesn't permanently deform or fracture. You can find some neat photos of Busse/SwampRat/Scrapyard knives being flexed rather dramatically but returning true. Sometimes you want a blade to flex readily. But a blade that flexes isn't prying anymore, the material is prying it! Axe-blades are designed to be robust for increased toughness, increased mass (for impact force), and also increased strength to pry the wood apart without being "pry'd" upon For thick logs, this is more necessary than for little sticks. A 3/32 Mora can do quite a bit of batonning without much flex. A 3/32" paring knife or machete can also endure quite a bit of batonning but might evince a lot more flex depending on the grind-thickness.

So the toughness factor mainly comes down to how thick the shoulders of the secondary grind can be left and still be reliable (not chip, deform, etc) under its expected use. Spine thickness then helps determine the overall lateral strength of the blade. And so if I'm reading this correctly, this helps not only with things like prying, but with things like not deforming while say... battoning through something? I'm assuming that the strength then is related to the cross sectional area/volume of material in the knife.

:thumbup:

The answer to designing a knife is really to decide first on the geometry you want to start with. Geometry is what cuts, and thinner cuts better. THEN worry about alloy selection and HT to suit your needs.

Or.... just use 3V and have it ground any dang way you want -from a big honkin' chopper to a fine little slicer - and have a great deal of confidence in it regardless

With reasonable geometry 3V would work fine, 1/8" stock, FFG and something in the .015" - .020" range behind the edge and 20 DPS would make a good all around medium knife...

The Survive! Knives GSO-5.1 is a much bigger/thicker knife meant to handle a LOT of abuse, more than a BK-16. CPM-3V, the primary grind is only ~5dps and the edge is ~20dps, 0.020" thick at the shoulder. What can it handle?

[video=youtube;bIx2zaqWim8]http://www.youtube.com/watch?v=bIx2zaqWim8[/video]
[video=youtube;QyBhMK5zlxU]http://www.youtube.com/watch?v=QyBhMK5zlxU[/video]
[video=youtube;ipw7opIQsik]http://www.youtube.com/watch?v=ipw7opIQsik[/video]

OP, if you are thinking of getting a custom knife made, you should consider James Terrio, who has been replying to this thread. You won't find many (or any) better options.

What a reasonable idea Pretty sure he uses CPM-3V as well and offers models similar in size to the BK-16, might even have a more comfortable handle. Hmm... :thumbup::thumbup:

 

[james terrio]

People start talking about batoning and the red flags start flying all over the place......

I know... it's like yelling "Theater!" in a crowded fire, everyone gets all freaked out . I baton stuff all the time and have never broken one of my knives, large or small. On the other hand, I don't warranty against it either, because there are a whole lot of ways to do it wrong. Give someone a big enough hammer or long enough cheater bar, or let them use poor enough technique, and they can break any knife.

I appreciate the kind words, folks I do indeed make many - actually most - of my outdoors-type knives out of CPM-3V.

 

[Ankerson]

I know... it's like yelling "Theater!" in a crowded fire, everyone gets all freaked out . I baton stuff all the time and have never broken one of my knives, large or small. On the other hand, I don't warranty against it either, because there are a whole lot of ways to do it wrong. Give someone a big enough hammer or long enough cheater bar, or let them use poor enough technique, and they can break any knife.

I appreciate the kind words, folks I do indeed make many - actually most - of my outdoors-type knives out of CPM-3V.

That's a lot of my point, there are way too many ways to do it wrong... And it only takes once doing it wrong to really screw up a good knife.....

I wouldn't warranty batoning either... Smart move..... :thumbup: