How much does "toughness" matter?

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Rooster81

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Or maybe a better question is at what point is additional toughness a moot point, at least in a small to medium sized knife?

I watched a video of a hard use test of a 4 inch bushcraft knife. The steel is elmax at 60-61 hrc. The knife has minimal damage after being batonned through a metal pan. By all accounts, the steel isn't all that tough, right? So it's there a sort of minimum toughness where going any higher is overkill?
 
Rooster81 said:
Or maybe a better question is at what point is additional toughness a moot point, at least in a small to medium sized knife?

I watched a video of a hard use test of a 4 inch bushcraft knife. The steel is elmax at 60-61 hrc. The knife has minimal damage after being batonned through a metal pan. By all accounts, the steel isn't all that tough, right? So it's there a sort of minimum toughness where going any higher is overkill?
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Toughness is important because, with a high toughness steel, you can have a very thin edge without risks of chipping. And a thin edge is key to performance.
So you should not compare only the toughness but also the thin edge that you can use due to this toughness.
 
Toughness per se is a misleading term. There are more things at stake. Usually toughness means resistance to break. What can be seen as tough in a knife is also compression strength. Compression strength is enhanced with carbides. There comes the issue. Elmax will break after just a little bend so it can't be called tough. Toughness is key for edge holding. It means the edge can be held true with lateral forces.
So, batoning in reality is not a test of toughness only but of compression strength primary and toughness as secondary.
A lot is going on in a knife. :)
 
Good question I've been wondering this myself with Magnacut rolling out. I feel like P patrickguignot had a good point about edge thinness.

I watched a guy at bladeshow flex a blade in sv45vn I was shocked it didn't snap. I mean he really flexed it. It sprung right back to where it started. It made me wonder how tough steel is even when toughness is considered low.
 
Grind, thickness and a good HT can make a huge difference. Although all my hard use knives are in btw my favourite steels which are all or have proven to be very tough for me - 80crv2, 5160, 1055-1070, 3v, sleipner, Aeb-L, 14c28n, 12c27 etc...

Although if used appropriately most steels will be tough enough on a decent knife, abuse or misuse playing a bigger part imo with regards to damage.
 
I don't find above the norm toughness at all helpful for what I do with pocket knives. Hardness, carbides, and edge angle only matter there for me (and added toughness does not let me go to lower angles with less damage overall)

I do find it helpful for carving wood and other tasks with wood. I assume the harder material and type of cuts benefit from the added toughness.
 
Im assuming your referring to the DBK video. Just proved that TRC's Elmax is tougher than chinese aluminum.. 😆

If there were 0 trade-off's, I will take as much toughness as I can get. But in reality there are always trade-off's so it really just depends on what traits you value more..
 
Corton93 said:
Im assuming your referring to the DBK video. Just proved that TRC's Elmax is tougher than chinese aluminum.. 😆
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Lol, yup. I was really surprised they went with elmax. Not because I think elmax isn't good or anything, just thought they were fans of 3v, Cruwear, and Magnacut.
 
It's funny that most of the knife community is all about edge retention, edge retention, edge retention. Most, outside of the knowledgeable people in this thread and others sprinkled throughout, don't even really understand what toughness is. I used to think that it was how much bend a blade could take before fracturing too. Thank god we have people like Larrin in our community, I feel like us knife people have come a long way in our steel knowledge in the passed few years.
 
My third grade teacher Miss Heller was tough. She had a thumb and forefinger like a vise grip, especially when applied to the ear of a misbehaving kid. She would probably be 3V in terms of steel, and character. That said, I don't hammer my knives through knotty wood or chop through concrete blocks, so pretty well any well heat-treated blade with good geometry is tough enough for my purposes.
 
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Rooster81 said:
Or maybe a better question is at what point is additional toughness a moot point, at least in a small to medium sized knife?

I watched a video of a hard use test of a 4 inch bushcraft knife. The steel is elmax at 60-61 hrc. The knife has minimal damage after being batonned through a metal pan. By all accounts, the steel isn't all that tough, right? So it's there a sort of minimum toughness where going any higher is overkill?
Click to expand...
Say it with me, "Geometry"
 
To simplify things (and hopefully not oversimplify):

1. When talking about cutting stuff (let's put aside choppers and other speciality knives for a minute), THIN edge geometry is the single most important factor. A thin edge (low edge angle and thin behind the edge) will cut better and longer than a thick one.
2. In order for that thin edge to remain stable, it must be HARD. Trible B Handmade (who's in this thread) has posted several interesting stories on Instagram recently showing that often times a dull, damaged edge is mistakenly thought to have chipped, when in reality it rolled and deformed because the steel was just too damn soft.
2. Also in order for that thin edge to remain stable, it should be TOUGH to prevent chipping. An incredibly thin ceramic knife edge is going to be super hard, but its lack of toughness will result in a ton of chipping right and the edge will become useless fairly quickly.

There's of course a tradeoff here: the higher you bring the hardness of a steel, the lower its toughness will be. And perhaps hardness might be more important than toughness—there are debates about that. And then there's wear resistance, which has mostly to do with carbides. So it gets complicated. But at the end of the day, in my practical experience I tend to prefer steels that have a good balance of hardness and toughness, like CPM CruWear.
 
So I guess, after over analysing everything, here are my rough conclusions so far.

Pocket knives:
- Steel and geometry don't matter a whole lot (in the sense that you can go pretty thin without worry), assuming it's from a reputable knife maker and assuming the knife will be used for mostly cutting/slicing tasks.
- Might as well go with stainless steel so you don't have to worry about rust.
- Might as well go with the steel with the best edge retention that you feel confident you can sharpen.

Fixed blades:
- Assuming it will be used for "harder" use tasks (at least compared to a pocket knife), the steel isn't as important as the thickness and geometry of the knife.
- Because a thicker stock steel with more robust geometry is more important than type of steel, might as well go stainless or semi-stainless.
-Most steels are "tough enough", even those considered lower toughness steels like Elmax and K390.
- Also assuming the knife is from a reputable manufacturer.
 
brancron said:
To simplify things (and hopefully not oversimplify):

1. When talking about cutting stuff (let's put aside choppers and other speciality knives for a minute), THIN edge geometry is the single most important factor. A thin edge (low edge angle and thin behind the edge) will cut better and longer than a thick one.
2. In order for that thin edge to remain stable, it must be HARD. Trible B Handmade (who's in this thread) has posted several interesting stories on Instagram recently showing that often times a dull, damaged edge is mistakenly thought to have chipped, when in reality it rolled and deformed because the steel was just too damn soft.
2. Also in order for that thin edge to remain stable, it should be TOUGH to prevent chipping. An incredibly thin ceramic knife edge is going to be super hard, but its lack of toughness will result in a ton of chipping right and the edge will become useless fairly quickly.

There's of course a tradeoff here: the higher you bring the hardness of a steel, the lower its toughness will be. And perhaps hardness might be more important than toughness—there are debates about that. And then there's wear resistance, which has mostly to do with carbides. So it gets complicated. But at the end of the day, in my practical experience I tend to prefer steels that have a good balance of hardness and toughness, like CPM CruWear.
Click to expand...
I'm beginning to think that edge stability relies more on hardness than on toughness. Hardness is analogous to strength- if the steel is very hard/strong then it resists stresses applied at the edge. When the strength is exceeded then the edge breaks (chips). If a steel is very tough but not as hard/strong then when the strength is exceeded at a lower level then the edge will roll rather than chipping.

The same thing would apply to the overall blade- if you are batoning or prying then when the stress limit of the blade is reached the blade will bend, or for a harder steel the stress limit would be reached at a higher level and the blade would break. The advantage here of a tougher steel is that when you see your blade with a bend in it you know to stop what you are doing and you end up with a bent blade instead of 2 pieces of blade.

The one exception to all of this really does depend on geometry. Some steels are sensitive to stress concentrations at holes and notches and when you stress the blade it will fracture at one of those discontinuities. A tougher steel will resist this better so unless the blade is carefully made with these factors in mind a tougher steel will create a blade that will resist abuse better. There are enough variables involved that it can be difficult to compare 2 blades on paper. There used to be the "hockey mask" guys on youtube that would abuse blades without mercy and it was interesting to see which blades could take it and which could not.
 
LimpCroissant said:
It's funny that most of the knife community is all about edge retention, edge retention, edge retention. Most, outside of the knowledgeable people in this thread and others sprinkled throughout, don't even really understand what toughness is. I used to think that it was how much bend a blade could take before fracturing too. Thank god we have people like Larrin in our community, I feel like us knife people have come a long way in our steel knowledge in the passed few years.
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Strength is the ability to take a load without permanently deforming.

Toughness is the ability to take an impact without damage, i.e., chipping, cracking, etc.
 
Toughness is the most important quality in a knife to me as far as self-defense and survival are concerned, especially in my fixed blades. If I'm trying to stab a scumbag and I miss and stab concrete, I want the concrete to scream in agony, not my knife.
 
patrickguignot said:
Toughness is important because, with a high toughness steel, you can have a very thin edge without risks of chipping. And a thin edge is key to performance.
So you should not compare only the toughness but also the thin edge that you can use due to this toughness.
Click to expand...
Never thought of it that way. I always thought toughness was essential in big blades for withstanding punishment, and not as important for small blades since we don’t really subject our folders and Kepharts to much abuse, i.e. hacking and batoning.

What about hardness though? Does high hardness allow for a thin edge with little risk of chipping as well?
 
How much does toughness matter.

Not much until that day when your 65 Rockwell super cutter that unknown to you has not had a proper tempering cycle snaps with minimal lateral force when it should not have and a whole bunch of fanatics accuse you of abusing your knife.
 
DangerZone98 said:
Never thought of it that way. I always thought toughness was essential in big blades for withstanding punishment, and not as important for small blades since we don’t really subject our folders and Kepharts to much abuse, i.e. hacking and batoning.

What about hardness though? Does high hardness allow for a thin edge with little risk of chipping as well?
Click to expand...

Hardness is also important of course. It's the balance toughness/hardness that is critical in order to have a thin geometry.
But many people think toughness is only for big choppers and that's a mistake.
It's very well described by Brancron in this thread.
 
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