Toughness or Wear Resistance - What is more important when it comes to edge damage?

[Daniel Fairly Knives]

What is more important when considering potential edge damage in a hard use knife, toughness or wear resistance?

Is a super tough steel like S7 less likely to deform at the edge than one that is still tough but more wear resistant like CPM-3V?

Can you go thinner at the edge with a tougher steel? With a more wear resistant steel?

I'm not looking for a steel comparison, just thoughts on toughness, wear resistance, hardness and edge geometry and how they come into effect when making a knife.

 

[Remyrw]

I think it depends on how you define hard use. Hard use in the context of LOTS of use cutting open packages, cutting rope, skinning multiple animals... or hard use as in chopping tough wood, some digging, prying....

eta: in my folders for edc I prefer more wear resistance, for a utility fixed blade I prefer more toughness, generally speaking. Then geometry comes in with how I'll use it. On most of my folders I prefer a really thin geometry and I'm willing to give up quite a bit of lateral strength to get it. I don't use my folders as pry bars or wedges or anything like that. They're pretty much pure slicing tools. On a fixed blade, the more likely the design is to see chopping duty or get used on things like puncturing metal, digging, prying... the more I go for toughness both in steel and geometry. A smaller more skinning oriented blade will get a less abuse resistant geometry than a chopper, for example. I want the extra toughness in the steel because I am more likely to use the fixed blade for non slicing tasks, but the geometry tends to stay more true to the intended task.

 

[Rick Marchand]

When talking about woods knives, it is my opinion that sacrificing wear resistance for toughness is a logical compromise. From a user perspective, I would rather need to sharpen more often than deal with chipping. Of course, it all depends on how the knife is used so it will always be a very individual decision. The great thing is that as custom makers, we have options.

What kind of HRCs you hittin' with that "rainbow power", bud?!!!

 

[Justin King]

Take away too much of either and you will have a relatively usless knife for anything other than the lightest chores, so obviously a balance is called for. I have always operated under the theory that a bent and dulled knife isn't the most useful tool, but a broken one is even less so. Dull, at least, has a remedy. Fractures do not. Not that that makes either attribute more important, but it may indicate which side one should prefer to err towards in a hard use knife.

 

[james terrio]

Boy, that's a lot of questions! I could happily sit and discuss this stuff all day, but I will try to keep my answers brief and based strictly on my actual experience. Remy's absolutely right, if "hard-use" means you do a ton of slicing but very little chopping, you want hard, thin and extremely wear-resistant. On the other hand, Remy and Rick are both right that if you need to be knocking down saplings and fighting bears toughness becomes a lot more important.

Geometry is King, and determined by task.

High-toughness, well-HTed steels can be ground thinner, even for tasks like chopping. Thin cuts better, always! Something that I habitually preach on is that thin blades/edges are also much easier to sharpen. There is simply less steel to remove to get that final edge bevel back to what you want.

If I had to choose, I would always take toughness over wear-resistance in a survival/combat/general purpose knife. Dulling can be fixed in the field... chipping or an outright break, not so much. However!...

You don't have to choose between high toughness and high wear-resistance if you don't want to; 3V is my go-to for both. There are many other very interesting tool steels available these days that rival 3V in one or more categories, too.

You will notice that not too many forgers work much with 3V, M4, ElMax, CTS-XHP, S35VN and the like; those alloys just aren't suited for it. At the risk of offending my hammer-wielding friends, I respectfully submit that if a maker truly wants to push the performance envelope, he/she should think less about the way they're comfortable working and more about the materials that can help them achieve what they want, and adjust their methods to the material.

 

[Rick Marchand]

James... can you strike a (traditional flint and steel) spark off the spine of a 3V blade? Do you have a small coupon/cut-off you could mail me... maybe 3/4" x 2" in whatever thickness?

 

[Nathan the Machinist]

The highly abrasion resistant high carbide super steels loose a little edge stability. I believe the simpler steels with moderate carbide content resist edge damage the best. Of the knives I have tested, a simple knife in W2 has the best edge retention in a hardwood whittling test that I have attempted to standardize.

 

[Rick Marchand]

The W&SS blade challenge results heavily favored carbon steel. Though, the entries were mostly carbon blades. That mighta had sumpin to do wit it.

 

[Daniel Fairly Knives]

Great stuff everyone! I'm in the shop right now so I will comment more later.

I am talking about woods knives as Rick put it, that is a great description. I mention s lot of questions but I'm really after what will make a knife last when cutting the tougher objects some people encounter in their knife use.

Cutting up nails and rocks is pointless in some ways but what if your edge accidentally hits one? I'm really thinking about knots in wood and that sort of thing though.

 

[Dave Behrens]

The smaller the knife the more wear resistance I want, the larger the more toughness I want. Hard use for me is chopping, batoning, digging prying etc, in that case I always choose toughness.

A dull knife is still a knife, a broken knife is no knife at all.

 

[Jason B.]

Toughness + hardness = edge stability

Edge stability keeps the edge from deforming. It's a universal formula between PM and non PM steels. High hardness and toughness will also allow low inclusive edge angles without changing the deformation rate of the edge apex.

PM steels tend to have higher edge stability due to higher toughness but its often the wear resistance you look for in these steels. Wear resistance can also confuse your thought on when its needed and the "edge retention" it will provide. If you need a knife that's going to see a lot of abrasive cutting and getting dirty the a high wear steel is for you. If you need lasting sharpness then high hardness on low wear resistance steels is the way to go. Hard use type toughness is not really in the intended use of high wear steels.

 

[james terrio]

Mr. T... can you strike a (traditional flint and steel) spark off the spine of a 3V blade? Do you have a small coupon/cut-off you could mail me... maybe 3/4" x 2" in whatever thickness?

Rick, I honestly do not know, I never tried it! I do know I can readily scrape sparks off a ferrocerrocircusmagic-whatever-thingamabob with a 3V blade, but that's entirely different. For a woodsy/survival type knife, being able to strike a good hot spark might be very important to some clients, and there's only one way to find out if it works. That's a great idea, brother!

As it happens I'm in the process of grinding a couple 3V blades; it will be a few weeks before I have them ground, sent in/received back from HT, etc (there is no point asking you to test an annealed sample.) But, hell yes, I will set a piece aside and send you a HT'ed coupon of 3V for testing that! Perhaps such a coupon should be ground square on one edge and have a knife-edge on the opposite edge? I welcome your input.

 

[hardheart]

Hardness and wear resistance for regular cutting and slicing. In that the steel needs to resist deformation from exceeding the elastic range. Harder steels require more force to reach plastic deformation. They can be sharpened to lower angles, and reduced edge angles require less force to cut through media and last longer. Toughness is absorption of impact energy before fracture, so is only for impact cutting, like chopping. S7 is not less likely to deform in all manners, it is less likely to fracture from impact, since it absorbs higher amounts of energy before fracture. The matrix is still not capable of being taken to hardness levels beyond 3V, which has much, much higher wear resistance as well as high toughness.

 

[Matthew Gregory]

You don't have to choose between high toughness and high wear-resistance if you don't want to; 3V is my go-to for both. There are many other very interesting tool steels available these days that rival 3V in one or more categories, too.

You will notice that not too many forgers work much with 3V, M4, ElMax, CTS-XHP, S35VN and the like; those alloys just aren't suited for it. At the risk of offending my hammer-wielding friends, I respectfully submit that if a maker truly wants to push the performance envelope, he/she should think less about the way they're comfortable working and more about the materials that can help them achieve what they want, and adjust their methods to the material.

Truth.

 

[Matthew Gregory]

Mr. Terrio... can you strike a (traditional flint and steel) spark off the spine of a 3V blade? Do you have a small coupon/cut-off you could mail me... maybe 3/4" x 2" in whatever thickness?

I'll just carry a bic lighter. Or how about a nifty little forged bit of striking steel so I don't need to compromise the integrity of the tool designed to chop and pry?

 

[Rick Marchand]

There are reasons why you don't see many supersteel blades in the hands of woods knife users. It might be toughness, ease of sharpening, edge stability, whatever(I know the advantages of alloyed steel). All I'm saying is supersteels don't always fit the bill. EVERYTHING is a compromise. So, you can give me the old "I'll just carry a bic lighter or something else" answer and for most, it makes sense. For me, it no longer holds water because I've been in situations when that is simply not an option and unless you were there, right next to me, you might not understand. If anyone wants to discuss it, I will... but I'll refrain from cluttering up the thread.

 

[Daniel Fairly Knives]

I think it depends on how you define hard use. Hard use in the context of LOTS of use cutting open packages, cutting rope, skinning multiple animals... or hard use as in chopping tough wood, some digging, prying....

eta: in my folders for edc I prefer more wear resistance, for a utility fixed blade I prefer more toughness, generally speaking. Then geometry comes in with how I'll use it. On most of my folders I prefer a really thin geometry and I'm willing to give up quite a bit of lateral strength to get it. I don't use my folders as pry bars or wedges or anything like that. They're pretty much pure slicing tools. On a fixed blade, the more likely the design is to see chopping duty or get used on things like puncturing metal, digging, prying... the more I go for toughness both in steel and geometry. A smaller more skinning oriented blade will get a less abuse resistant geometry than a chopper, for example. I want the extra toughness in the steel because I am more likely to use the fixed blade for non slicing tasks, but the geometry tends to stay more true to the intended task.

I'm talking about chopping and that sort of thing, great points about everything. Thanks!

When talking about woods knives, it is my opinion that sacrificing wear resistance for toughness is a logical compromise. From a user perspective, I would rather need to sharpen more often than deal with chipping. Of course, it all depends on how the knife is used so it will always be a very individual decision. The great thing is that as custom makers, we have options.

What kind of HRCs you hittin' with that "rainbow power", bud?!!!

I agree 100%.

Rainbow Heat Treat hits about 100RC with any steel but I am currently out of distilled mountain lion urine.

I hear you though, RC has a ton to do with everything. Is S7 at 58 better than 3V at 60... many things to ponder. I wish I had a hardness tester in the shop!

I do a lot of testing, that tells me a lot about the heat treat and grind I am going for.

Take away too much of either and you will have a relatively usless knife for anything other than the lightest chores, so obviously a balance is called for. I have always operated under the theory that a bent and dulled knife isn't the most useful tool, but a broken one is even less so. Dull, at least, has a remedy. Fractures do not. Not that that makes either attribute more important, but it may indicate which side one should prefer to err towards in a hard use knife.

Very true! I feel that you have to evaluate the use of the knife first and make it work appropriately for the situation.

Boy, that's a lot of questions! I could happily sit and discuss this stuff all day, but I will try to keep my answers brief and based strictly on my actual experience. Remy's absolutely right, if "hard-use" means you do a ton of slicing but very little chopping, you want hard, thin and extremely wear-resistant. On the other hand, Remy and Rick are both right that if you need to be knocking down saplings and fighting bears toughness becomes a lot more important.

Geometry is King, and determined by task.

High-toughness, well-HTed steels can be ground thinner, even for tasks like chopping. Thin cuts better, always! Something that I habitually preach on is that thin blades/edges are also much easier to sharpen. There is simply less steel to remove to get that final edge bevel back to what you want.

If I had to choose, I would always take toughness over wear-resistance in a survival/combat/general purpose knife. Dulling can be fixed in the field... chipping or an outright break, not so much. However!...

You don't have to choose between high toughness and high wear-resistance if you don't want to; 3V is my go-to for both. There are many other very interesting tool steels available these days that rival 3V in one or more categories, too.

You will notice that not too many forgers work much with 3V, M4, ElMax, CTS-XHP, S35VN and the like; those alloys just aren't suited for it. At the risk of offending my hammer-wielding friends, I respectfully submit that if a maker truly wants to push the performance envelope, he/she should think less about the way they're comfortable working and more about the materials that can help them achieve what they want, and adjust their methods to the material.

Great stuff!

As far as using "super steels" goes that sounds right to me. I will know for sure after I have tested about a million more blades! I am certainly leaning that way in my steel selection.

James... can you strike a (traditional flint and steel) spark off the spine of a 3V blade? Do you have a small coupon/cut-off you could mail me... maybe 3/4" x 2" in whatever thickness?

That is also important to consider especially if that is your customer base, it is very important to consider what people want in a knife. My customers use gasoline!

The coupon idea gets me thinking, I am going to make a bunch of them up and test the edges. That really beats re-finishing a blade!

The highly abrasion resistant high carbide super steels loose a little edge stability. I believe the simpler steels with moderate carbide content resist edge damage the best. Of the knives I have tested, a simple knife in W2 has the best edge retention in a hardwood whittling test that I have attempted to standardize.

Thanks for the input, this is one of the things I have been pondering.

Carbide content and distribution manipulation is a topic I want to look into further. I feel that is how some knives can cut cardboard or rope forever. What makes a toothy edge stay? Does a clustered carbide distribution cause more chips but will it cut "forever"?

I have noticed a major difference between the way O1, 1084, S7 and CPM-3V cut and feel when they are sharp. For example the 1084 just seems nasty sharp and glides through paper while once CPM-3V will slice paper you almost better not touch the blade because it is so sharp to the skin.

The W&SS blade challenge results heavily favored carbon steel. Though, the entries were mostly carbon blades. That mighta had sumpin to do wit it.

I have noticed that as well, this is one of the reasons I wanted to bring his up as a discussion topic.

On paper some steels are way better than others but in practice it is not often that way, I wonder why...

The smaller the knife the more wear resistance I want, the larger the more toughness I want. Hard use for me is chopping, batoning, digging prying etc, in that case I always choose toughness.

A dull knife is still a knife, a broken knife is no knife at all.

Great rules to work by!

Toughness + hardness = edge stability

Edge stability keeps the edge from deforming. It's a universal formula between PM and non PM steels. High hardness and toughness will also allow low inclusive edge angles without changing the deformation rate of the edge apex.

PM steels tend to have higher edge stability due to higher toughness but its often the wear resistance you look for in these steels. Wear resistance can also confuse your thought on when its needed and the "edge retention" it will provide. If you need a knife that's going to see a lot of abrasive cutting and getting dirty the a high wear steel is for you. If you need lasting sharpness then high hardness on low wear resistance steels is the way to go. Hard use type toughness is not really in the intended use of high wear steels.

Great stuff! Thanks for the excellent information.

I hope we discuss this part further! "If you need lasting sharpness then high hardness on low wear resistance steels is the way to go." This is very interesting...

Hardness and wear resistance for regular cutting and slicing. In that the steel needs to resist deformation from exceeding the elastic range. Harder steels require more force to reach plastic deformation. They can be sharpened to lower angles, and reduced edge angles require less force to cut through media and last longer. Toughness is absorption of impact energy before fracture, so is only for impact cutting, like chopping. S7 is not less likely to deform in all manners, it is less likely to fracture from impact, since it absorbs higher amounts of energy before fracture. The matrix is still not capable of being taken to hardness levels beyond 3V, which has much, much higher wear resistance as well as high toughness.

This is another thing I have putting a lot of thought and research into. Thanks very much for the valuable input!

...so toughness and ability to resist edge deformation don't go hand in hand? (or are we more talking about the shock resistance of S7 and other S series steels?)

I'll just carry a bic lighter. Or how about a nifty little forged bit of striking steel so I don't need to compromise the integrity of the tool designed to chop and pry?

That's me, Bic lighter! Lol...

There are reasons why you don't see many supersteel blades in the hands of woods knife users. It might be toughness, ease of sharpening, edge stability, whatever(I know the advantages of alloyed steel). All I'm saying is supersteels don't always fit the bill. EVERYTHING is a compromise. So, you can give me the old "I'll just carry a bic lighter or something else" answer and for most, it makes sense. For me, it no longer holds water because I've been in situations when that is simply not an option and unless you were there, right next to me, you might not understand. If anyone wants to discuss it, I will... but I'll refrain from cluttering up the thread.

I understand and thanks for the comments! Choosing the right steel for the job is really where it is at and there is a whole lot to it.



Thanks everyone for the great discussion so far!

 

[james terrio]

...so toughness and ability to resist edge deformation don't go hand in hand?

Not necessarily, no. As an extreme example, mild steel is very tough but will bend and dent easily... that's not good for a knife blade.

All I'm saying is supersteels don't always fit the bill. EVERYTHING is a compromise.

True on both counts. I have come to prefer "super steels" for my personal knives, but lots of my clients don't... and I'm OK with that! I don't want anyone to get the wrong idea; I've said many times that if the only steel I could get was plain ol' 1084, that would be fine. 1084 is in fact far superior to "super steels" in some ways!

Sorry for the drift, but... I carry a Bic lighter, too, and a ferro-rod when I know I'm heading to the boonies. But Rick's point is valid: what if I lost/forgot them both and only had my knife to make sparks with? Lots of customers are fascinated with being able to do so, even if they never "need" to. I really do think it's worth further testing and will be sending samples to Rick for corroboration.

Carbide content and distribution manipulation is a topic I want to look into further.

Search through some of Nathan's threads, he's written a good deal of very helpful info on exactly that topic. :thumbup:

 

[Matthew Gregory]

I'm buying Marchand a case of Bic lighters and taping them to his underwear.

None of the simple carbon steels offered anywhere near enough wear resistance or overall toughness for the geometries I've found I prefer for general chopping and brush cutting. I tend to make very thing ground knives that might be long but will have low mass, relying on velocity rather than high mass for bite into vegetation. None of the blades I made of 1095 or 1084 survived without serious deformation, loss of edge, or chipping versus the blades I made using the same grind and geometry with steels such as CruForgeV or CPM3V.

Sounds as if technique and application has just as much to do with the end result as the material involved does...

 

[Rick Marchand]

Sounds as if technique and application has just as much to do with the end result as the material involved does...

No argument from me there, G-spot.

I'm buying Marchand a case of Bic lighters and taping them to his underwear.

Ha! Now who looks stupid? I have worn underwear since the last pair rotted off! FACE!!!!