How much does "toughness" matter?

I just texted Mr. T about this, I figure he's the expert on toughness.
 
hugofeynman said:
It’s like the edge vs edge impact. The harder knife wins the battle.
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I would say that being 'tougher' wins the battle. The harder the steel is the more brittle it becomes. But as already mentioned, it's all a tradeoff. A little more of one attribute will take a little away from a different one.
 
Dergyll said:
000Robert 000Robert
Hey sorry friend, I just noticed some of your comments were directed at me. No, I don't own a belt and this knife is fairly new. I used it to cut fish and food for awhile, then touched it up on the white sharpmaker stone. It came to hair shaving REALLY QUICKLY, which now I understand why.

And no, it wasn't petrified wood lol...
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Maybe the manufacturer used a dry belt? Anytime I see a photo of a blade chipping like that that is supposed to be made of quality steel, I always question the person that chipped the blade edge. And using a dry belt to profile/ sharpen a knife is a quick way to ruin the heat treat at the knife bevels.
I'm reading about it online - I have no idea what the knife has been through. And people that throw up photos like that very rarely give a detailed description of the life of the blade as they know it. That's why I always first lay blame on the person using the knife.
 
000Robert said:
Maybe the manufacturer used a dry belt? Anytime I see a photo of a blade chipping like that that is supposed to be made of quality steel, I always question the person that chipped the blade edge. And using a dry belt to profile/ sharpen a knife is a quick way to ruin the heat treat at the knife bevels.
I'm reading about it online - I have no idea what the knife has been through. And people that throw up photos like that very rarely give a detailed description of the life of the blade as they know it. That's why I always first lay blame on the person using the knife.
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Ever wonder why there is a bucket of water next to the grinder in a knifemakers workshop?
 
JoeBusic said:
Ever wonder why there is a bucket of water next to the grinder in a knifemakers workshop?
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That bucket of water means nothing to the edge bevels. The steel is so thin there that you can ruin the heat treat on the bevels without even feeling it. That's why I'm careful who I buy knives from, and why I bought a Wicked Edge to put perfect edge bevels on my knives with without damaging the heat treat.
 
You can turn it around on yourself and ask "would I buy a low toughness steel?"
Ultimately it all comes down to a proper heat treatment, which is where toughness and hardness stems from. At least that's how i understand it
 
000Robert said:
That bucket of water means nothing to the edge bevels. The steel is so thin there that you can ruin the heat treat on the bevels without even feeling it. That's why I'm careful who I buy knives from, and why I bought a Wicked Edge to put perfect edge bevels on my knives with without damaging the heat treat.
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Fingers will burn way before steel gets tempered. Did someone say these things to you or it's your own thought proces?
Edit: Just realized you mean just the tip of the edge. Sharpening does heat up and temper the edge. A part of the edge. It will NOT make the damage that picture showed. A few HRC lower tip will just make it hold an edge a little less. No big deal. All manufacturers sharpen on a belt. Custom makers take a little more care. But in reality it's the users job to sharpen as pleased.
 
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This whole thing makes me laugh. Its like would you rather have a boxer that can take a savage beating and not be fazed, but only have the energy for one round, or a boxer that can punch round after round but one hit and he's knocked out.
 
K.O.D. said:
It's one of those things where there will always be a compromise. Choosing the right tool for the right job is as/more important than the steel. I'm not going to use a Busse to slice apples, nor would I use a puuko the chop logs.

I think with folding knives edge retention is the most important for the tasks most are designed for. Everyone wants that "perfectly balanced" steel, and it has yet to exist.

With camp fixed blades I'll sacrifice some edge retention for strength and toughness. I like a blade that is thin enough that if necessary I can cut food with but stout enough to handle heavier tasks.

Corrosion resistance isn't a big deal to me, I don't sweat much and it's only humid here for 3-4 months. I take care of my knives, dry them off, keep them dry in a case with desiccant or in the sheath.
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Idk m8, things like Magnacut, cruwear, 3/4v come pretty damn close.
 
Dr Rez said:
Idk m8, things like Magnacut, cruwear, 3/4v come pretty damn close.
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I meant about the absolutism. Why can't we have balance, as mentioned. Again, as I've said before, right tool for the right job. I'll take a high hardness thin blade over an obtuse tough blade if I HAVE to choose.
 
K.O.D. said:
I meant about the absolutism. Why can't we have balance, as mentioned. Again, as I've said before, right tool for the right job. I'll take a high hardness thin blade over an obtuse tough blade if I HAVE to choose.
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100%. Right tool right job every time. Geometry>Steel every time as well. Not to mention people often do the same task 2 very different ways, so being objective about a best anything is nearly impossible.
 
A high hardness will hide a bad temper really well until that one day snap or chippy chip and you say hey wait a minute that happened too easily. Then the accusations of abuse.

A bad temper is a bad temper and not in spec with what the steel should be. On the other hand you may never find out.

I suspect if we give out a whole bunch of them to farmers, warehouse worker, and fishermen who will use them it would be interesting to sit back and see what happens.
 
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ferider said:
A Gedankenexperiment: Let's assume Busse had found a steel maker that could make a powdered or droplet version of A8mod and call it Infi.
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There is a misconception among some that making a steel into a powered steel automatically improves that steel. Finer grain or cleaner or something. This is not at all correct. D2 is a great example of this in the "real world" of knife steels.



I think that most of us understand by now that forging a clean modern steel does not automatically improve it. It usually only introduces opportunities for flaws.

Pattern welded "Damascus" steel does not usually improve a steel. It mostly just introduces opportunities for flaws.

There have been times and materials that were improved by these primitive mechanical processes, but I think that most of us understand that the best modern materials aren't usually improved by whacking it with a hammer. The same is true of PM materials. Spraying a metal into a powder and then compressing it into a fully dense homogenous material does not inherently improve the material, it usually only introduces the opportunity for flaws.

As a rule, we use the PM process not to improve metal, but to allow the creation of alloys not readily possible with a conventional melt. As a rule, it's not to improve the metal, it makes alloys possible. For example, you might want a lot of vanadium carbide in your steel, but it falls out of solution too fast when used in large amounts, so the only way to get a good distribution is to use a PM process.

I do not think A8 will be improved with the PM process. I think it doesn't need it and you'll probably only introduce problems.

A few things I'd like to touch on:
Abrasive wear resistance is not the same thing as edge retention.
Toughness is not the same thing as durability.

If you want a knife that holds an edge well and holds up to rough use, an impact test (a measurement of energy absorbed in a break) and wear resistance (often a measurement of material lost in light controlled cuts in a soft abrasive material) is not a perfect measurement.

It is easy to make a knife that doesn't break. It is not easy to make a knife that is durable, stays sharp and cuts well and doesn't break.

There is a misconception that there is a spectrum from soft and durable vs hard and brittle and you have to choose a point in this 2-dimensional space. The reality is, there is a depth dimension to this with more advanced alloys and heat treats and it is possible to have abrasive wear resistant materials that are also hard with fine edge stability that are also very durable and hard to break.
 
000Robert said:
Maybe the manufacturer used a dry belt? Anytime I see a photo of a blade chipping like that that is supposed to be made of quality steel, I always question the person that chipped the blade edge. And using a dry belt to profile/ sharpen a knife is a quick way to ruin the heat treat at the knife bevels.
I'm reading about it online - I have no idea what the knife has been through. And people that throw up photos like that very rarely give a detailed description of the life of the blade as they know it. That's why I always first lay blame on the person using the knife.
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Here you go, skip to 1:20 to see the sharpening. Take it for what it is, the video is 10 years old so not sure if the processes have changed? I make no judgements or statements on it, as I'm not a knife maker. Except for the lack of masks, holy moly, I started coughing just from watching that dude sanding the handle!

 
Nathan the Machinist said:
As a rule, we use the PM process not to improve metal, but to allow the creation of alloys not readily possible with a conventional melt. As a rule, it's not to improve the metal, it makes alloys possible. For example, you might want a lot of vanadium carbide in your steel, but it falls out of solution too fast when used in large amounts, so the only way to get a good distribution is to use a PM process.

I do not think A8 will be improved with the PM process. I think it doesn't need it and you'll probably only introduce problems.
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Thanks a lot, Nathan. I learned something. That finally explains to me why some steels come only in powder form, and others (like AEB-L) only as ingots. I guess I have to study Larrin’s crystal/micro-graphs some more ...

I will ask you some follow up question on D2 vs. CPM D2 vs. PSF27 in your subforum in the future, if you don’t mind.

Roland.
 
ferider said:
Thanks a lot, Nathan. I learned something. That finally explains to me why some steels come only in powder form, and others (like AEB-L) only as ingots. I guess I have to study Larrin’s crystal/micro-graphs some more ...

I will ask you some follow up question on D2 vs. CPM D2 vs. PSF27 in your subforum in the future, if you don’t mind.

Roland.
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I learned that about AEB-L, forget who here told me that. I asked about powder metallurgy AEB-L, and someone pointed out that it would be no improvement because it's a simple alloy that doesn't require powder metallurgy to form.
 
Rooster81 said:
Here you go, skip to 1:20 to see the sharpening. Take it for what it is, the video is 10 years old so not sure if the processes have changed? I make no judgements or statements on it, as I'm not a knife maker. Except for the lack of masks, holy moly, I started coughing just from watching that dude sanding the handle!

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Not sharpening. It's convexing the edge. I guess sharpening was done just before hand polishing.
 
Nathan the Machinist said:
As a rule, we use the PM process not to improve metal, but to allow the creation of alloys not readily possible with a conventional melt. As a rule, it's not to improve the metal, it makes alloys possible.
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I thought the PM prices *could* "improve" steel by reducing the size of carbides and making the steel matrix more homogenous? Not all steels, but definitely some of them, kind Cruwear?

^ not trying to argue, generally want to learn.
 
Rooster81 said:
I thought the PM prices *could* "improve" steel by reducing the size of carbides and making the steel matrix more homogenous? Not all steels, but definitely some of them, kind Cruwear?

^ not trying to argue, generally want to learn.
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I'm also a bit confused with this one. I'm no expert, but I thought it was widely agreed by the experts that for example CPM-D2 is considerably tougher than ingot D2 because the carbides are smaller and more spread out and therefore has less potential stress points in the matrix of the steel.
 
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