Hard versus Tough and why they don't mix.

james terrio said:
High hardness and high toughness are not mutually exclusive - unless you limit your steel choices.
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Thanks for that dose of reality James. Name a few of them for us please.

Hope you had a nice holiday, Fred
 
Fred.Rowe said:
Hope you had a nice holiday...
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I did, thank you kindly! My very best wishes for a Happy New Year for you and yours, Fred :)

CPM-3V and Elmax are both very tough at relatively high hardnesses (58-62 Rc)... equal to or better than classic high toughness steels like O1 and 1095 in the same range... with far better edge-holding properties. Corrosion-resistance is barely a factor at all to me, but it's very important to some clients, and 3V and Elmax have that in spades over any plain carbon steel. They are my personal choices for the knives I make for, and carry/use myself.

Even CPM-154 is a great deal tougher (both in terms of resisting chipping at the edge, and just not breaking when you thump on it/chop with it) than most people give it credit for. I was frankly stunned at how well thin edges of CPM-154 hold up under severe abuse when I first began testing it. We don't usually talk about CPM-154 as being a "high-toughness" steel, but I sell a fair amount of 5" blade survival/combat type knives in CPM-154 at 58Rc, to people who beat on them just for fun, and have never had a complaint about chipping or breakage.

In fact, the only chipping complaint I've ever gotten was from a fellow who dropped his thin-edged THK custom necker in Elmax from waist-high in such a way that it landed perfectly on the edge, against a chunk of quartz on the ground (I'm still trying to figure out how he managed that, but that's what he said :rolleyes:). He sent the knife back to me for repair, and the "chip" measured no more than 1/16" in any dimension and was easily sharpened out. I don't consider that a failure of the steel or HT.

The vast majority of winning competition cutters the last several years are using CPM-M4, ground very thin at the edge and tempered very hard. Those cats put more stress on their knives in a single minute than most of us do all week... and it holds up just fine, while exhibiting outstanding wear-resistance and edge stability.

None of those alloys requires differential hardening to maintain their toughness. They are all more difficult to sharpen than leaner alloys, without question; I find that thin geometry and the pleasure of needing to sharpen much less often, outweigh that.

Makers who forge their blades generally limit themselves to much simpler alloys, simply because high-alloy "powder" steels like those I've mentioned are much more difficult to shape with heat and impact. Stock-removal guys have no limitations in that regard. We get to use whatever-the-heck we feel like using... grinding belts don't really know the difference. :D

I'm not "against" simple steels, by any means... I still make knives out of O1 and 52100, and would happily, and confidently rely on them for rough use or if I was lost in the woods. They definitely work, and they're not going away any time soon :)
 
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james terrio said:
The vast majority of winning competition cutters the last several years are using CPM-M4, ground very thin at the edge and tempered very hard. Those cats put more stress on their knives in a single minute than most of us do all week... and it holds up just fine, while exhibiting outstanding wear-resistance and edge stability.
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Why do they use it? I've always wondered about that. I would have expected 5160 or maybe 3V. I'm guessing it's because they want a thin edge, so edge stability and hardness are important, and M4 shines there?

james terrio said:
None of those alloys requires differential hardening to maintain their toughness. They are all more difficult to sharpen than leaner alloys, without question; I find that thin geometry and the pleasure of needing to sharpen much less often, outweigh that.
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For the same geometry, I would agree they take longer to sharpen. When the exotic steels are run thin and hard, I think they sharpen faster and easier though. Much less material to remove, and much less burr formation. I would also argue that diamond sharpeners can significantly narrow the time it takes to sharpen as well.

james terrio said:
I'm not "against" simple steels, by any means... I still make knives out of O1 and 52100, and would happily, and confidently rely on them for rough use or if I was lost in the woods. They definitely work, and they're not going away any time soon :)
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Yup! It's nice with all the choices today we don't have to choose, we can use and enjoy both.
 
sodak said:
Why do they use it? I've always wondered about that. I would have expected 5160 or maybe 3V. I'm guessing it's because they want a thin edge, so edge stability and hardness are important, and M4 shines there?
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Exactly. :thumbup: 5160, 1084, 3V etc are all plenty tough enough, but they don't have the same wear resistance that CPM-M4 does.

sodak said:
For the same geometry, I would agree they take longer to sharpen. When the exotic steels are run thin and hard, I think they sharpen faster and easier though. Much less material to remove, and much less burr formation. I would also argue that diamond sharpeners can significantly narrow the time it takes to sharpen as well.
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I agree :)
 
james terrio said:
The vast majority of winning competition cutters the last several years are using CPM-M4, ground very thin at the edge and tempered very hard. Those cats put more stress on their knives in a single minute than most of us do all week... and it holds up just fine, while exhibiting outstanding wear-resistance and edge stability.
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Ed Schempp had some fairly interesting things to say on the Spyderco forum about the use of M4 in cutting competitions. Long term durability is proving to be an issue.
 
Bugout Bill said:
Ed Schempp had some fairly interesting things to say on the Spyderco forum about the use of M4 in cutting competitions. Long term durability is proving to be an issue.
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I'd be interested to read that. Got a link?
 
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