Toughness vs. Toughness

[jmforge]

Confusing? Sure, but bear with me. Generally, when us knife making folks discuss toughness, we are talking about Charpy impact toughness. On the other hand, I suspect that when someone is looking at say one of those "hard to the core" high speed low drag differentially hardened 1095 tactical knives, they may be thinking about tensile strength or something similar. That is to say, I can pry rocks ( as opposed to chopping them) and use my knife as a ladder rung stuck into a tree without it breaking. So what is the difference and how would those properties interact. I have heard stories about stuff like L6 having crazy tensile strength, but maybe not as much impact toughness as say 8670 or 5160. i have also heard about 9260 being as "tough" as the similar 5160, but having more "ductility" because of the increased silicon. Anyone care to unconfuse me and talk about how these different properties impact our little hobby?

 

[tkroenlein]

Well I sure can't unconfuse you, or myself for that matter.

But there is a world full of knives that are made out of "not tough" steels like 1095 and O1 and are well reputed for being "tough."

That got myself to thinking when the average user talks about tough, they're really not talking about toughness, but about how good that edge holds up cutting stuff they know they shouldn't, how the tip don't break when you pry a fence steeple out and how much weight you can put on it.

And like you say, strength is really what you want for all of that.

I guess I kinda feel like the level of toughness needed for *most* knives is well below what most common steels possess.