What is the Difference Between edge retention and toughness?

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panzerjunky

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As I am looking at steels for knife making, I have been using 1095 and 80crv2 I see that 1095 has better edge retention but 80crv2 is supposedly tougher.
What does that mean ???? aren't they kinda one in the same ?? and while we are on the topic, and I am sure this will open a can of worms but ......what is a user friendly steel (I do stock removal) with good edge retention but a bit of corrosion resistance?
 
All the terms that describe the cutting edge of a knife blade are directly related to the heat treatment of that specific knife and the steel it is made of and the specific allows in that steel. The knife maker can alter the retention, toughness, ductility of a knife blade by changing the heat treatment giving different hardness which effects the edge performance. Blade geometry is another factor in edge retention and durability. Change the shape and you change all these factors. When I discuss blade performance it's usually in terms of geometry and heat treatment and I let the terms that describe the performance to the individual.
Happy grinding, Fred
 
I tend to think there are four ways for a blade to get dull:
1: corrosion - addressed by corrosion-resistant steel (high polish and coatings help the flats, but won't help preserve the edge)
2: abrasion - addressed by wear-resistant steels
3: chipping - addressed by tough steels and/or by wider edge geometry
4: rolling - addressed by high-hardness steels and/or by wider edge geometry

But I'm just some random guy. I'd like to hear Larrin Larrin weigh in on this. And Nathan the Machinist Nathan the Machinist was quoting Roman Landes about edge retention recently, and I'd like to hear more about that (I can't read Landes because I don't read German).

I'm specifically calling on those two because Larrin is the metallurgist who writes Knife Steel Nerds and developed CPM Magnacut and AlexUltra steels; Nathan is the knifemaker from Carothers Performance Knives, whose knives seem to win all the BladeSports events. So they both clearly know some things about how knives get dull (or not).
 
Toughness is related to flexibility, but wear resistance is related to hardness. Think about glass, it's hard to scratch but if you try to bend it the glass shatters. Hard but not tough.

As for steel, the big question is how are you heat treating? I like W2, 5160 and similar; but if you want corrosion resistance you need to go stainless. Honestly everyone seems to have a set of steels they like for what they are doing, so work out what you're doing and you'll find the steels that you want to work with.
 
Edge retention is the ability to retain a sharp edge. As the guys above said, it is a combination of hardness, rust resistance, abrasion resistance, rolling, chipping, heat treatment,...

Toughness is the ability to not break in half. If steel A is tougher than steel B, then steel A is harder to break than steel B.

However, this is a gross oversimplification, I don't think we could go in depth into the engineering and chemistry in just a forum post.
 
Larrin's book, Knife Engineering, covers it pretty well. It also has excellent HT recipes for most steels that are designed to get teh best combination of features.
 
With regard to steel...

Toughness, is the ability to deform, without catastrophic failure.
Strength, is the ability to resist deformation.

You can't max out on both... it is a balancing act.

These two attributes will dictate how steel behaves after it reaches its elastic limit.... will it deform(bend, roll) or will it resist until failure(break, chip). Abrasion Resistance and Edge Retention is also determined by these attributes but I don't know enough to go into any more detail than that.
 
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Gol Dang
I so 100% appreciate the time yall spend answering my questions. I have that fella's knife engineering book .... thought it was a tad over my head. I will now revisit.
thanks again
Jerry
 
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