How much does "toughness" matter?

ferider said:
Yeah, but are you sure it's Elmax ? :)
Click to expand...
Hey, I never made that claim...they did ;)

Strike two BRK, before you lose your 34th biggest fan, and I make a big stink in Feedback about being your biggest 100 percentile fan and standing feeling totally betrayed on top of Mount Greylock, resorting to using a SAK and Delica to carve a walking stick.
 
Rooster81 said:
I'm not sure I'd call the study "piecemeal". Dr Larrin developed Magnacut and works with major knife manufacturers.
Click to expand...
Yes, he did, and MagnaCut is amazing stuff. Comparing D3V to 3V broadly is difficult, because Nathan and Peters heat treat 3V very specifically to Carothers designs by their proprietary 'Delta' heat treat protocol. To test it fairly, you'd have to do industry-standard 3V heat treat on Carothers designs and then compare them. I don't think anyone has done that, but plenty of anecdotal evidence suggests that D3V as implemented in Carothers designs is a stellar combination.

As Larrin points out, a substantial amount of a knife's qualities is determined by the grind, thickness, thickness behind the edge, etc., or the physical dimensions of the knife blade rather than the steel or the heat treat thereof. So comparing knives of different steels or heat treats without holding those other characteristics as constant doesn't produce super helpful information.
 
Dergyll said:
Hey, I never made that claim...they did ;)

Strike two BRK, before you lose your 34th biggest fan, and I make a big stink in Feedback about being your biggest 100 percentile fan and standing feeling totally betrayed on top of Mount Greylock, resorting to using a SAK and Delica to carve a walking stick.
Click to expand...

We all have a BRK knife somewhere ... :)
 
madcap_magician said:
So comparing knives of different steels or heat treats without holding those other characteristics as constant doesn't produce super helpful information.
Click to expand...

Agreed, which is why I like to look at BOTH lab test data AND real world use. I think data accumulated from consistent, controlled tests is a great reference and starting point.

But there are so many other variables in play that you also have to look at user experience. In other words, empirical and theoretical are both important. It's also why I appreciate knife makers like Spyderco, they give us so many knives and steels to play with! And Dr. Larrin for his tests!
 
Many terms from the Young's modulus has been used here. I'm no physic expert, but let put it in scenario to see them more clear. The force applied to the edge (vertical force) and the force applied to the blade (lateral force) are two different thing, therefore 2 different kinds of toughness.

Yield strength: maximum amount of stress that material can withstand while staying in the elastic (reversible) deformation regime.
- This is where the "flex test" has it value. This is what you and the Youtuber looking for when you guys do need to pry and do other abusive action.
- Flex test shouldn't be just angle bent, it needs to have a force reader on it as well.
- It is why the spring steel is used for blade.

Ultimate strength: The strength of plastic deformation (where the thing can turn back to its original form by itself).
- Edge rolled easy is the sight of low yield strength, rather than anything else. And if it is rolled or permanently flexed, what is the toughness even for?
- High ultimate strength is usually mistaken for high toughness, but it is also not the case. Tou can't pry :poop: with with something flexed.

Toughness: amount of energy that a material can absorb before fracture.
- So basically how much it takes before it break when it breaks. Total of both kind of strengths the thing has.

Geometry: Things like I-beam is stronger, both strength and toughness, for the same mass and other quality compare to a square beam.
- The blade fuller is the way of shaving the weight with minimal reduction on the blade strength.

Edit: Young's modulus however, has nothing to do with edge retention. Also, what do you consider a blade to be broken? When there is plastic deformation or when it is shattered and broken into piece? /end edit

Thicker blade stock will always add more strength and toughness, but then you get heavier thing. This is the case for many 1095 knives, they are just heavy blade. And with the tang, the full width tang is loved for more strength. Yet, rat tang with the right geometry of the angle between the blade and the tang, it create a strong yet lighter blade (like the sharp angle on Kabar is way weaker than a rounded angle on other rat tang).

Physic doesn't care about your opinion. Overbuild is easy, but not the most performance.

The Nerd's test is the way that a scientific test should go by, by keep the environment, size and criteria as close as possible, with only few things different to test the different behaviors. Though, Larrin's toughness test results used the lateral force strike to determinate the strength of the steel, which might have a different behavior of toughness compare to vertical strike on the edge. He does have vertical strike test on the blade, but it was not included to his final table.
 
Last edited:
JoeBusic said:
This looks like it's written by a FB hate bot.
Click to expand...

I kinda expected you to say something like that. I love Knife Steel Nerds. I also have Larrin's new book. I read the article when it came out or there abouts. Look for yourself under toughness - it says from a 'piecemeal' study.

People like you just through up a link to an article like that thinking that nobody will actually read it and just believe you outright.

I own some Carothers knives with D3V steel. I've cut polymer and wood with them with no problems, and even better than that, I have to look at the edges under magnification to see if the edge even looks like it cut anything!

I've slammed the edge of my Carothers D3V steel knife into the steel handle of a welding machine, and the edge still looked like I had just sharpened it. I slammed it into the handle on accident, but that doesn't change the fact that it happened.

I've seen what D3V can do with my own eyes on really tough stuff.
 
Rooster81 said:
I'm not sure I'd call the study "piecemeal". Dr Larrin developed Magnacut and works with major knife manufacturers.
Click to expand...

So, you didn't read the article either??

Here's the first paragraph under "Toughness".

"Toughness

With toughness it is a bit harder to link to only one article as I don’t really have a summary of all of the toughness testing that we have done. Mostly it has been presented piecemeal with all of the studies that we have done on optimizing heat treatments of different steels like CPM-CruWear, AEB-L, 52100, etc."

Anything else that I can help yall with?
 
000Robert said:
I kinda expected you to say something like that. I love Knife Steel Nerds. I also have Larrin's new book. I read the article when it came out or there abouts. Look for yourself under toughness - it says from a 'piecemeal' study.

People like you just through up a link to an article like that thinking that nobody will actually read it and just believe you outright.

I own some Carothers knives with D3V steel. I've cut polymer and wood with them with no problems, and even better than that, I have to look at the edges under magnification to see if the edge even looks like it cut anything!

I've slammed the edge of my Carothers D3V steel knife into the steel handle of a welding machine, and the edge still looked like I had just sharpened it. I slammed it into the handle on accident, but that doesn't change the fact that it happened.

I've seen what D3V can do with my own eyes on really tough stuff.
Click to expand...
Still boting...
 
JoeBusic said:
Nerd as in Knifesteelnerds.com. I explained the importance of understanding the difference between compression strength and toughness. Cutting nails and such is a matter of compression strength more than toughness. My Titanium blades are cutting nails.
Click to expand...

No, it's impact toughness - impact from the hammer hitting the knife, and impact of the edge driving through the nail, chain link, or whatever.
 
000Robert said:
No, it's impact toughness - impact from the hammer hitting the knife, and impact of the edge driving through the nail, chain link, or whatever.
Click to expand...
Man, you're shooting yourself in the feet now. Impact toughness measurement like Charpy and Izod are measuring force that SEPARATES material, not compress. When a hammer impacts the sample, impact site is under compression, which makes the opposite side under tension. So it is a shock separation. Carbides and cracks (like in plate martensite) are crack propagation sites and will weaken the steel.
When hammering a knife thru a nail or anything else, the blade is under compression, not tension. Ergo, two completely different things. Toughness in hammering nails is secondary.
 
jstn said:
Edge durability is the real desirable property for me. If a knife is tough because it is soft, the edge will roll. If it is too hard the edge will chip. The balance of the two leads to a durable edge that will resist chipping and rolling.
Click to expand...

You are confusing strength, with toughness. Strength is the ability to take a load without permanently deforming.
 
000Robert said:
So, you didn't read the article either??

Here's the first paragraph under "Toughness".

"Toughness

With toughness it is a bit harder to link to only one article as I don’t really have a summary of all of the toughness testing that we have done. Mostly it has been presented piecemeal with all of the studies that we have done on optimizing heat treatments of different steels like CPM-CruWear, AEB-L, 52100, etc."

Anything else that I can help yall with?
Click to expand...
Hey, no problem friend! I thought you might be using "piecemeal" in a derogatory manner (hard to tell context on the forums sometimes).
 
JoeBusic said:
Man, you're shooting yourself in the feet now. Impact toughness measurement like Charpy and Izod are measuring force that SEPARATES material, not compress. When a hammer impacts the sample, impact site is under compression, which makes the opposite side under tension. So it is a shock separation. Carbides and cracks (like in plate martensite) are crack propagation sites and will weaken the steel.
When hammering a knife thru a nail or anything else, the blade is under compression, not tension. Ergo, two completely different things. Toughness in hammering nails is secondary.
Click to expand...

It's still an impact. It sounds to me that you are mixing strength and toughness together. I'm not an expert so I guess we'll just agree to disagree.
 
Rooster81 said:
Hey, no problem friend! I thought you might be using "piecemeal" in a derogatory manner (hard to tell context on the forums sometimes).
Click to expand...

Yeah, it is hard to tell sometimes. And I'll admit to being lousy at always writing what I mean correctly. There are probably 20 year olds that have more online experience than I do.
 
jstn said:
Edge durability is the real desirable property for me. If a knife is tough because it is soft, the edge will roll. If it is too hard the edge will chip. The balance of the two leads to a durable edge that will resist chipping and rolling.
Click to expand...
There have certainly been folks testing edge stability on some of the harder and less tough knives (maxemet for example) that have reported positive results. Wasn't it deadboxhero who was carving up brass or aluminum rods with various steels?
 
You must log in or register to reply here.
Back
Top