Spyderco Forums

Deadboxhero wrote: ↑

Mon Nov 20, 2023 9:46 am

The effect was still present after cutting the same amount of rope, It wasn't just a fluke with the initial sharpness that we saw the behavior.

Ah, that makes more sense, thanks.

I bet the slicing impact is more dramatic. I wonder how to quantify/measure it though. Maybe depth of slice with a thick fibrous material.

zhyla wrote: ↑

Mon Nov 20, 2023 10:47 am

Deadboxhero wrote: ↑

Mon Nov 20, 2023 9:46 am

The effect was still present after cutting the same amount of rope, It wasn't just a fluke with the initial sharpness that we saw the behavior.

Ah, that makes more sense, thanks.

I bet the slicing impact is more dramatic. I wonder how to quantify/measure it though. Maybe depth of slice with a thick fibrous material.

Yeah, the tomatoes were sliced. If I push cut through them even with the sharpest polished push cutting edge, it will still take significantly more force than slicing/drawing the edge across them.

Slicing/cutting takes less force then chopping/cleaving.


We could see this effect with a rudimentary test cutting rope, if you take a thick piece of 1 inch manilla rope and cut it by pushing straight through it versus sawing the edge back and forth you will certainly notice the difference when the rope is that thick.


Even when they make electric knives, the blades are designed to move back and forth. Not chop up and down. Of course, that would be fun to see an electric knife designed to chop up and down, but I guess that would be more like electric scissors but missing the other half :P


Thank you for sharing your thoughts.

Empirical answer. Nice! Well done Shawn, strong work. Goes a long way toward answering the 'aggression' question, with a methodology to quantify. (Once those tomatoes are calibrated, that is.)

Thanks for this Shawn ! A very thorough response to the thread about edge agression.

Super interesting, thanks for posting Shawn. Maybe a dumb question, but is there a table or chart out there that shows which steels have large carbides and which are finer carbides?

vivi wrote: ↑

Mon Nov 20, 2023 9:48 am

So this topic has me thinking, maybe I'm not focusing on the steels themselves enough?

I would be curious of what you think about S110V with a coarse edge thinned out? If you haven't tried it, it may be an enjoyable steel to you.

Bolster wrote: ↑

Mon Nov 20, 2023 11:14 am

Empirical answer. Nice! Well done Shawn, strong work. Goes a long way toward answering the 'aggression' question, with a methodology to quantify. (Once those tomatoes are calibrated, that is.)

Thanks, I accidentally bought the organic ones instead of the "calibrated ones" Dang it

Ramonade wrote: ↑

Mon Nov 20, 2023 11:21 am

Thanks for this Shawn ! A very thorough response to the thread about edge agression.

Thank you. It would be interesting to explore more conditions.

Guts wrote: ↑

Mon Nov 20, 2023 11:33 am

Super interesting, thanks for posting Shawn. Maybe a dumb question, but is there a table or chart out there that shows which steels have large carbides and which are finer carbides?

Thanks for reading.

I haven't seen a table or charts but you could look at the micrographs of the steels here.

https://knifesteelnerds.com/2019/05/26/ ... ife-steels
You could also look at them in paper format in the book "Knife Engineering" by Dr Larrin on page 135.

Thanks Shawn, fascinating and informative as ever!

Awesome study Shawn!
Tomatoes are a great test medium methinks
I have a another test proposal:
Two Enduras: a k390 @~66HRC
and a ZDP-189 at similar hardness. Chromium carbides vs vanadium carbides. Both coarse and fine edge finishes.
I can provide said knives at your request.
Edit to add: I've got an Endura in 20CV for high carbide @ lower Rockwell if of interest as well

Sharp24/7 wrote: ↑

Mon Nov 20, 2023 2:54 pm

Thanks Shawn, fascinating and informative as ever!

Thank you, I appreciate the compliment.

Cycletroll wrote: ↑

Mon Nov 20, 2023 3:31 pm

Awesome study Shawn!
Tomatoes are a great test medium methinks
I have a another test proposal:
Two Enduras: a k390 @~66HRC
and a ZDP-189 at similar hardness. Chromium carbides vs vanadium carbides. Both coarse and fine edge finishes.
I can provide said knives at your request.
Edit to add: I've got an Endura in 20CV for high carbide @ lower Rockwell if of interest as well

Thank you! I think it would be more interesting to use the knife making and heat treating skills to make my own samples so we could see a wider range and test how the effects change.

Deadboxhero wrote: ↑

Mon Nov 20, 2023 4:10 pm

Cycletroll wrote: ↑

Mon Nov 20, 2023 3:31 pm

Awesome study Shawn!
Tomatoes are a great test medium methinks
I have a another test proposal:
Two Enduras: a k390 @~66HRC
and a ZDP-189 at similar hardness. Chromium carbides vs vanadium carbides. Both coarse and fine edge finishes.
I can provide said knives at your request.
Edit to add: I've got an Endura in 20CV for high carbide @ lower Rockwell if of interest as well

Thank you! I think it would be more interesting to use the knife making and heat treating skills to make my own samples so we could see a wider range and test how the effects change.

Agreed! :)
Just thought I'd offer

Erich wrote: ↑

Mon Nov 20, 2023 7:10 am

Ackerman's project revolved around how 440c was *cast* not 440c itself. He also constantly emphasized the need for this knife to be sharpened with very coarse grits as finer grits would nullify the "dendritic" teeth produced by the cast.

This is not a measure of carbide but rather how the knife is forged.

I fear you are missing the point, again, Erich. Shawn doesn't need to use cast 440C in his experiment, he just needs to use a known high carbide steel and compare it to a known low carbide steel to demonstrate aggression as an inherent component of the steel itself, in particular, the effect of carbides. As Shawn was careful to hold as many variables constant as he could, it's a valid demonstration that opens up a previously non-empirical (but intuited) dimension of steel performance to scientific empiricism. The variables that were not controlled (sharpness and hardness) should have benefitted the lower carbide steel (52100) but the opposite effect was found. Inventing a methodology to test, it's a clever demonstration of edge aggressiveness that Shawn could develop into a master's degree thesis, if he were so inclined.

Appreciate this, Shawn! Awesome info to learn amd study!

When I think aggression in my own personal collection, M4, K390, S90V, 15V(BBB heat treat) come to mind. When I was still new to knife steels, M4 was one of the first steels I ever noticed had an 'aggressive' quality that seemed different from other steels. It was kind of an intangible/unquantifiable, yet noticeable quality.

Great test! I love the cherry tomato as a testing medium but do acknowledge that any product of nature will have variance. I wonder if we could pool our collective experience regarding other materials that have shown similar properties of causing highly polished edges to "skate" to come up with a testing medium that is more uniform and hence enable controlling of that variable. First thing that comes to mind is plastic wrap. I'd gladly donate a big old roll of Costco cling wrap if it would further research in this area.

Again awesome job Shawn!

Bemo wrote: ↑

Tue Nov 21, 2023 10:08 am

Great test! I love the cherry tomato as a testing medium but do acknowledge that any product of nature will have variance. I wonder if we could pool our collective experience regarding other materials that have shown similar properties of causing highly polished edges to "skate" to come up with a testing medium that is more uniform and hence enable controlling of that variable. First thing that comes to mind is plastic wrap. I'd gladly donate a big old roll of Costco cling wrap if it would further research in this area.

Just for the sake of discussion, is a "skin," or other medium that causes a blade to skate, necessary for aggression testing? Would not depth of cut into a uniform medium (I'm thinking synthetic ballistic gelatin, or closed cell foam like a blue camping mat, or some other uniform solid) also serve as a possible medium? Because, if I understand aggression correctly, it shouldn't require a skin-like barrier to evince. Should get a deeper cut even in a uniform solid, no?

Throwing spitballs here, thinking of resistant materials, can't help but think of zip ties. Maybe number of sawing motions of a certain distance at a certain force to cut through a particular brand of zip tie?

Though if I'm wrong, and "skin" is necessary to show the effect, then yeah, a certain number of winds of cling wrap around, say, a round foam pipe insulator might provide a consistent medium. Though cling wrap isn't very "scate-y," is it? It punctures pretty fast in my experience. Wonder if there's a somewhat heavier wrap plastic. Aluminum foil might cause skate? Packing tape? Tomato skins are notorious, but what else (that's constant) causes blade skate?

silver skin.