Cardboard cutting; Steel vs. Geometry

I recently recorded a test where i cut cardboard with a kershaw leek and a benchmade valet while testing the sharpness by slicing a paper towel without shredding it. The leek went through the cardboard much easier and made much straighter cuts due to its thin blade and good edge geometry. The Valet was more difficult to get through the cardboard and it didn't cut as straight due to its less than ideal geometry for cutting cardboard. However, in the end, even though the leek was still getting through the cardboard easier, the valet with m390 maintained its razor edge for more cuts and was still able to somewhat easily shave hair off my arm. The leek could still shave hair off my arm but just barely. in my test of cutting 3 inch lengths of cardboard sourced from the same box, the leek did somewhere around 70 cuts and the valet did somewhere around 100. As far as cutting the cardboard goes, i would say the leek passed through it and the valet wedged it apart.
 
The only thing I have to add is a correction to the Landes quote. "Geometry cuts, HEAT TREATMENT (not the steel) determines how long". In cutting performance, geometry is the biggest factor. Second is a solid heat treatment. A distant third is the actual steel ID.
 
I disagree with the above. In the statement, geometry then steel, I think one can infer that heat treat is considered when listing the steel as it will be a property of that particular steel on the knife. Assuming you have two knives with the same exact geometry, one is 440a and the other m390 and they are both very well heat treated to 59, the m390 should most definitely out cut the 440a.
 
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Most of my thinnest blades cut cardboard the longest but the way I sharpen them also makes a difference.

Maxamet is probably my favorite for cardboard with a thin slicer.

An aus8 with a really thin profile requires multiple sharpenings when cutting up boxes over the mule team maxamet which isn't as thin a profile. So steel def makes a difference, but its variable.
 
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weeping minora said:
I recently found VG10 (Delica) to stand up better in EDC cardboard cutting in comparison to S30V and even XHP (both in the Manix 2 format).
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I'd attribute these findings moreso to the geometry, rather than the steels themselves.
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I agree with your conclusion.

One of the reasons that rope cutting is a better test of steel performance than cardboard is that during the cutting, the fibers pull back from the blade as they are cut. This means that edge angle is important, but the impact of overall geometry of the blade is greatly lessened. If you then control the edge angles of the knives being used, you end up with a test whose outcome is highly dependent on the alloy/heat treat properties.

Of course you can also tweak the outcome of rope cutting a bit, also.
♦ Slicing cuts produce results which are more impacted by wear resistance
♦ Push cuts produce results which are more impacted by hardness.
 
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microtech85 said:
Hey FortyTwoBlades, would you please elaborate? What do you mean by specific steel designation?
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The general category of steel that is used is of greater importance than the specific steel. As in shock-resistant steels, high carbide steels, highly corrosion-resistant steels, extremely fine-grained steels, etc. rather than specifically L6, S110V, H-1, AEB-L, and so on. So long as the steel is one that is reasonably well suited for the tool's intended use, that's more important than it being one particular kind of steel.
 
I agree that the overall category of the steel can be a better way to make a knife selection than choosing a specific steel. Because even if s30v may out cut s35vn, it would be barely perceivable to the user. These days i am ascribing more importance to the geometry of the blade and edge stability rather than outright edge retention. And of course, it all depends on what you intend to do with the knife. Right now i am really preferring 14c28n and m390 over most other steels. Also, s90v for some interesting characteristics such as aggressive cutting edge which happens to be great for fibrous materials such as cardboard; even as it dulls, it continues to cut well.
 
Just for fun, take a knife, preferably one you don't care much about, and keep sharpening and cutting cardboard. Each time, sharpen at a more acute angle than before. See how low it goes before the edge fails.

For more fun, use the coarsest grit that will give an arm shaving edge. I've gone as low as a Norton 220 grit water stone and 7 degrees per side. Cuts cardboard forever. I took a cheap ($7) blade of unknown stainless to 12 dps with a micro bevel at 15 and cut a kilometer of cardboard and it would still slice notebook paper. That was with a Spyderco medium grit ceramic edge.

I tend to agree with Samurai Stu. If you shape it properly, and give a good beast treatment, even 1055 will cut for a LONG time in cardboard.

I tend to disagree with Knarfeng, in that I think there can be binding in rope cutting, unless there is tension in the rope, and that it can be all but eliminated when cutting cardboard.
 
The geometry makes the cut, the steel and the heat treat should be chosen to optimize the geometry.
Then you will find what you are looking for.
 
dkb45 said:
The perfect example of geometry importance is box cutter blades. Even when dull enough to safely be ran across skin they can zip through cardboard like nothing. A fresh blade cuts a lot better, of course, but a dull box cutter actually can hold its own against something like a Medford (they are just synonymous with sharpened bricks).
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While this is true, it doesn't really prove anything. You can't compare two extremes like that and expect to gain any useful info.
If the question is "do I need a supersteel for my use?" then the answer is most folks won't notice a measurable difference.
If the question is "Is this steel more (wear resistant, tougher, harder, etc) than this other steel?" then the answer will be measurable and provable.
These are not the same question, and yet they seem to get treated the same. If all you do is cut cardboard, then thin might be all you need. But for a GP blade, you might need to consider using a high end steel to enable that super thin blade to do what you want to.
 
Responding to me2, i really like the way a blade comes off of the spyderco brown ceramic. It is somewhat refined and somewhat aggressive. A very nice finish to end with. I also like to do a few passes on each side with the spyderco fine ceramic. It refines the edge a little without removing the aggressive cutting edge.
 
gadgetgeek said:
While this is true, it doesn't really prove anything. You can't compare two extremes like that and expect to gain any useful info.
If the question is "do I need a supersteel for my use?" then the answer is most folks won't notice a measurable difference.
If the question is "Is this steel more (wear resistant, tougher, harder, etc) than this other steel?" then the answer will be measurable and provable.
These are not the same question, and yet they seem to get treated the same. If all you do is cut cardboard, then thin might be all you need. But for a GP blade, you might need to consider using a high end steel to enable that super thin blade to do what you want to.
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While it is an obviously extreme example, it does give credence to the fact that geometry is far more important than the steel used. With obvious exceptions to garbage steel like 420j2, pretty much anything higher than 440A will start to perform exponentially better with optimal geometry, and start creeping towards or even exceeding a super steel blade with garbage geometry, or even just a better steel with the same garbage geometry.
 
dkb45 said:
While it is an obviously extreme example, it does give credence to the fact that geometry is far more important than the steel used. With obvious exceptions to garbage steel like 420j2, pretty much anything higher than 440A will start to perform exponentially better with optimal geometry, and start creeping towards or even exceeding a super steel blade with garbage geometry, or even just a better steel with the same garbage geometry.
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I'll agree to that, what I'm disputing is this notion that seems to have flared up that there is no benefit at all to a higher end steel. I know that wasn't the summation of your argument, It was others who muddied it up more.

I would even go so far to say that while geometry is factor one, the overall percentage of the whole that can be attributed to the steel composition can narrow the gap in the comparison. For example, lets say we have knife A that has ideal geometry and a steel that is 25% as good as a theoretical perfection. Then you have knife B which is 90% of ideal in geometry, but the steel is much better. At some point, even though A starts out better, it will fall below the performance level of B. How much that gap becomes measurable would depend on the steel of B. Lets say that if the B knife has 40% ideal steel they become equivalent, then every increase in the steel will become more significant. These numbers are just for illustration, but hopefully they paint the picture.

I think its clear enough that a higher end steel can be pushed farther as far as geometry goes. I also am beginning to think that the whole idea of a cardboard cut test is a little silly since its pretty clear that geometry becomes over weighted in the grand scheme of things, and its overall utility as a representation of normal use is very limited. As a medium for controlled abrasion testing of a steel, then by all means, but due to its pretty poor tensile strength, the geometry just adds too much noise to the equation.
 
I think I should make it clear that I think Gaston and his points are not only unfounded, but also laughably incorrect. I've seen first hand how blood great super steels are. My Cru-wear Manix and K390 Urban have shown alone that there are steels that just make normal steels like even D2 look like garbage, which in their own right are not bad steels at all. I did some very unscientific testing with some cardboard cutting, and despite cutting around 50% more than S35VN, my Cru-wear Manix was just had the slightest diminish to edge sharpness.
 
Its sometimes hard to get an idea across clearly without a wall of text, and its likewise hard to keep track of who believes what. Back on the same page.
 
Considering that geometry is important for "cutting"...and that superior blade-steels have better edge retention than "lesser" steels...it seemed reasonable to choose CPM-20CV for my "casual-use" EDC. Also, I chose to have the blade reground to 3/32" max spine, with 0.010" max behind the edge, and with a high hollow grind. I will be excited to see it come to my mailbox...
 
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dkb45 said:
I think I should make it clear that I think Gaston and his points are not only unfounded, but also laughably incorrect. I've seen first hand how blood great super steels are. My Cru-wear Manix and K390 Urban have shown alone that there are steels that just make normal steels like even D2 look like garbage, which in their own right are not bad steels at all. I did some very unscientific testing with some cardboard cutting, and despite cutting around 50% more than S35VN, my Cru-wear Manix was just had the slightest diminish to edge sharpness.
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Emphasis on laughably.
 
I can cut cardboard all day with piece of tin from canned beans .What I learn in my short knive adventure is this ........The more carbides you have in your steel, you need something to keep them in place on the cutting edge . And ideal for that is convex edge geometry .


“Geometry cuts. The steel determines for how long” - Roman Landes
 
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