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Old 06-17-2017, 12:07 PM
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Why does paper dull knives/blades?


I have repeatedly heard that slicing paper with a knife is a sure way to dull that knife.

My question is why? How? Clearly the metal of the knife is far harder than the paper. So how can paper possibly have any effect on a metal knife?

Last edited by Whack-a-Mole; 06-17-2017 at 12:07 PM.
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Old 06-17-2017, 12:14 PM
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Paper contains clay and other hard minerals.
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Old 06-17-2017, 12:19 PM
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"We can see here in this scientifically accurate animation that each paper molecule uses tiny files to dull the knife blade."

No, I put this in the "myth" category. Yes, I know that other posters will argue this, but I will stand firm. Cutting ANYTHING tends to dull blades. The softer the material is, the less dulling effect. Remember, printers use (and have used) sliding knife blades to trim bound books and printed materials for hundreds of years. You will not ruin your knife or scissors by cutting paper.

On the other hand, my own sainted mother would chase us around the house if we used her sewing scissors to cut paper.
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Old 06-17-2017, 12:23 PM
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On the other hand, my own sainted mother would chase us around the house if we used her sewing scissors to cut paper.
My wife is the same. We have scissors for paper, scissors for cloth and some in the kitchen that I can use for anything from cutting chickens up to cutting plastic trays to make them fit the bin.
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Old 06-17-2017, 12:24 PM
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Paper contains clay and other hard minerals.
Yes, coated paper contains clay and some other materials, but I am thinking of basic, standard paper. Cutting sandpaper will also dull knives. The clay in coated paper is extremely fine...much finer than a typical sharpening stone. You might as well argue that cutting coated paper will actually improve the blade.
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Old 06-17-2017, 12:27 PM
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My wife is the same. We have scissors for paper, scissors for cloth and some in the kitchen that I can use for anything from cutting chickens up to cutting plastic trays to make them fit the bin.
True story...at the age of 101, my grandmother decided that there was excess electricity leaking around her house, so she cut all the electrical cords she could find with a pair of scissors. They looked like wire strippers afterwards, with half a dozen notches on each blade..
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Old 06-17-2017, 12:28 PM
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Originally Posted by ZonexandScout View Post
Yes, coated paper contains clay and some other materials, but I am thinking of basic, standard paper. Cutting sandpaper will also dull knives. The clay in coated paper is extremely fine...much finer than a typical sharpening stone. You might as well argue that cutting coated paper will actually improve the blade.
Nope.
A sharpening stone is used parallel to the edge, not perpendicular to it. Just see how fast you can wreck a knife edge with a sharpening stone used incorrectly.
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Old 06-17-2017, 12:33 PM
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On the other hand, my own sainted mother would chase us around the house if we used her sewing scissors to cut paper.
I hope none of you were holding the scissors.
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Old 06-17-2017, 12:38 PM
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Nope.
A sharpening stone is used parallel to the edge, not perpendicular to it. Just see how fast you can wreck a knife edge with a sharpening stone used incorrectly.
I'm still going to disagree. The clay is bound into the paper surface, which is being split by the scissors or knife blade to then pass parallel to the blade. The actual edge of the blade is not cleaving the particles. They are much too fine. This is not the same as trying to cut a rock.

Besides, the purpose of a blade is to cut, get dull, and be resharpened. If you don't do all three, the purpose is unfulfilled.
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Old 06-17-2017, 12:39 PM
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I hope none of you were holding the scissors.
Nope. We would have gotten a spanking for running with scissors for sure.
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Old 06-17-2017, 01:26 PM
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I have Fiskars scissors I use for cutting out my 4"x7" ebay shipping labels from plain stock non coated 8"x11" printer/copier paper and they are still going strong with no sharpening after slicing (conservatively) at least 5000+ sheets or (14+8 x 5000) 110,000 inches of paper over the years. Having said this the edges of each scissors blade are sharp"ish" but not razor sharp and might not be suitable for delicate textile work at this point while still being great for stiff sheets of paper. Horses for courses.

I also have several knives I use to slice up cardboard boxes for breakdown or shipping re-use and cardboard will absolutely beat the crap out of the edge of even the finest knife steel after even modest use.

http://so-sew-easy.com/cut-paper-with-sewing-scissors/ (the cartoon is amusing)

Last edited by astro; 06-17-2017 at 01:30 PM.
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Old 06-17-2017, 01:31 PM
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I'm still going to disagree. The clay is bound into the paper surface, which is being split by the scissors or knife blade to then pass parallel to the blade. The actual edge of the blade is not cleaving the particles. They are much too fine. This is not the same as trying to cut a rock.

Besides, the purpose of a blade is to cut, get dull, and be resharpened. If you don't do all three, the purpose is unfulfilled.
You can disagree all you want, but then you need to explain how scissors ever get dull if cutting is the same as sharpening.
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Old 06-17-2017, 01:36 PM
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Did anyone else notice, in that link, that their last cite, the one they considered the most definitive, was just a direct quote of their first cite?
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Old 06-17-2017, 01:36 PM
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I'm still going to disagree. The clay is bound into the paper surface, which is being split by the scissors or knife blade to then pass parallel to the blade. The actual edge of the blade is not cleaving the particles. They are much too fine. This is not the same as trying to cut a rock.

Besides, the purpose of a blade is to cut, get dull, and be resharpened. If you don't do all three, the purpose is unfulfilled.
By that logic, diamond dust in saw blades would do nothing, and yet we know that it does.
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Old 06-17-2017, 01:40 PM
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You can disagree all you want, but then you need to explain how scissors ever get dull if cutting is the same as sharpening.
But I didn't say that. I said that "you might as well argue...." Cutting anything at all will dull the blade. You are absolutely correct that cutting coated paper will not sharpen a blade.

Blades get dull. That's to be expected. But to say that cutting paper is a lot worse than cutting anything else (meat? bone? rope?) is just not accurate. What are you SUPPOSED to cut with knives?
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Old 06-17-2017, 02:05 PM
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Originally Posted by ZonexandScout View Post
But I didn't say that. I said that "you might as well argue...." Cutting anything at all will dull the blade. You are absolutely correct that cutting coated paper will not sharpen a blade.

Blades get dull. That's to be expected. But to say that cutting paper is a lot worse than cutting anything else (meat? bone? rope?) is just not accurate. What are you SUPPOSED to cut with knives?
This was the question:

Why does paper dull knives/blades?

I never said that cutting paper was worse than cutting other materials, but it's probably pretty bad, at least compared to fabric or hair. When I cut mats, I do one-cut per edge with my mat cutter (it uses single-edge razor blades). So, it takes me two blades per mat. But, if I don't, the edges don't come out perfectly smooth (they get tiny tears at the edges). Note: the edges cut in mat board using this method are as sharp as a knife!

Last edited by beowulff; 06-17-2017 at 02:06 PM.
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Old 06-17-2017, 02:07 PM
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<Peter Lorre voice> It always surprises me how fast human tissue dulls a scalpel blade. </PLV>
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Old 06-17-2017, 02:24 PM
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I have no idea if paper dulls knives faster than other common substances but I'll point out that paper cutters and scissor are honed differently than most knives. They have a chisel edge, flat on one side and less taper. Those blades are not meant to flex at all and most knives are. Paper cutters will also be made of harder steel and so are many modern scissors because no lateral force is expected to be exerted on them.
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Old 06-17-2017, 02:34 PM
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I have no idea if paper dulls knives faster than other common substances but I'll point out that paper cutters and scissor are honed differently than most knives. They have a chisel edge, flat on one side and less taper. Those blades are not meant to flex at all and most knives are. Paper cutters will also be made of harder steel and so are many modern scissors because no lateral force is expected to be exerted on them.
Good point. Using my rolling photo cutter is different from using my pocket knife, for exactly that reason. I hardly ever sharpen (or replace) the wheel on my photo cutter.
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Old 06-17-2017, 02:51 PM
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I run a dog grooming salon, and I spend hundreds of dollars a month keeping sharp scissors for my groomers. If I see anyone cutting paper with their scissors, there will be some retraining on proper equipment use going on in fairly short order. (I have two pairs of paper scissors around for the times when paper needs to be cut.

The point is, is that paper will not dull knives or scissors all that much, but it will dull them. You will not notice the effect if you use these scissors to cut paper all the time, as paper is not that hard to cut.

But, when you go to cut something else with those scissors, you will notice that they are duller.

Scissors for things like cutting hair are razor sharp. If you only cut clean hair with those scissors, they will stay that sharp for a good while.

Cutting other things, like paper or dirty hair with those scissors will dull them significantly faster. You would still be able to use them to cut paper, but their razor edge that is useful for hair will be too dull, and will bend the hair in between the blades rather than cleanly slicing it.

Also, scissors for hair cutting and other uses that need a razor edge are not cheap. I pay between $200-$500 for a single set of scissors. I paid about $5 for a pack of two paper scissors at office depot.

Use paper scissors for paper. Use the expensive razor sharp scissors for their intended purpose.
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Old 06-17-2017, 02:58 PM
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I run a dog grooming salon, and I spend hundreds of dollars a month keeping sharp scissors for my groomers. If I see anyone cutting paper with their scissors, there will be some retraining on proper equipment use going on in fairly short order. (I have two pairs of paper scissors around for the times when paper needs to be cut.

The point is, is that paper will not dull knives or scissors all that much, but it will dull them. You will not notice the effect if you use these scissors to cut paper all the time, as paper is not that hard to cut.

But, when you go to cut something else with those scissors, you will notice that they are duller.

Scissors for things like cutting hair are razor sharp. If you only cut clean hair with those scissors, they will stay that sharp for a good while.

Cutting other things, like paper or dirty hair with those scissors will dull them significantly faster. You would still be able to use them to cut paper, but their razor edge that is useful for hair will be too dull, and will bend the hair in between the blades rather than cleanly slicing it.

Also, scissors for hair cutting and other uses that need a razor edge are not cheap. I pay between $200-$500 for a single set of scissors. I paid about $5 for a pack of two paper scissors at office depot.

Use paper scissors for paper. Use the expensive razor sharp scissors for their intended purpose.
I totally agree. Hair is actually a lot easier to cut and, therefore, less dulling. The same applies to a razor. Woe unto the person who uses my (beard) razor to shave his/her legs.

But, to get back to basics, the original question was (paraphrased), "Of all things you can cut with a knife, does cutting paper dull them significantly more than the others?" I maintain that the answer is, "No."
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Old 06-17-2017, 03:10 PM
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Yes, coated paper contains clay and some other materials, but I am thinking of basic, standard paper. Cutting sandpaper will also dull knives. The clay in coated paper is extremely fine...much finer than a typical sharpening stone. You might as well argue that cutting coated paper will actually improve the blade.

Conversely the internet suggests cutting sandpaper as the prime way to sharpen scissors.

WikiHow



Never sharpened scissors personally, so no idea...
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Old 06-17-2017, 03:23 PM
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I totally agree. Hair is actually a lot easier to cut and, therefore, less dulling. The same applies to a razor. Woe unto the person who uses my (beard) razor to shave his/her legs.

But, to get back to basics, the original question was (paraphrased), "Of all things you can cut with a knife, does cutting paper dull them significantly more than the others?" I maintain that the answer is, "No."
Yeah, i got off track talking about scissors. I also have extensive experience with knives, having spent nearly 20 years in kitchens before an abrupt career change.

Good kitchen knives are also honed to be razor sharp. When you spend several hours a day cutting things, having a sharp knife makes a huge difference on the wear on your wrist. Using the cheap house knifes was probably going to give me arthritis or carpal tunnel, so I got some wusthofs instead. (You can also create a better presentation with sharp knives, allowing thinner and more accurate cuts.)

Foods like meats, fruits, and the "vegetables" that are actually fruits usually contain very little in the way of hard minerals, though actual vegetables (the plant parts of a plant) contain cellulose and other fibrous material that can do a bit more dulling on the blade, but still not that much.

Cutting other things, like paper, that has hard minerals in it will dull the blade much faster than meats or fruits.

Now, I am sure there are other things you could try to cut that would dull the knife faster, but if the question is simply, will cutting paper dull a knife faster than meats and fruits (and cheese for that matter), then I am pretty sure the answer is "yes".
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Old 06-17-2017, 03:27 PM
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Conversely the internet suggests cutting sandpaper as the prime way to sharpen scissors.

WikiHow



Never sharpened scissors personally, so no idea...
Yeah, scissors with a beveled edge that just needs to be put back into hone will find improved cutting after cutting through sandpaper.

That is because the sandpaper will remove and burrs or other blemishes along the blade.

You would get better improvement from properly honing them, and that technique would utterly destroy good scissors.
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Old 06-17-2017, 04:26 PM
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Re my notes and the notes of others here are certain scenarios where scissors have to be their sharpest to work properly (hair, fine textiles etc) and even a minute step off that level yields unusable scissors other scenarios like cutting copy paper in my example you can keep using "sharp enough" scissors very satisfactorily for years.

If you use a pair of "must be sharpest" scissors for paper cutting they will rapidly degrade to "sharp enough for stiff paper" which is useless for hair cutting here the scissor needs to glide through hair very quickly.
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Old 06-17-2017, 07:07 PM
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The answer is that soft materials can erode hard materials. We know that flowing water can erode rock, so why is it a surprise that paper can erode steel?

It doesn't take much to dull a knife. The edge of a sharp knife is very fine—it's actually the fineness that makes it sharp. Because of this, you don't have to remove much metal to turn a sharp knife into a dull one.

Another thing that causes knives to go dull is for the edge to roll over (rather than for it to be eroded away). This is why steeling a knife keeps it sharp: the steel straightens up the edge. Again, since the edge of a sharp knife is so fine, it doesn't take much to distort it. The material being cut doesn't have to be harder than steel for it to roll the edge over.
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Old 06-17-2017, 11:51 PM
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I'll mess with your minds:

How is a "sharpening" "steel" used?

The steel is that rod you see fine chefs use on a knife just before using it.

Different blade designs are used, depending on intended use.

I have a pair Barber's shears (not "scissors"). The instructions with them were quite specific:
"Never use these shears for anything but human hair".

The chef's knives do not dull in the same manner as an axe or common scissors - the edge folds over - the steel is used to push the edge back in place. Using the steel as a sharpening stone will ruin the blade pretty much instantly.

Ever see a sign stating "We sharpen knives"? No sharpening stone for them.

I have both a guillotine type paper cutter and a rolling paper trimmer.

Paper is a special case. I'm guessing the way the fibers will stretch instead of simply shearing into two.

Last edited by usedtobe; 06-17-2017 at 11:51 PM.
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Old 06-18-2017, 04:08 PM
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On the other hand, my own sainted mother would chase us around the house if we used her sewing scissors to cut paper.
Amusing story there, now we know how you got your shawnee name runs with scissors
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Old 06-18-2017, 05:19 PM
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The answer is that soft materials can erode hard materials. We know that flowing water can erode rock, so why is it a surprise that paper can erode steel?
I've tried arguing exactly that point here before to no avail. It seems to be the overwhelmingly popular view that if you have two different materials of different hardnesses in contact, the softer one experiences all the wear, and the harder one experiences none at all. (And that the wear exerted by wood upon hardened saw blades is the result of contamination by hard mineral particles - likewise water upon rock, or chemical reaction or process).

But it seems entirely reasonable to me that the differential hardness means there should be differential distribution of wear, not just all of the wear falling on the softer material.
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Old 06-18-2017, 06:12 PM
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I'm still going to disagree. The clay is bound into the paper surface, which is being split by the scissors or knife blade to then pass parallel to the blade. The actual edge of the blade is not cleaving the particles. They are much too fine. This is not the same as trying to cut a rock.

Besides, the purpose of a blade is to cut, get dull, and be resharpened. If you don't do all three, the purpose is unfulfilled.
You're saying the clay doesn't help dull the edge? Well it does, along with the paper fiber itself. Do you know what plant fiber is made of? Calcium carbonate, calcium oxide, sometimes a little silica (the ash part after burning.) That will definitely dull steel. And it takes only a little cross-contract with the cutting edge to dull it. The real cutting happens on the first .005 millimeters of the cutting edge. The rest is just side friction.

As to our mothers' insistence that paper will dull scissors faster than cloth, it's probably not true (my opinion) as they're made of roughly the same substance minus the clay coat. It's constancy of use. A housewife doesn't really cut cloth all day, unless she makes dresses as a business. In which case the scissors will really get dull.

I'm into knives so I kinda know how to sharpen scissors. The old rules no longer apply in our house.

Last edited by Marci Al; 06-18-2017 at 06:15 PM.
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Old 06-18-2017, 08:01 PM
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Originally Posted by ZonexandScout View Post
"We can see here in this scientifically accurate animation that each paper molecule uses tiny files to dull the knife blade."

No, I put this in the "myth" category. Yes, I know that other posters will argue this, but I will stand firm. Cutting ANYTHING tends to dull blades. The softer the material is, the less dulling effect. Remember, printers use (and have used) sliding knife blades to trim bound books and printed materials for hundreds of years. You will not ruin your knife or scissors by cutting paper.

On the other hand, my own sainted mother would chase us around the house if we used her sewing scissors to cut paper.
Most scissors don't have knife blades.
Professionals (including printers) sharpen their knifes as required.

And,
Your mothers scissors were probably a lot softer than a paper knife.
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Old 06-18-2017, 08:18 PM
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I have no idea if paper dulls knives faster than other common substances but I'll point out that paper cutters and scissor are honed differently than most knives. They have a chisel edge, flat on one side and less taper. Those blades are not meant to flex at all and most knives are. Paper cutters will also be made of harder steel and so are many modern scissors because no lateral force is expected to be exerted on them.
Also, scissors will work reasonably well even when not sharp, on many materials, simply by shearing rather than cutting. Scissors don't work (or don't work entirely) by simply being two sharp knives working from opposite sides. They work in part by forcing the material in two different directions ie placing it in shear.
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Old 06-19-2017, 03:43 AM
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Also, scissors will work reasonably well even when not sharp, on many materials, simply by shearing rather than cutting. Scissors don't work (or don't work entirely) by simply being two sharp knives working from opposite sides. They work in part by forcing the material in two different directions ie placing it in shear.
Indeed - and in that respect, they function best when the mating faces are a close fit (i.e. either nice and flat, or non-flat, but precisely matching.
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Old 06-19-2017, 04:25 AM
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As long as they shear against each other throughout the length, they will cut. Explains why pruning shears are often bent. It makes shearing more continuous. Straight blades tend to diverge from each other.

Also, whether for scissors, knives, or shears, material that's softer than the blade steel also causes dullness because they tend to coat or wrap around the very edge of the blade. Relatively easy to fix through a light touch-up by someone who knows blades.
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Old 06-19-2017, 11:43 AM
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Great discussion, but I'll make this my last post to the thread.

IMHO, it is a myth that cutting paper dulls a knife blade significantly more than cutting string, rope, or many other materials. Obviously, cutting anything that is harder is going to dull a blade faster than cutting something that is softer. But paper does not have some magical blade-defeating powers that will ruin your knife the second they touch. Paper is just "stuff," and cutting "stuff" dulls knives. When I cut paper using a ruler and my knife, the surface I'm cutting ON has a lot more effect than the paper itself.

In my experience, many people are told that cutting paper will dull a knife (or a pair of scissors) excessively and so "rules" are put in place to prevent it. Whether they are justifiable rules or not is up for discussion. In my experience working as an electrician who cuts up insulation, copper wire, cardboard, paper, tape, cloth, rope, string, sheetrock, and wood with my Kershaw, cutting paper is the least of my worries.
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Old 06-19-2017, 11:48 AM
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I'd guess this started from the concept of "Don't use my knife/scissors that I only cut hair/cloth/meat/whatever with to cut anything else", and the anything else was usually paper.
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Old 06-19-2017, 12:14 PM
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The answer is that soft materials can erode hard materials. We know that flowing water can erode rock, so why is it a surprise that paper can erode steel?
Flowing water erodes rock as it contains sand, etc- of harder rock.
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Old 06-19-2017, 12:26 PM
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Flowing water erodes rock as it contains sand, etc- of harder rock.
Or dissolves the rock. Or erodes it through impact, like with falling rain or waterfalls, or splashing, and through pressure to some degree. But without carrying other substances it is a very slow process. The materials carried by water that erode don't have to be harder than the rock to erode it, but a lot of it will be. Quartz and aluminum oxides are very hard and abundant, and fragile as well so likely to be broken into fine material carried by water.
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Old 06-19-2017, 02:23 PM
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I totally agree. Hair is actually a lot easier to cut and, therefore, less dulling. The same applies to a razor. Woe unto the person who uses my (beard) razor to shave his/her legs.
What do you think it being cut when someone shaves their legs??
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