Very poor edge retention when cutting cardboard

The hair-whittling, phonebook-paper-cutting level of sharpness will not last long cutting cardboard, and that seems to be true of super steels and mere mortal steels about equally. That last 5% of razor sharpness is not going to stand up very long under use, they all give it up fairly quickly.

Supersteels can retain a good working edge for much longer after losing that shaving sharpness, but the "paper trick" sharpness will disappear with just a little elbow grease and cardboard. Nothing to worry about. Just keep your Paper Trick Knife and your Cardboard Knife away from each other. Whatever you do. don't let them have kids together!

I've been buying a lot of hi-fi gear lately, and the people that make that stuff really know how to pack it for shipping. The cardboard boxes they ship in are so stiff that most knife blades will bind after a few inches. I broke out a box cutter and sharpened the blade, and soon found that is the thinking man's way to cut up a carboard box!
 
Khromo said:
I've been buying a lot of hi-fi gear lately, and the people that make that stuff really know how to pack it for shipping. The cardboard boxes they ship in are so stiff that most knife blades will bind after a few inches.
Click to expand...
This is exactly what I was thinking about when I started reading this thread. I picked up some Klipsch speakers a couple of months ago, and wow, they were packed in some tough cardboard boxes. It was tough going, even with brand new box cutter blades. I try to keep my knives sharp, but a very thin blade was essential for cutting up those boxes.
 
Triple_D said:
This is exactly what I was thinking about when I started reading this thread. I picked up some Klipsch speakers a couple of months ago, and wow, they were packed in some tough cardboard boxes. It was tough going, even with brand new box cutter blades. I try to keep my knives sharp, but a very thin blade was essential for cutting up those boxes.
Click to expand...

Some of those boxes were so tough that I started paying attention to cutting with the grain to make it easier! I gotta say, though, that speakers from France and Italy and electronics from Great Britain and Asia all arrived without a scratch!

As a buddy who used to sell them would say, "They're not cardboard boxes. They're corrugated containers."
 
I've had better experience with M390/20CV when to comes to cardboard. S30V and 154CM dulls a lot faster.
 
Wood products like cardboard and paper contain Silicates (SiO2). These are also found in abrasives like Arkansas stones (microcrystalline Quartz). I use Tungsten Carbide blades in my box cutters. They are harder than Quartz. Stay away from staples and don’t twist or drop the blades. They are quite brittle.
 
Cardboard is rough on edges. I have had good success lately by back stroking a sharpened edge on the diamond stone to pull the burr away. I have noticed longer cutting times and even back stroking will bring the edge right back.
 
One thing I could recommend is adding a 400 grit stone in there. There's a weird thing that happens sometimes when you jump between a coarse and fine grit. You'll end up with a burr that will sit down between the teeth on the edge. You can't even tell it's there. Adding another stone between grits will solve it, the other option is to spend a little more time on each stone after the 220. Can't say for sure that's what's happening here, but it's worth a shot.
 
Zenturio said:
...after a few meters of cardboard, the knife was extremely dull. Even had a microchip.
Click to expand...

My first impression was that you probably still had a burr. A cleanly formed apex should not chip on a few meters of cardboard, unless perhaps if the cardboard was extremely gritty/sandy.

A few questions, if I may...

Did you perhaps have a perfectly aligned burr that was invisible to detect?

How did you check for edge stability? One test I know of is to push-cut monofilament fishing line on a cutting board. If you have a burr it would fold over and leave a tiny dent/chip in that spot on the edge. A clean apex will not be affected by cutting fishing line.

Zenturio said:
After let's say 5-10 meters of cardboard the sharpness decreased to about 30% of beginning sharpness.
Click to expand...

Does it continue to cut cardboard or paper after that? Is your standard for sharpness perhaps too high?

In my experience I lose the hair-shaving sharpness relatively quickly, but it continues to cut cardboard for a looong time after that. For instance, I've been using a K390 Endela wharncliffe to cut boxes for home recycling for over a year. I can go 2-3 months between sharpenings before it stops gliding smoothly through cardboard. No stropping in that time. I run a 17 dps edge with a 20 dps DMT Fine (600 grit) micro bevel, which is quite obtuse!

K390 is the best performer on cardboard so far in my experience. The stuff is magical.



I also found this flashlight trick to spot a burr useful, especially when checking in a dimly lit room. Make sure you shine light from behind onto the edge on either side. Kindly ignore if you know this already.

 
Last edited:
Zenturio said:
I did also edge stability tests before the cardboard test to check for burrs and chips. All knives passed those tests (cutting through very hard wood, even with twisting into the wood and cutting/twisting through heavy zipties). All knives did not chip and did not lose any sharpness.
Click to expand...
In that case there is a big chance you have no burr on the edge.

Zenturio said:
Do I have problems with micro burrs or is the cardboard I got extremely abrasive?
Click to expand...
According to your hard wood test you should have no burr on the edge.

I would check Youtube. There are guys doing cardboard edge retention tests so you could get some numbers to compare with your results.
I watched a few videos from Outpost76 some time ago ... he was cutting cardboard and checking the edge.
Here is one of them:
 
The Spyderco Mule in HIC has been a game changer for cardboard processing in my garage. It's a very strange material and never really "feels" sharp if you're one to thumb your edge, but easily takes a paper slicing edge with resin bonded diamond stones. People over on Spyderco's forum have also had great success with diamond lapping films. Once I got it slicing paper I went to town cutting up boxes, and there has been no noticeable drop in performance in several months of cutting. I fill a 96 gallon recycling container every month or so with carboard cut into strips, usually 2-3" by 6-10" long and the knife just keeps on cutting. I haven't taken it to paper in a while but I have no reason to do so as long as it's still gliding through the cardboard. I don't think I'll ever go back to steel for cutting large amounts of cardboard.
 
Brock O Lee said:
Click to expand...

That flashlight trick is fantastic. Feeling a burr and seeing it are two completely different things. Great tip.

But here's my issue with it: I cannot get a burr that's too small for me to feel but that also shows up with a flashlight. Maybe my sense of touch is just really good. I don't know.

This is something that I am very interested to hear about from other people. Are you getting burrs that you can't feel with your thumb, but that will show up when you angle a flashlight beam across the blade?
 
Oh man, I just noticed.... in my previous post I attached the wrong link.
Here is Outpost76 cuting cardbord and counting how many feet till the knife does not shave arm hair.
 
Hi everyone,

huge thank you for the high amount of responses; I would not have imagined that :)

It's a little hard to quote every specific answer, so I will try to summarize my experiences according to the questions asked.

-After cutting a few meters of cardboard, the test knives lost their arm hair shaving sharpness completely

-After cutting a few meters of cardboard, the test knives were not able to cut telephonebook paper, but printer paper (not cleanly). So that is my consideration for a dull edge

-I know that the use of a box cutter (and maybe ceramics or other kinds of material/coated edges) makes much more sense, but sometimes I only have my folder in my pocket and do not want to walk to search for a box cutter; Also, I like the idea of using my EDC for every cutting task appearing

-A lot of people claim to be able to cut f.e. 300ft of cardboard before losing shaving sharpness (or high level sharpness); Cliff Stamp once told, that even a low wear resistant steel (f.e. 420) would be able to cut a higher amount of cardboard in order to decrase to 90% initial sharpness, if properly sharpened - That is something I was never able to achieve, but I am a very experienced sharpener as I told. It is hard for me thinking about doing something essential wrong the past 15 years

-A perfectly aligned burr could be possible, anyway I am not able to detect that

-My edge stability test is to make really hard cuts into dry firewood (birchwood), also with twisting the edge; After that I check for degradation. If the edge has no chips or rolls and still shaves cleanly, I will cut and twist through thick zipties. If the edge passes those tests, I cut through heavy polypropylene rope (2cm diameter). If nothing changes with the edge, I quote the edge as burr free and stable

-Maybe my understanding of working sharpness is not right. I find an edge which cuts printer paper quite cleanly has "working sharpness". I really only have troubles with quick dulling when cutting cardboard. I never had any serious chips/dents or fast dulling cutting other media; And I am quite rough with my knives (but I use them with brain, so no abuse happens to them).




-I will try following the next days
Using the knives right off the guided sharpening system (finishing with 1000# electroplated diamond, maybe stropping on leather with 5µm diamond)
Using edge trailing strokes
Using the flashlight method for visual burr detection (unusual and maybe problematic for me because I am working with microbevels mostly. Could be possible to think the microbevel is the burr and vice versa).
Using the guided system with diamond lapping film after the plates (I think I have them in 3000# or something). My problem is, that I like aggressive (coarser) edges most
Using Cliff's Plateau sharpening method again, but with a coarser microbevel grit (f.e. Norton crystolon fine). There should be no burr when using that Plateau Sharpening method

I am a little saddened because the Shaman is my all time favorite knife. I ordered a DLC S30V version a few days ago, didn't arrive yet. I would like to try M4 steel, but I would have to take that f.e. with the Tenacious, which I would have to order and send my Shaman back. But seeing the other people's results, even S30V should be able to retain a better working sharpness than I achieve with it. I guess there is something wrong in my process which I am not able to identify yet.

After the next sharpenings, I will try to make pictures through my 15X loupe. Maybe you can see something I am not able to see.


Long text, sorry. I want to thank you all again very much, it is well appreciated!

BR Oliver
 
I was just looking and reading about this HIC Mule. Interesting.
They say HIC is more tough as conventional ceramic yet not as tough as steel so there is no warranty against breakage. But they had to add this hole in the blade and compromise it.
Makes no sense. Makes me wonder what genious designed this knife. He sure was not a mechanical engineer.
 
I think there's a lot of great info here, but I'll second and add a little to it as I process a ton of cardboard each month and have a seperate knife specifically for that purpose.

1. Steel is key: I have never had great luck with S30V vs. Cardboard, so I started using a knife specifically for the purpose, which was something I learned in the kitchen having a 10" chef knife specifically sharpened and used for watermelon and canteloupe. For cardboard I started out with a blurple Spyderco Military in S110V (Did great!), and moved on to K390 and Maxamet, both of which are *FAR* better suited to cardboard destruction than S30V. I recently picked up a Mule team blade in Rex T15 that I've been using with great results as well.

2. Drop the micro-bevel. I sharpen my cardboard knives at 16 dps w/no micro. Unless you happen to hit a hidden staple I just don't feel the drop in cutting performance is worth the extra durability. Like I said earlier, I have specific knives that I use exclusively for cardboard and have NEVER chipped an edge. They may get dull, but I have yet to take any damage to the edge, and

3. Polish the bevel: This is something I tried just for fun and it did make a difference. Having more polish to the bevel allows the blade to slide through the cardboard much easier. True it will lose that stupid hair whittling sharpness quickly, but it will still be plenty sharp for the job.

Give those a try and let us know how it goes!

P.S. A HUGE Thank you to I Ilikesharpstuff for mentioning the H1C mule. I missed the drop, but checked back on the site when I read your post and they were in stock! I have one coming, and I'm really looking forward to trying it in the cardboard battle!
 
Have we thought about changing this website's name from BladeForum to BurrForum? There is a preoccupation with burrs over here that I don't see on other knife-related sites.

Maybe a few edge leading strokes would help. Works for a lot of guys.
 
Glock Guy said:
I think there's a lot of great info here, but I'll second and add a little to it as I process a ton of cardboard each month and have a seperate knife specifically for that purpose.

1. Steel is key: I have never had great luck with S30V vs. Cardboard, so I started using a knife specifically for the purpose, which was something I learned in the kitchen having a 10" chef knife specifically sharpened and used for watermelon and canteloupe. For cardboard I started out with a blurple Spyderco Military in S110V (Did great!), and moved on to K390 and Maxamet, both of which are *FAR* better suited to cardboard destruction than S30V. I recently picked up a Mule team blade in Rex T15 that I've been using with great results as well.

2. Drop the micro-bevel. I sharpen my cardboard knives at 16 dps w/no micro. Unless you happen to hit a hidden staple I just don't feel the drop in cutting performance is worth the extra durability. Like I said earlier, I have specific knives that I use exclusively for cardboard and have NEVER chipped an edge. They may get dull, but I have yet to take any damage to the edge, and

3. Polish the bevel: This is something I tried just for fun and it did make a difference. Having more polish to the bevel allows the blade to slide through the cardboard much easier. True it will lose that stupid hair whittling sharpness quickly, but it will still be plenty sharp for the job.

Give those a try and let us know how it goes!

P.S. A HUGE Thank you to I Ilikesharpstuff for mentioning the H1C mule. I missed the drop, but checked back on the site when I read your post and they were in stock! I have one coming, and I'm really looking forward to trying it in the cardboard battle!
Click to expand...

No problem, I think you'll enjoy it. They did a second run and surprisingly they're not selling very fast at all. The general consensus among the first drop was that while it is much improved over the white ceramic kitchen knives, it's not a replacement for steel or the future of knife making or anything like that. It will still chip if you hit a screw/staple/whatever, and I've seen a couple blades snapped from lateral force. People were/are having trouble getting them as sharp as they'd like. I've only seen one guy achieve shaving sharp, and he used diamond lapping films on a guided system. I used Venev resin bonded diamonds and got it to slice paper cleanly but not shave...I also didn't spend a ton of time on it but honestly it sharpened easier than I expected. Whenever it finally loses some performance I'm going to thin it out a few degrees and spend some time making sure it's fully apexed and I think it will just get even better. Even when it slices paper cleanly it doesn't "feel" sharp to the touch but it's a cardboard destroyer.
 
Zenturio said:
I am a little saddened because the Shaman is my all time favorite knife. I ordered a DLC S30V version a few days ago, didn't arrive yet. I would like to try M4 steel, but I would have to take that f.e. with the Tenacious, which I would have to order and send my Shaman back.
Click to expand...
For what it's worth, the Tenacious, and particularly the M4 version, is a much better cardboard cutting knife than the Shaman will ever be. It has much thinner blade stock and it's also ground much thinner behind the edge. Total cardboard slayer, that one. I have two of them, and also a Shaman in M4.
 
You must log in or register to reply here.
Back
Top