I might have come to the end of my super steel lust

[Popsickle]

also... i noticed chipping awhile back on my 20cp para too..... wasn't happy

[Lagrangian]

I think most modern steels are highly optimized. My guess is that for a given cost, they've pretty much achieved as much edge retention, toughness, and corrosion resistance as possible. I don't mean this exactly, but in broad general terms.

At this point, there is no free lunch: If you increase the hardness (which often improves edge retention), then you lose some toughness, and/or you lose some corrosion-resistance.

Modern steels seem to show some of this: The super-corrosion resistant steels do not have good wear resistance. The super-wear resistant steels are not tough as the toughest steels. And the toughest steels are not as hard or corrosion resistant as the best steels in each of those separate categories.

This doesn't mean that there are not advances that improve all of these qualities, but I think that such advances are difficult. For example, from what I understand, powdered metalurgy was a huge advance in both toughness and wear resistance, while presumably, leaving corrosion resistance roughly the same.

I think most steels that are used above 60 HRC or so, are probably optimized for wear-resistance, and so have traded off some toughness. Very very hard materials are often brittle (not tough), and so chip. I think this is what you're seeing with 20cp.

I'm no metallurgist or material scientist. So if you have a better understanding, please chime in.

Sincerely,
--Lagrangian

P.S. I haven't had a chance to try 20cp/s90v. But so far, I'm very impressed with M390. I would also like to try M4 and 3V sometime. I've always been a little fascinated by M4, which is a high-speed tool-steel that is optimized to cut steel in metal work and machining.

[Ankerson]

Ever since i joined this forum i've been on this quest for a higher end steel. I've tried a lot of the current offerings, but the main diet has been VG10, S30V, ZDP-189 and the latest which is CTS-20CP. The primary thing i cut is usually corrugated boxes, and i've found that most steels i can use through one shift at work and dull down to the point where they won't really slice printer paper anymore.

Which brings me to this 20CP stuff. I sharpen it to 36 degrees inclusive with a pretty low (25ish) back bevel. Lately i've noticed some chipping issues, which is something that annoys the hell out of me. I've always said that a chipped edge is better than a rolled edge because it will still cut...but man i'm getting sick of honing out chips. I really don't feel that 36 inclusive is asking too much....is it? I'm not the most gentile knife user..i'm usually working fast and when i cut a box down, it gets ripped through pretty aggressively.

So far i've blamed the chipping on how hard i use the knife, but i'm open to thoughts on it. Tonight i set the primary edge to 42 degrees inclusive on my Edge Pro. I've never really been fond of thick edges, and i consider 40 to be as thick of an edge as i like to go with, but i'm playing it safe and just sticking to the 22 degree setting on my EP and i'll see how it goes from here. The main thing that concerns me is the longevity of the knife, because i can already tell i've sharpened into the blade quite a bit more than i have on my DLC Para 2, and i carried that knife for a lot longer than i've had the 20CP. If i'm constantly sharpening out chips, i'm worried it's going to shorten the lifespan of the knife.

So now i've come to a crossroads where i'm asking myself if chipping is an acceptable nature of the beast when dealing with these kinds of steels. The edge retention is pretty amazing...i can still easily slice phone book paper after a day of work, but i'm way too much of a perfectionist to leave those chips alone so i find that despite the increased edge retention, i'm sharpening this knife at the end of every day anyways just like i would be with VG10.

Thoughts? Oh, and as for the edge as it is now, it's practically a convex edge since i have 3 bevels happening at the same time and they've all been stropped out pretty smooth.

Cardboard is very abrasive and depending on what is being cut exactly it can and will have various things embedded that can really damage edges.

So as you said the blade is still sharp after a days work so my recommendation is to just leave it and touch up as needed to maintain a working edge.

Also a coarser edge like around 600 grit off the EP or so or even off the brown stones off a Sharpmaker would be fine.

[Evil D]

So you paid $220 for a knife that you're gonna trash at work on cardboard and that you have to fix up and resharpen every night ? That's just silly. Why wouldn't you just use a knife that costs half that price (or even less) for all the grunt work and save the fancy one for more appropriate tasks ?

It's your money and your choice. But for what you're doing to your knife , you're just better off with a knife that costs @ $120 less with S30V , 154CM or VG-10.

Well, because cutting cardboard all day IS appropriate EDC tasks in my world. What else would i do with this knife? We're not talking about some custom damascus/mammoth ivory one of a kind knife here. I just don't see the logic of buying a $220 knife that i cut loose threads and open mail with. I may not be hauling lumber in my Lambo, but i'm sure as hell taking it to the track and racing the wheels off it like the manufacturer built it for

Anyway, thanks for the input everyone, i'll let you know how the 42 inclusive goes. At this point i'm still blaming rough usage but we'll see. I don't do any more cutting than Ankerson did in his test of 20CP vs. S90V, but i'm sure how methods of sharpening differ and i didn't have near as much chipping as he had, though the chips i'm getting did look to be a little worse than the ones he had, only fewer in number. Oh, and i'm certain i haven't hit staples or dinged the edge on anything, and i never cut against anything "cutting board" style, i'm usually holding what i cut in my off hand and slice in mid air.

[Ankerson]

One day it will look like this if you keep using it to cut cardboard..

[Cliff Stamp]

Large enough i can see them with the naked eye.

Based on the size it doesn't appear to be the steel itself fracturing as much as the edge just coming apart, this is likely simply due to the high volume of carbides and basically all you are seeing is the result of aggregates. In these PM steels the primary carbides are only a few microns in size but when they cluster in an aggregate this can be more than 10 microns easily. If the edge intersects one of these large aggregates then it is very likely going to end up as a weak point which will get rough as the carbide pops out of the edge. This is made even more dramatic if you hone to a very high polish and level of alignment (i.e. sharpness) and have a very low angle.

These steels in general are not really meant to keep this kind of edge - extremely fine and smooth cutting, they are made to cut that type of material well (cardboard) but generally do so at a low to moderate level of sharpness which they can keep on that material for a very long time. I would ask the question as to is this really the steel that will give you the performance you are looking for and I would think that AEB-L, or maybe even 19C27 would be more suitable. These will of course not have that long lasting edge retention with that rougher edge as they don't have the carbide volume to give the high wear resistance. But the edge composition is much more stable so they won't develop aggregate spots.

I do find the notion not to use the knife a bit odd, what else is it made to do. The only thing I would recommend is trying to stagger the cut contact point to make the wear a bit more even if possible. Note in regarding the angle, you only need to increase it

-wear you use it most (the base)
-just about half the depth of the chips (so it is a micro-bevel)

If you micro-bevel at 25-30 dps, but keep the micro-bevel very light as in just a few passes per side it will likely stop the aggregate wear and I doubt you could notice a significant loss in cutting ability as the bevel would be so narrow. You just need to make sure to work the primary angle to keep the micro from thickening.

[jackknifeh]

Well, because cutting cardboard all day IS appropriate EDC tasks in my world. What else would i do with this knife? We're not talking about some custom damascus/mammoth ivory one of a kind knife here. I just don't see the logic of buying a $220 knife that i cut loose threads and open mail with. I may not be hauling lumber in my Lambo, but i'm sure as hell taking it to the track and racing the wheels off it like the manufacturer built it for

I agree with Wolverine666 100% on this. That's because I'm not loaded with $220 lump sums of money. I also agree with you 100% on this. I like agreeing with your thinking more. It's just more fun. The first "work knife" I bought was the Manix2 with M4. Getting dirty and possibly scratched or dinged a little is part of that type of work. Lord knows my body gets scratched and dinged from time to time. It took a while before I was comfortable with breathing hard on the Manix though. So I was thinking I got this for hard work (when absolutely necessary ). If I don't use it for that I wasted my money. All $153.95 plus shipping of it. It still took a while but now I get it dirty and use it. If I'm working so I might have to do something that a folder may get damaged a little I use a Ka-Bar fixed blade. Other than that I use it for things that might destroy a Spyderco Bug. Or a Delica.

Having said that I still have a hard time getting any other expensive knife dirty or scratched. But, that's life I suppose.

Jack
PS edit: Oops, I got the name wrong at first.

[Jet B]

Just yesterday, I handled a Spyderco Persistence for the first time. I was really impressed with the quality of this knife for what it cost.

My suggestion would be to buy a couple of these value folders and take them both to work. When one gets dull through the day, just pull out the other one. If that Chinese steel is similar to AUS 8 then it might last half a day and it likely won't chip. You could touch them both up very fast at the end of your day.

Maybe mix it up and get a Tenacious and Persistence for variety in size. Other benefits of these inexpensive knives abound. If you needed to do other more abusive tasks or lend it to someone who you know won't be careful with it, who cares because it's a cheap knife and easily replaced.

In my opinion, there is a lot to be said for high value for your dollar knives like these when using them frequently and hard.

[Ankerson]

Based on the size it doesn't appear to be the steel itself fracturing as much as the edge just coming apart, this is likely simply due to the high volume of carbides and basically all you are seeing is the result of aggregates. In these PM steels the primary carbides are only a few microns in size but when they cluster in an aggregate this can be more than 10 microns easily. If the edge intersects one of these large aggregates then it is very likely going to end up as a weak point which will get rough as the carbide pops out of the edge. This is made even more dramatic if you hone to a very high polish and level of alignment (i.e. sharpness) and have a very low angle.

These steels in general are not really meant to keep this kind of edge - extremely fine and smooth cutting, they are made to cut that type of material well (cardboard) but generally do so at a low to moderate level of sharpness which they can keep on that material for a very long time. I would ask the question as to is this really the steel that will give you the performance you are looking for and I would think that AEB-L, or maybe even 19C27 would be more suitable. These will of course not have that long lasting edge retention with that rougher edge as they don't have the carbide volume to give the high wear resistance. But the edge composition is much more stable so they won't develop aggregate spots.

I do find the notion not to use the knife a bit odd, what else is it made to do. The only thing I would recommend is trying to stagger the cut contact point to make the wear a bit more even if possible. Note in regarding the angle, you only need to increase it

-wear you use it most (the base)
-just about half the depth of the chips (so it is a micro-bevel)

If you micro-bevel at 25-30 dps, but keep the micro-bevel very light as in just a few passes per side it will likely stop the aggregate wear and I doubt you could notice a significant loss in cutting ability as the bevel would be so narrow. You just need to make sure to work the primary angle to keep the micro from thickening.

True, they work better with coarser edges and will hold a certain level of sharpness for a VERY long time.

Once that sharpness curve levels out it will stay there at that level and just keep on cutting.

[Diamondback]

This discussion reminds me why I like VG-10 so much. Reduced cost, relatively good edge retention, easy to re-sharpen....less time spent in my personal "obsessive zone."

[Evil D]

This discussion reminds me why I like VG-10 so much. Reduced cost, relatively good edge retention, easy to re-sharpen....less time spent in my personal "obsessive zone."

I really like VG10 but the edge retention just isn't near as good for what i use it for. Difficulty of sharpening really is irrelevant to me, i have no problem at all sharpening 20CP so that argument doesn't mean much to me. I have a Centofante 4 which i do use occasionally and i love that knife a lot. For what i use a knife for i've found that S30V is really the lowest option, although calling VG10 a low option is cutting it a little short. If i found myself cutting less cardboard, i wouldn't hesitate to EDC VG10.

[Diamondback]

I really like VG10 but the edge retention just isn't near as good for what i use it for. Difficulty of sharpening really is irrelevant to me, i have no problem at all sharpening 20CP so that argument doesn't mean much to me. I have a Centofante 4 which i do use occasionally and i love that knife a lot. For what i use a knife for i've found that S30V is really the lowest option, although calling VG10 a low option is cutting it a little short. If i found myself cutting less cardboard, i wouldn't hesitate to EDC VG10.

...that makes sense that in a high-use environment you would want a Superior steel. I'm an old fart and mainly use my pocket carry for cutting string and opening packages. I will say however, I use a VG-10 Rescue and plain edge Endura in the garden that have seen "holy hell". No question they get abused; while at the end of several, long, rough days they may need a touch up, both those knives keep performing like champs. I would not want any other blade steel for day long work in my rather sizable back-yard garden.

[MachSchnell]

I would consider extensive cardboard cutting borderline abusive, but I do it from time to time. It's just such an abrasive material with so many impurities: rocks, glass, and dirt etc.

Why not use a trusty utility knife? And not one of the folding variety, they're just lousy in most cases.
You can replace a box cutter blade, but you cant replace a folding knife blade.

Side note: I've cut my fair share of cardboard and I notice that the blade can get quite hot-to the point where its hot to the touch... I wonder if there is any possibility of damaging the heat treat and temper from the constant heat from friction.

[Drkknight614]

I cut up some boxes after christmas with my Military. Started off razor sharp. I was only cutting for about half and hour but I could tell it was getting duller because it was becomin increasingly difficult to cut. A non dlc blade would probably work better too, but after I was done it wasnt shaving sharp anymore. It would cut paper but not smooth. So I stropped it, didnt take long at all and it was back to shaving sharp. With some of these exoctic steels, I would first see if many of the impurities found after extensive cutting can be taken out with stropping, before I ever took it do stones and such. You could always go to them later if it doesn't work. But this way, your not always removing tons of metal. It may just need a touch up on the strop after use.

[Cliff Stamp]

I wonder if there is any possibility of damaging the heat treat and temper from the constant heat from friction.

No, your skin will burn as low as 110 F, at which point you will feel pain and the cells start to die, extended exposure will generate a burn. The lowest tempering temperature used for steels is around 325 F, and most will temper much higher usually in the range of 400-600 F. The cardstock itself will ignite once it passes 450 F.

Of course the rate of wear is accelerated as the speed is increased, it would also be expected to be quadratic in speed so if you cut three times as fast you would expect almost ten times as much wear. It is usually a little worse than this because normally you lose control when you cut faster so for most people the rate is closer to cubic in speed.

Still even if you sharpened it every day to remove chipping on that level you are removing maybe ten microns or so worth of steel, that means it would take about a year to remove a mm of metal from the edge. Even if you were to do this every day, year in and year out, it would take about five years to thicken the edge to the point you would need to regrind the primary which would cost about $25 if you can't do it yourself.

If you look at the cost of the blade it is actually much less than constantly buying replacement utility blades unless you are going to use them with greater edge wear / damage.

My brother used to use standard OLFA knives and such (carpentry) he switched to high end folders years ago. Yes he does wear them out occasionally and I regrind the primary, but he usually just loses them first. Even in this case though a $200 knife which lasted 2-4 years has a cost of less than $0.25 a day, that won't even keep you in replacement blades for the utility knife.

[paladin]

+1 with jackknife
Also consider this Evil...cutting corr. cardboard seems to be a fairly pedestrian cutting chore at first blush, but feel your blade after zipping thru just one box...it gets quite hot. Also, as you well know, carboard is often a stew of recycled materials with A LOT of grit and abrasive chunks. Before I knew better, I ruined the temper of a Case slipjoint by cutting packing materials off of a couple of dozen new mattresses consecutively...I randomly looked down at my blade and imagine my astonishment to SEEING it had turned BLUE HOT I agree 110% that Spydercos are built for PRACTICAL cutting chores...but I submit my opinion that cutting cardboard every long workshift is a SPECIALIZED task requiring a SPECIALIZED tool, i.e. a razorknife, a.k.a. the humble boxcutter. I'm reminded of the warning never to use your knife as a prybar or a screwdriver...I propose that cutting cardboard full time would be a similar ( but less obvious ) misapplication of a tool.

[paladin]

several members shot me out of the saddle before I could pull the trigger on my post...I guess my 20 word/hr. typing skills are inadequate when a hot topic is posted. It should have been an omen when I had to login TWICE while typing my response. Oh well, even Matt Dillon sometimes got plugged.

[wvguy8258]

Yeah, I'd just use a cheap utility knife with replaceable blades for the cardboard.

I know, driving the Lamborghini is awesome, but if the lumber doesn't fit, it might be time to switch to a pickup truck.

Perfect analogy at the end. We don't use all our knives for the same cutting tasks, or a pocket knife for all cutting tasks.

[Diamondback]

several members shot me out of the saddle before I could pull the trigger on my post...I guess my 20 word/hr. typing skills are inadequate when a hot topic is posted. It should have been an omen when I had to login TWICE while typing my response. Oh well, even Matt Dillon sometimes got plugged.

...yes, but he had Doc and Miss Kitty to tend to his wounds.

back on topic....my son-in-law manages a grocery chain, and I know he and the stock boys, who cut a mountain of cardboard everyday, exclusively use box cutters. Containers of fresh replacement razor blades lie handy just about everywhere you look.....in the warehouse, beside the bailer, and even on a shelf below some of the registers. The old adage still holds true: "use the right tool for the job."

Years ago I owned a good size seasonal fruit and vegetable stand that ran from April-Thanksgiving. Much of the produce arrived in cardboard with the exception of the summer field-run fruit that would come in wooden bins. Only when I mis-laid my box cutter would I reach for the GIN-1 Endura I carried in my pocket. Even occasional use on those thick, cardboard, avocado boxes would tend to challenge the Endura's blade very quickly. My experience has taught me that when you're working hard, and trying to get a lot accomplished, an efficient tool makes for up for any style it may lack.

[razorsharp]

Just yesterday, I handled a Spyderco Persistence for the first time. I was really impressed with the quality of this knife for what it cost.

My suggestion would be to buy a couple of these value folders and take them both to work. When one gets dull through the day, just pull out the other one. If that Chinese steel is similar to AUS 8 then it might last half a day and it likely won't chip. You could touch them both up very fast at the end of your day.

Maybe mix it up and get a Tenacious and Persistence for variety in size. Other benefits of these inexpensive knives abound. If you needed to do other more abusive tasks or lend it to someone who you know won't be careful with it, who cares because it's a cheap knife and easily replaced.

In my opinion, there is a lot to be said for high value for your dollar knives like these when using them frequently and hard.

I dont know if its just me but that doesn't give me the tingly feeling inside like using a sprintrun does .... evil ...stick with microbevels at 20-22 a side .....I get glints like that on almost all my carbide steels, they are gone after after 1-3 touchups of the microlevel. For some reason I haven't noticed glints on my m390...the stuffs magic, I swear