Scary sharp blade really worth it?

[Ben Dover]

So I would think that the sharper it is the longer it would take to get dull again. Or am I just confused??

In my experience you are correct. The more refined the edge, the longer it will do the job.

Sure, a scary sharp edge cutting cardboard all day won't be scary sharp anymore, but it will still be cutting the cardboard long after the so-called "working edge" won't cut anymore.

 

[nozh2002]

Scary sharp does not last.

This is very strange statement, really. I can understand that "scary sharp" edge will eventually dull to the same state as under-sharpened edge and it may be take not too long to became as dull as unersharpened-edge. But to say that under-sharpened edge will keep it's dullness longer then "scary sharp" - this is beyond my understanding.

I think scary sharp edge will last as long as under-sharpened, plus the time it take it to came to same dullness as under-sharpened. Simple math:

T1 - time for "scary sharp" to became as dull as under-sharpened
T2 - time for under-sharpened edge to became dull
T1+T2 - total time for "scary sharp" to became dull

Thanks, Vassili.

 

[me2]

The way I see it, the working edge is what you have after the scary sharp edge is gone. I had just sharpened my $10 folder, then used it to cut cardboard to take to the recycler. It was still sharp afterward, but the hair shaving ability was all but gone; hair scraping was about what was left. That is what I call a working edge. Essentially, once you hit a working edge, it will last and last, because its already blunt.

However, a polished edge will last for a while; even my cheap Kershaw Vapor 2 would still shave hair off my arm after over 500 cuts into cardboard, each ~1" long, in the same 1/2" or so of blade length. My Old Timer took 128 cuts along the full length of its 2" blade into aluminum cans, cutting from top to bottom through the sides, and would still shave. Both these were done with starting edges that would whittle beard hair after honing on my 1x30 leather belt on the Harbor Freight sander. While neither would still do that, they would both easily shave hair from my arm when the cutting was done.

 

[db]

WOW!! Could we argue with any more general terms? I’d say my super duper sharp edge doesn’t last nor does it work as well as my wang dang doodle sharp edge does. Now that is a fact.

 

[1Bigdog]

IMHO with all other factors being the same, the sharpest edge is one that has the least thickness at the edge.

The thinner the edge, the weaker the edge, the quicker the edge will roll to the side and equate to being dull.

The thicker the edge, the greater the angle, the stronger the edge is = the longer the knife retains its original sharpness.

 

[nozh2002]

IMHO with all other factors being the same, the sharpest edge is one that has the least thickness at the edge.

The thinner the edge, the weaker the edge, the quicker the edge will roll to the side and equate to being dull.

The thicker the edge, the greater the angle, the stronger the edge is = the longer the knife retains its original sharpness.

I think you are talking about edge angle.

Angle on the edge has nothing to do with ability to whittle hair. My edges are all 30 degree. Thickness of the edge has nothing to do with angle - this is how wide edge shoulders are - and this is has nothing to do with ability to whittle hair too.

Thanks, Vassili.

 

[realitycheck]

The way I see it, the working edge is what you have after the scary sharp edge is gone. I had just sharpened my $10 folder, then used it to cut cardboard to take to the recycler. It was still sharp afterward, but the hair shaving ability was all but gone; hair scraping was about what was left. That is what I call a working edge. Essentially, once you hit a working edge, it will last and last, because its already blunt.

However, a polished edge will last for a while; even my cheap Kershaw Vapor 2 would still shave hair off my arm after over 500 cuts into cardboard, each ~1" long, in the same 1/2" or so of blade length. My Old Timer took 128 cuts along the full length of its 2" blade into aluminum cans, cutting from top to bottom through the sides, and would still shave. Both these were done with starting edges that would whittle beard hair after honing on my 1x30 leather belt on the Harbor Freight sander. While neither would still do that, they would both easily shave hair from my arm when the cutting was done.

me2 You actually purposefully tested your knife this way??

 

[gunmike1]

If your definition of working edge is the hair scraping remnants of a polished edge, then yes, that "working edge" won't last. If your definition of a working edge is closer to mine, something akin to a Tom Krein 120 grit edge that tree tops hair, then I think you will see tremendous edge retention doing extended slicing, especially with steels like D2, S30V, and ZDP 189. I have yet to put an edge on a previously Krein sharpened knife that will slice for as long as his edges do. Sure, I can get them to whittle hair, but his edges just slice and slice. For me a tree topping edge from a Spyderco medium stone that cuts free hanging hair works well for most EDC needs and I would think of as a good working edge, though I would probably go DMT Coarse, which I can get to shave very smoothly and sometimes pop some hairs on some of my knives with better steels, for pure cardboard slicing. Being afflicted with sharpening OCD usually makes me sharpen out to at least 1 micron finishes, and sometimes even .05 micron finishes (anything worth doing is worth doing obsessive compulsively!). I generally put those edges on some of my knives that are extremely thin and acute (actually, that would be most of them), where the cutting ability is so high that that the knife just pushes right through the material as you cut it. To each his own though, as there are so many factors from what you are cutting, how you are cutting it, the steel/heat treat, geometry, ect., that make your ideal edge for carry different than mine or most anyone else's. Add to that that most of my freinds consider my working edges scary sharp and we have even more confusion as to what the hell we are talking about.

Mike

 

[nozh2002]

If your definition of working edge is the hair scraping remnants of a polished edge, then yes, that "working edge" won't last. If your definition of a working edge is closer to mine, something akin to a Tom Krein 120 grit edge that tree tops hair, then I think you will see tremendous edge retention doing extended slicing, especially with steels like D2, S30V, and ZDP 189. I have yet to put an edge on a previously Krein sharpened knife that will slice for as long as his edges do. Sure, I can get them to whittle hair, but his edges just slice and slice. For me a tree topping edge from a Spyderco medium stone that cuts free hanging hair works well for most EDC needs and I would think of as a good working edge, though I would probably go DMT Coarse, which I can get to shave very smoothly and sometimes pop some hairs on some of my knives with better steels, for pure cardboard slicing. Being afflicted with sharpening OCD usually makes me sharpen out to at least 1 micron finishes, and sometimes even .05 micron finishes (anything worth doing is worth doing obsessive compulsively!). I generally put those edges on some of my knives that are extremely thin and acute (actually, that would be most of them), where the cutting ability is so high that that the knife just pushes right through the material as you cut it. To each his own though, as there are so many factors from what you are cutting, how you are cutting it, the steel/heat treat, geometry, ect., that make your ideal edge for carry different than mine or most anyone else's. Add to that that most of my freinds consider my working edges scary sharp and we have even more confusion as to what the hell we are talking about.

Mike

Well, this is fine with me, but someone start saying that working edge will last longer - this is simple inaccurate statement, simple because all terms in it not defined.

There are four major parameters IMHO of sharpened-
I Angle - angle between edge sides (let say angle at very edge because edge may has micro-bevel or be convex...)
II Thickness - width of blade shoulders, where edge sides (secondary bevel) meet the blade bevels
III Polish - size of last abrasive which was used on edge or size of micro tooth on the very edge.

So far proven that any sharpened edge will be able to shave or chop hanging hair, with any polish - fine or coarse. But only edge with very fine polish able to whittle hair.

Also proven that edge with coarse polish will slice rolled toilet paper better then edge with fine polish under small pressure applied.

Thanks, Vassili.

 

[sodak]

I think a lot of the problem is terminology. The sharper your edge, the longer it takes to dull. Generally. I also find that thin edges last longer, with the proper steel, than thick edges, because it takes less pressure to cut with.

A lot of variable here to lock down before reaching agreement.

 

[ss Dragonfly]

Hey Guys
Try the best of both worlds, tip polished and 2/3 blade a little coarse. Spyderco fine ceramic for the tip and DMT fine works for me. Works well for all occasions short of shaving your face. I don't do that anyway. Shane

 

[Ben Dover]

Terminology needs to be defined.

The people I know who say they want "a working edge, not a shaving edge" will usually use something like a corborundum or India stone, and sharpen until the edge feels "toothy." These edges will not shave armhair, but they will whittle green soft wood, or slice a tomato. They need resharpening after virtually every use.

That was why I made the comment about them lacking the patience, or skill, to sharpen properly. If a knife will shave, it's fairly sharp.

I prefer the refined edge because it seems to me that the carbides don't break out of the matrix quite as easily, and unless you're abusing the edge, even the lesser steels will hold the edge fairly well.

The only "test" that I've done, if you can even call it a test: When I first acquired the belt sander, I dug through my box of old "beater" knives and got out a couple of folders made from 420 steel. I knew from experience that these wouldn't hold an edge worth a damn, but I wasn't really interested in that, I was trying to learn how to use the belt sander. I convexed and highly polished these blades.

I took them out with me on a camping trip, and used them to whittle dry scrub oak. Now dry wood will dull just about any blade eventually.

To make a long story short, these "el cheapo" knives did dull, but it took about three times as long to dull them as it had in the past when they were sharpened only to the point of shaving arm hair with crock sticks.

I realize this wasn't a very scientific experiment, but it convinced me that highly refined and polished convex edges were superior for my personal useage.

 

[me2]

me2 You actually purposefully tested your knife this way??

Yep. I have a Mountain Dew habit, and had about 12 empty cans lying around, so I started cutting vertical slits into the side with the Old Timer. We also had plenty of cardboard left over after Christmas, so I used that too. I ran out of cans, so that test ended. For whatever reason, I dont think I've tested the cardboard cutting ability of the Old Timer.

GunMike, your definition of working edge and mine are not the same, so we wont be able to compare them. I definately agree w/ you that a coarse "working edge" will out last a polished edge for different types of cutting, and some steels work better than others for this. However, as pointed out many times by several people, including He Who Shall Not Be Named, you, and Tom Krein, coarse edges dont prevent scary sharp edges, so that is not the definition I use. I have tried to duplicate what Krein can do with a belt, but havent been able to get that level of sharpness yet, although my 1095 kiridashi shaves arm hair easily with no stropping straight from a 220 or 320 grit belt. The coarser grit attempts were using some gas station stainless, and while it would cut, it was not as sharp as my normal using edge. For a long while, I used my TSEK with the final edge applied on the Norton Fine India stone. This would shave and whittle beard hair, but was still coarse enough to saw through paper and cardboard.

 

[dantzk8]

I think scary sharp edge will last as long as under-sharpened, plus the time it take it to came to same dullness as under-sharpened. Simple math:

T1 - time for "scary sharp" to became as dull as under-sharpened
T2 - time for under-sharpened edge to became dull
T1+T2 - total time for "scary sharp" to became dull

Thanks, Vassili.

So far proven that any sharpened edge will be able to shave or chop hanging hair, with any polish - fine or coarse. But only edge with very fine polish able to whittle hair.

Also proven that edge with coarse polish will slice rolled toilet paper better then edge with fine polish under small pressure applied.

Vassili,

Since this thread is opened i've tried different finishes on a 1075 carbon steel and on a zdp189 one and tested those edges on hair, paper roll and cardboard . I've been the most rigorous i could in my experiments about cutting abilities and edge durability. Your above statements are right for me.

dantzk.

 

[StretchNM]

I think individual perspective might be the key here. If a guy's aim is to end up with a dull knife, he's better off NOT starting with an ultra-sharp edge. If he starts with the sharpest edge possible, he has more work to do to end up with a dull knife.

My problem is to sharpen my knives as insanely sharp as I can get them. Dulling them is easy - I have no problem there. Just use them.

If you for some reason want a dull knife, then start with a dull one. If you want a sharp knife to work with, get it as sharp as you can.

 

[Ben Dover]

I think individual perspective might be the key here. If a guy's aim is to end up with a dull knife, he's better off NOT starting with an ultra-sharp edge. If he starts with the sharpest edge possible, he has more work to do to end up with a dull knife.

My problem is to sharpen my knives as insanely sharp as I can get them. Dulling them is easy - I have no problem there. Just use them.

If you for some reason want a dull knife, then start with a dull one. If you want a sharp knife to work with, get it as sharp as you can.

And that post, sir, encompasses more common sense than entire remainder of this thread! Thank you for poting it!

Ben

 

[nozh2002]

I sharpen another knife - ZT302 with coarse polish. I use only DMT D11C - Coarse with 325 grid. I raise burr on both sides and then remove it not really raising angle but just with patience changing sides, no pressure. In result I guess it has 45 microns tooth on the edge - Swamp Rat has 9 microns tooth after Extra Fine and Microtech SOCO has 0.15 microns tooth on the edge.

In result this 45 micron tooth cut through same twisted piece of toilet paper I used in my video - full width, just cut it in two pieces. For sure it sews better.

It also shave my arm - difference is that I think in this case it does not really cut hairs but instead catches them between tooth and tear up. It is a bit painful, it defenetely trying to pull hair out before cut it and in result of this tension hairs popping out.

No way to whittle hair or cut it.

I think 325 grit is bit extreme for edge, I can not imagine how useful 120 grit edge will be - however belt grinder may has different abrasive effect, because of speed.

I will try to see what difference is between 0.15, 9 and 45 grit edges.

Thanks, Vassili.

 

[gunmike1]

Good to see your results, Vasilli. The coarse edges definately slice aggressively. I think we should think of sharpness in 2 ways (I believe Cliff Stamp has said this before): Slicing sharpness and Push cutting sharpness. I got the Spyderco Mule team knife to cut free hanging hair and shave above the skin with the 325 grit DMT finish when I used the DMT Coarse stone to put a 12 per side microbevel on a 9-10 per side main bevel. I then went to 600 grit and it was tree topping arm hair easily. I would guess that 325 grit finish would slice for a very long time, considering how well it was pushcutting at that finish with nice teeth in it. Since it was a microbevel it only took a few passes per side and never formed a burr that could be seen by my lighted microscope. I had cut straight into a Spyderco medium stone prior to sharpening the microbevel to remove any weakened steel from the rebevelling. This knife gets very sharp, at least as sharp as my M4 Ultimate Caper, which really impressed me when sharpening. It will be interesting to test it out and see how sharp it gets when truly polished and compare it to other steels.

Mike

 

[nozh2002]

It is not clear. The fact that it slice better without any pressure applied does not mean that it will slice better when there is some pressure. Because in this case it will be push+draw. Slicing without any pressure applied is not real world example. IMHO there are more push cut in what mostly knives are used for.

The problem is that I a not sure how to test this. My thread cutting sharpness test I guess will not show coarse grid sharpness. Also I guess different materials may be better cut by draw and certain by push cut. It kind of complicates thing.

I can also imagine that different steel may hold tooth better then other while other may hold angle without tooth better.

So far too many variables...

At least can we all use same terms - edge angle, edge thickness and edge polish?

In this terms working edge - is like coarse polished edge I guess.

Thanks, Vassili.

 

[hardheart]

I dunno, working edge in many instances seems to mean 'haven't gotten it to shave yet'

coarse polished, I guess that's like military intelligence (I'm in MI )