How Do You Define Sharp?

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Krissig12

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Sep 11, 2013
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So you always hear people comparing steels on the basis of edge retention. But my question is what exactly do you guys consider to still be acceptably sharp? I'm always a little let down when I go through a box or two and my m390 or s110v is already unable to shave, even though I know that it will keep cutting boxes forever.

This is often referred to as a "working edge". But IMO a knife isn't SHARP unless it can shave. So how can I claim that any steels have exceptional edge retention when they all fail to hold the edge I want them to, and I never use them past the stage at which they still meet my standards?

It feels like I'm not really getting the full benefit of the better steels because I don't usually use them past the shaving sharp stage. Almost any cutlery steel could go through its whole life just cutting a box or two and getting touched up back to the same sharpness......so is there any real point in me dropping more cash on super steels? Other than to make me feel good, of course:rolleyes:

I know the simple answer is for me to just use them more before sharpening.... But like I said, it just irks me to have a less-than-shaving edge in my pocket......

Thoughts?
 
I am just like you, I'm ocd about my knives being razor sharp. I have learned one thing though, it all depends how much you use them. I was used to carrying lower end steels when I began my sharpness craze, my edc knife was always hair splitting sharp and if it wasn't I was in search of a makeshift strop to bring it back. But over time I learned that a knife that sharp has no practical use then showing off. That being said, the working edge comes into play. I carry a 154cm minigrip and it's an amazing knife. It'll hold a shaving edge through every every day task I use. Once I really start having to do some work with it I will lose the shaving edge but it'll still hold an amazing edge and cut all day long. Going back to scary sharp edges, one of the best uses of a screaming edge is skinning and gutting an animal. The sharper the better but I've still done it with a knife not any sharper then a dollar store steak knife. So basically it all comes down to how much you want to show off. The working edge is all that really matters and a better steel will hold a shaving edge longer.

P.s. just a tip, with the higher end steels get them as sharp as you can. Spend the time and take real good care when sharpening to get the sharpest edge possible. I found that the sharper a good steel is, the longer it takes to lose the shaving edge. Good luck!
 
I sharpen a lot of knives for friends and other connections with a Wicked Edge sharpener and I usually sharpen until shaving sharp or slicing paper as well as any dangerous paper should be cut, but the one thing I have seen repeatedly is that a shaving edge only lasts until repeated tasks like cutting cardboard as you said or whittling wood a favorite of mine. Once you repeatedly cut the razor edge is gone and you have a working edge or utility edge which is where most peoples knives seem to live and I have seen this with every common steel ( 154cm, D2, S30V, M390, S90V, S110, ZDP189, and more). The angle plays a big part, a better slicing angle 12-15 degrees per side cuts like a razor but will dull quicker than a 20-24 degree edge per side which will last a little longer but just won't feel as scary sharp. I think if your one of us who can't stand a dull knife you may want to find which ever sharpening system you can operate efficiently so you can touch up your blades routinely since it sounds like you are working those blades as they should be. One last thing as you said was 1-2 boxes and the s110v was dull, the working difference between most of these steels is very minimal if you do a side by side, thats why so many custom knife makers still use D2 or 154cm.
 
If the blade will slice through a cigarette paper, it's sharp.
 
I've also wondered what peoples definition of sharp was kind of like there are a lot of different definitions of blade play. Bottom line, if it's not shaving sharp I'll grab one that is for the day. I've never been one for super steels. I like to touch up my blades often and am perfectly content carrying some good ol' 1095. However, I don't really consider 154 or s30v super, because they're pretty much a standard in the price range I stick to.
 
My definition of sharpness arranged in a tiered structure. 1 being the sharpest and decreasing from there.

1: Treetops arm hair like nobodies business.

2: Push cuts phone book paper with no snags.

3: Slices phone book paper but will not push cut.

4: Push cuts printer paper with no snags.

5: Slices printer paper but will not push cut.

6: DULL AS F**K

You may have noticed that as soon as it cannot slice printer paper it is defined as dull. I usually sharpen my new knives to #1 and then once they reach phase 3-4 I'll strop them back to a 1-2. I'm probably over thinking things, but that's how I define sharp.
 
If you can shave with an ax, its been sharpened in incorrectly. If you can split wood with a scalpel it been sharpened incorrectly.
 
I normally define how sharp by what sort of finish I apply, whether coarse, medium, or fine - and that depends on the job its intended to do and the steel it is made from.

If the edge cuts well at whatever finish level and feels three finger sticky, I'm happy. The higher carbide steels will tend to keep that nice draw cutting performance for a long time. Getting them to cut well refined will require working them on some fine diamond media, and even then (in my experience), some of the lower carbide fine grained steels will last just as long when worked to a fine edge. That said, most steels should cut a bunch of cardboard and still be shaving sharp. Some will depend on the cardboard and the angle you cut through it at - go through at an angle and it will part more easily, also allow some wedging action. Cutting straight down through double or triple wall can dull an edge very quickly.

Ultimately an edge is a consumable tool, and will need to be touched up as the demands of the job and random contact dictate. A big part of getting the most from them is to customize your maintenance scheme. At times it makes more sense to work on creating a better coarse edge and running that for a much longer time frame, than shooting for an edge finish that is a poor fit for the work being done.
 
I don't have the need to cut much cardboard, and when I do I use a utility knife.

For me, if a knife easily cuts phone book paper or thermal receipt paper - it's plenty sharp. And if sharpened well, will stay that way for a long time.
 
When it can shave smoothly it's sharp enough. As others have said, that kind of edge doesn't really last that long but I find it to be a good benchmark. Treetopping sharp can be a fun exercise on a rainy day, but those edges last even less. IMO it's not worth the trouble 99% of the time. Most of my edc cutting doesn't require scalpel sharpness.
 
personally im a working edge type of guy my chopping style knives are no where near as sharp as my slicing knives...
 
Krissig12 said:
So you always hear people comparing steels on the basis of edge retention. But my question is what exactly do you guys consider to still be acceptably sharp? I'm always a little let down when I go through a box or two and my m390 or s110v is already unable to shave, even though I know that it will keep cutting boxes forever.

This is often referred to as a "working edge". But IMO a knife isn't SHARP unless it can shave. So how can I claim that any steels have exceptional edge retention when they all fail to hold the edge I want them to, and I never use them past the stage at which they still meet my standards?

It feels like I'm not really getting the full benefit of the better steels because I don't usually use them past the shaving sharp stage. Almost any cutlery steel could go through its whole life just cutting a box or two and getting touched up back to the same sharpness......so is there any real point in me dropping more cash on super steels? Other than to make me feel good, of course:rolleyes:

I know the simple answer is for me to just use them more before sharpening.... But like I said, it just irks me to have a less-than-shaving edge in my pocket......

Thoughts?
Click to expand...
There is a fair amount going on in this one post. I tend to sharpen my knives whenever they stop easily shaving. As for sharpening and when is it sharp enough, I sharpen until it treetops arm hair or head hair for pocket knives and work knives, unless they are intended for rough work like root cutting or such. Even when sharpening for chopping, I put a very sharp edge on, as it easily shaves my arm. My wife's favorite kitchen knife gets sharpened until is will easily shave my arm or maybe treetop head hair. Each user can sharpen as much or as little as they want. Most people (nonknife people) don't get impressed until it can shave their arm. For improved edge holding of the type you are after, if sharpening doesn't work, try higher hardness steels with more moderate wear resistance. I found a sweet spot with M2 high speed steel at 65 Rockwell hardness. It's really impressive when you can still tree top arm hair after 30' of cardboard.

If you're only getting through a box or 2 before loosing that shaving edge, you may want to examine your sharpening procedure. I just finished cutting a box into 1/2" wide strips and the knife still shaves my arm. Obviously not as easily, but it still does. Cardboard varies widely, but sharpening is where I'd start.

I decided that super steels don't really benefit me, since I sharpen my knives fairly frequently, and can cut wood in the back yard all afternoon with a $10 machete and it will still shave my arm. Again, not as easily as when I started, but it will do it.

Just a tip, thinner angles will hold an edge longer than thicker ones, as long as they are not too thin and just crumble/buckle when used. For instance, edges used for meat cutting can handle disturbingly low angles, while cutting wood requires a higher angle. The point is, lowering the angle as much as possible while avoiding crumbling will get the most edge retention. If you are willing to have specialized knives, you can get ridiculous edge holding from even fairly mundane steels. For general purpose stuff, you'll have to do some experiments for the roughest use the edge gets.
 
Two straight and smoth surfaces who meets in a low angle = sharp.

straight - is a perfectly straight cutting edge seen from above.

Smoth - is about how fine sharpener you ends your sharpening process with.

Meets - is about your skills and knowhow.

Low angle- is about to what you shall use your knife.

Thomas
 
This is some kind of mystery to me. I sent a knife off to be sharpened because i had it shaving my arm hair but it wouldnt even bite computer paper. I couldnt decide if it was sharp or not. Does anyone have an opion on "sharp" when it will pass one test but not another
 
As HeavyHanded mentioned, three finger sticky is a great test. It can be 400 grit toothy sharp, or 0.5 micron HHT sharp. Both will bite into your fingers quickly. Both are sharp.
 
HeavyHanded said:
I normally define how sharp by what sort of finish I apply, whether coarse, medium, or fine - and that depends on the job its intended to do and the steel it is made from.
Click to expand...

I think Martin nailed it. If I use a kitchen knife for instance, I do not care at all whether it cuts or push cuts phonebook paper or whether it shaves or tree tops hair. I care whether it cuts tomatoes the way I want it, or a mushroom or a vanilla bean - you get the idea. I like to maintain that very tool to be good at its purpose, even if it means regular daily or hourly touchups. Yes, if there is a steel that holds that type of edge I want longer and at the same time makes a touch up still reasonably easy when needed, that is an advantage.
 
jtho8774 said:
This is some kind of mystery to me. I sent a knife off to be sharpened because i had it shaving my arm hair but it wouldnt even bite computer paper. I couldnt decide if it was sharp or not. Does anyone have an opion on "sharp" when it will pass one test but not another
Click to expand...

That was a 'sharp' and thin burr; classic burr behavior. The thin burr will shave easily, as you noticed, but it quickly folds over on the somewhat 'tougher' paper. When the burr is completely gone, and the underlying apex is clean and crisp, it should pass both tests easily and repeatedly; should be able to go back & forth between paper-slicing and shaving, if the edge is crisply apexed and burr-free, assuming the steel's heat treat is decent enough.

I'm with Martin (HeavyHanded) on the definition of 'sharp'. If the edge easily does the job for which the steel and the blade were designed, it's sharp. Most 'knives' were not designed or intended for shaving; so, expecting shaving-sharpness from them at all times is an exercise in frustration. It's always nice to see that it can shave immediately off the hones & strops (good gauge of a job well done), but it's usually unrealistic to expect even a lot of 'super steels' (whatever that means) to retain much shaving sharpness after some hard, or even moderate, use. Shaving is more about thin geometry and sufficient hardness (heat treat) to support it; don't need a super alloy or uber-hard carbides to make that happen. The best true 'shaving edge' I have on any of my EDC knives is in good ol' 1095.


David
 
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jtho8774 said:
This is some kind of mystery to me. I sent a knife off to be sharpened because i had it shaving my arm hair but it wouldnt even bite computer paper. I couldnt decide if it was sharp or not. Does anyone have an opion on "sharp" when it will pass one test but not another
Click to expand...


Sounds like you have a rounded edge apex. How do you achieve the shaving edge?
 
Well, I'm OCD as well as some of you on this post. After I use my knife, I'm test cutting printer and/or phone book paper on it, and then I'm looking at it under a flashlight to see if I can see any shiny metal on the edge that shouldn't be there aka dull spots. If there is, then out comes my Sharpmaker for a touch-up. I don't need it to shave hair though, just smoothly cut through paper, and pass my visual inspection of dull spots.
 
My EDC is shaving sharp because that is the way I like it.
My work knives are sharpened to do the jobs they need to do but are not shaving sharp. They do hold an edge and slices paper cleanly which is what I need.
My "work in the yard" knives are also "get the job done" sharp...they won't cleanly slice paper but they will slice through plants, etc. If I have to plunge them into the ground and cut roots, etc. they do the job nicely.
Those levels are all that I need and prefer.
 
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