How sharp is sharp?

I'm of the opinion you should use the same test every time.

I personally use cheaperthandirt catalog paper, there's a new one every month so I never seem to run out. I do two tests the first being cutting the paper on the edge. The second test I roll or gently fold the paper and try to cut into the roll then come out of it making an oval section.

For me I'm happy if it can cut an oval out of the rolled or folded paper. Alternatively if it can easily/cleaning slice through the unfolded paper by just swiping the knife at the paper I say it's sharp. It's probably not toilet paper cutting sharp or hair whittling but I'm happy with it.
 
Skimo said:
Yeah, you pretty much nailed it, there's a reason no one uses tactical kitchen knives and a reason so many people compliment Opinels on their slicing. I do have to add for clarity that an axe can be sharp enough to remove hair cleanly and still have the right geometry.
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I agree with that, but it wont split dry ash for long without the edge being blunted. Better do the shaving first. :)
bpeezer said:
I have no doubt that you understand cutting things, the only reason I said anything is because the OP specifically said besides "does it cut what you need it to cut?" That being said, there is nothing wrong with taking a blade to a higher level of sharpness than necessary for ligutht use tasks. I take every one of my EDC blades to hair whittling sharp. They definitely don't need to be that sharp, but their performance doesn't suffer from being taken there.

Like most here, I think that a simple paper test will tell you a lot about an edge. The same paper can be used for different levels of sharpness, based on sound (as others have mentioned). And if the knife struggles to cut paper at all, I believe it's not sharp enough regardless of intended use.
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I think your reasoning is sound, testing an edge to find what degree of sharp has been attained is a good practice. I live on 60 acres and carry two blades during the day. One is a two blade Case pocket knife which I keep at shaving sharp, I use it for purposes that will not make the edge deteriorate with use. If I have a job that is to challenging for the folder, I pull out me 1084 straight knife that carries an edge that does not shave as easily, but holds up better when used on the more aggressive task. I'm selecting the right edge for the job. If I'm in the woods, I also carry a small hand ax, which will not shave hair but will split wood all day long. No single edge will do all jobs, putting to fine an edge on a hard work knife I don't believe is very practical. If I were a chef and worked in the kitchen all day my selection would be much different.
 
It's sharp enough when I run out of bandaids. ;)

If it shaves arm hair and cleanly slices paper (no push or pull) then I'm happy.
 
Just being able to cut what I need to cut is dull for me. I like my knives sharper than they NEED to be.
 
Story Time:

A sharp knife is one that you can accidentally cut yourself with and not know. I got in a Buck Metro years ago and it was very sharp, but it being a Buck Metro I thought it was puny and insignificant and didn't take it as seriously as I should of. But I still tried to handle it with care as it was still a knife.

Since it was brand new and just out of the box I do what I do with all my one hand openers, I open and close it repeatedly with one hand till it feels natural. While I was doing this I was on the computer as well as this doesn't require much attention to do or so I thought. But I eventually look back at the knife and I see something funny on the top of my desk, it looked soft and almost gel like and felt like skin so after examing it for a good minute or 2 in the hand I wasn't opening and closing my knife with I decided it felt too much like skin to be a coincidence.

So I looked at my right thumb and saw a very large chunk of it missing, about half the size of your pinky nail. The strange part there wasn't a single drop of blood, not even a spec of anything remotely resembling it. So what did I do. I poked it! Not once but multiple times. Why, because I thought it was strange there was no blood. Than I saw a drop of blood, so I poked it again. Than a whole lot of blood followed that, so I wrapped it up as I don't think a band aid was going to work all that well in that situation. 40min latter, still bleeding.

I learned 2 valuable lessons that day. First that dang Buck had one mean edge to it dispite it being a puny blade which is useless in my opinion it's still freaking sharp and earned my respect in that regard. Second don't poke a very clean cut if it's not bleeding.


But I don't like the idea of inflicting injury upon myself to see if a knife is sharp. So I use cardboard to test out my blades to see if it's sharp. It's a real world test for me as it's what my knives do the vast majority of the time. So it's sharp when I say it's sharp.
 
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I'll steal a quote (again) from Murray Carter:
A knife is sharp if it is three finger sticky and can shave arm hair.
As for what is sharp enough all depends on the task. A whittling edge is great for shaving your face and some fine carving jobs, not a whole lot else, and not for very long. A tree-topping edge is a lot easier to get to and holds up a bit better. For rough work, a coarse edge that can barely nip arm hair might be the best choice.

I generally go by pressure, whatever edge finish allows me to make the cut with the least amount of pressure is probably going to last the longest. A coarse edge for chopping or carving is a bad choice to begin with and will get worse quickly, a fine edge for cutting rope or many synthetics is likewise not going to perform well initially and won't hold up well. Generally I find a moderate grit edge at a fairly acute angle will last longest over the widest range of materials. You have to experiment a bit, but given all the variables that statement by MC is a good baseline.

Martin
 
MC got caught up in sharpness debates a while back, you probably already know that though, cleanest apex at whatever grit is going to be sharpest and theoretically last longer until you start chipping and rolling. Every edge is going to be different depending on the steel, geometry, heat treatment and intended use. One of the reasons I think micro bevels may offer increased performance with a thinned out edge.
 
Skimo said:
MC got caught up in sharpness debates a while back, you probably already know that though, cleanest apex at whatever grit is going to be sharpest and theoretically last longer until you start chipping and rolling. Every edge is going to be different depending on the steel, geometry, heat treatment and intended use. One of the reasons I think micro bevels may offer increased performance with a thinned out edge.
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Yes and no IMHO. Once you start to designate fairly specific chores for a given cutting tool, the edge finish becomes an increasingly important factor (all other things being equal) in performance and longevity (again, all other factors being equal). Am slowly coming to the conclusion that pressure is the number one killer of the sharp edge, no matter what the task. This even encompasses cutting abrasive materials, as all that is happening is a concentration of pressure at the point of the abrasive contact. Is very difficult to get a definitive measure of "what is sharp", or "what is sharp enough". As you say, and I agree 100% - at pretty much any finish level, if the edge is clean it will be sharp - at least for some chores...
For a generic measure that can be applied to most cutlery, "3 finger sticky and shaves some arm hair" is about as good a measure as any.
 
I prefer feedback from my customers... offer free resharpens to those dissatisfied.. (have yet to give one away)
My customers are those that typically don't appreciate "sharp" as I do (housewives, weekend BBQ's). Therefore I have to take their safety into acct. And found I had to dumb my edges down after responses such as "F#@*%! sharp" and "damn it Phil".
My personal preference is "eyes bleed when gazed upon sharp" but take care when lending my steel or sharpening for the inexperienced.
I do use the weekend newspaper to test (as I find the intended use to be only disappointing, ie...reading it) there is a difference in edge if you can push cut as opposed to slicing thru.
 
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