standard test for sharpness?

nozh2002 said:
Chopping bottle and paper is fun, but it is proven that it has nothing to do with sharpness. I did same with knife with ruined edge. But it is fun to do, if you are careful.

Thanks, Vassili/
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I want to see a video of anyone cutting a piece of phone book paper with a "ruined" edge - this is not possible in my experience. This "trick" requires the entire blade to be sharp, and I have knives that will whittle hair yet cannot cut a rolled up tube of phone book paper. If you have difficulty moving your knife in a semi-circular fashion without stabbing yourself, I don't know what more to add, other than to say stay away from brush clearing and wood chopping! I can tell you it takes more work to get an edge to cut the paper than it does to get it to whittle a hair.
 
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And I'll agree that this level of sharpness will not survive for very long in many real world uses (I cut some carpet last night, and that sharpness was gone with the first cut), so for many it is a purely academic exercise. The stone was needed after cutting the carpet. I was at a higher risk of cutting myself cutting that carpet than I ever am cutting a tube of paper!
 
Broos said:
I want to see a video of anyone cutting a piece of phone book paper with a "ruined" edge - this is not possible in my experience. This "trick" requires the entire blade to be sharp, and I have knives that will whittle hair yet cannot cut a rolled up tube of phone book paper. If you have difficulty moving your knife in a semi-circular fashion without stabbing yourself, I don't know what more to add, other than to say stay away from brush clearing and wood chopping! I can tell you it takes more work to get an edge to cut the paper than it does to get it to whittle a hair.
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The cut involves a bit of technique, if you try hack at it with the edge parallel to the roll, then it sometimes will cut it, but if you chop at it with a tilted angle so that it slices the roll, then you have a higher chance of cutting through it, especially with longer blades. Whittling hair, or shaving requires no technique and there is a lower risk of a very bad cut.
 
Murray Carter three finger sticky sharp test... ;)

Used on both sides and along the full length of the edge.
 
Broos said:
And I'll agree that this level of sharpness will not survive for very long in many real world uses (I cut some carpet last night, and that sharpness was gone with the first cut), so for many it is a purely academic exercise. The stone was needed after cutting the carpet. I was at a higher risk of cutting myself cutting that carpet than I ever am cutting a tube of paper!
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A good point. What grit/finish edge in your opinion is best for your real world use? For me I've found someplace around a 2000 ish finish is what I like most. Btw a well done very coarse edge would have worked on that carpet pretty well. I've found carpet is a real edge killer.
 
db said:
A good point. What grit/finish edge in your opinion is best for your real world use? For me I've found someplace around a 2000 ish finish is what I like most. Btw a well done very coarse edge would have worked on that carpet pretty well. I've found carpet is a real edge killer.
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I could be happy with a 600 grit DMT edge (1 or 2 swipes on the strop) for most uses, and like the edge a shapton 1000 or 2000 leaves also. But most of my users have polished edges. In general I think the advantage of a coarse edge is usually one of control - they offer more control of the cut.

Roger999 said:
The cut involves a bit of technique, if you try hack at it with the edge parallel to the roll, then it sometimes will cut it, but if you chop at it with a tilted angle so that it slices the roll, then you have a higher chance of cutting through it, especially with longer blades. Whittling hair, or shaving requires no technique and there is a lower risk of a very bad cut.
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I think if you try this, you will find the same thing I did, that sharpness determines whether you can make the cut or not. All you have to do is take a casual swing and hit the paper - if it is sharp enough, it will cut it. If there is one little section with very minor edge issues, it will not cut it. Like sports, the best swing to cut with looks and feels natural & unaffected, and if you try to think about one thing you might even miss the paper tube. All you should think about is hitting the paper. Put the knife down when you are done (I'm kidding! :p I've made a couple knife related ER trips, too). There is not much slice action in a natural swing at a 1" deep target. And if you think that holding the knife at an awkward angle to try to increase slice is important, I've tried it, and it never helped me make a cut. A sharp knife swung naturally is the best way to do it, and if the knife is sharp enough, and the paper is not too moist, it will cut it. It's just one of my gauges for really sharp.

With the exception of Noz, who says he can do it with a "ruined" edge (uh huh :yawn:), I haven't got anyone to post anything other than why they don't, won't, or can't do it. Reading between the lines makes me think that some of those hair whittlin' knives can't make the cut. Or maybe not. Or maybe I'm just being difficult (runs in the family). Either way it is hard to gauge a sharpness test when you have not tried doing it or have not done it successfully.

The more different sharpness tests you do will give you better understanding of how to sharpen. Why limit yourself to one or two? Some tests, for example Carter's 3-finger test, gives you a feel for the steel that the others can't.
 
My test is to hold my hand limp with the palm facing upward and very lightly touch the edge to my finger nail. If I can feel it grab a hold with the slightest touch, then it's sharp That's my quick test. The test beyond that is to see if it'll split a hair.
 
The best test is to use your knife for its intended purpose. No point testing it on beancurd or diamond when its supposed to be a cleaver. If it can't cut what its meant to cut, then something is wrong somewhere.
 
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Sengseng said:
The best test is to use your knife for its intended purpose. If it can't cut what its meant to cut, then something is wrong somewhere.
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I don't know about that... After I sharpen my knife, I like it to be in "perfect" condition. If I test it on a box, for example, then the edge is dead, and I'll have to sharpen it again right after, defeating the purpose of the test so that I can carry a "perfect condition" knife lol
 
THG said:
I don't know about that... After I sharpen my knife, I like it to be in "perfect" condition. If I test it on a box, for example, then the edge is dead, and I'll have to sharpen it again right after, defeating the purpose of the test so that I can carry a "perfect condition" knife lol
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Your metal is too soft perhaps? I don't know. I'm not too sure about low-carbon steel (if it is) or how to treat it. Afterall, I'm just a newbie... Heh.:o
 
Sengseng said:
Your metal is too soft perhaps? I don't know. I'm not too sure about low-carbon steel (if it is) or how to treat it. Afterall, I'm just a newbie... Heh.:o
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If you sharpen ZDP-189 to be able to whittle hair, after you cut down a box, it's not going to be able to whittle hair anymore but it still will be very sharp, cardboard is a real edge killer no matter what steel because it's abrasive.
 
Roger999 said:
If you sharpen ZDP-189 to be able to whittle hair, after you cut down a box, it's not going to be able to whittle hair anymore but it still will be very sharp, cardboard is a real edge killer no matter what steel because it's abrasive.
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Yeah, that's what I'm saying. If we say that right after you sharpen your knife, your edge is 100%, then after you cut anything, it's going to be less than 100%. You're not going to have a "perfect edge" once you make the first cut.
 
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