Ankerson
Knife and Computer Geek
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I think what he was talking about is the actual apex width.
The thinner that is the sharper the edge will be, and that can actually be measured, usually in nano meters.
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So what is the measure of sharpness to go by?
- Thread starter Eliteone2383
- Start date
I think what he was talking about is the actual apex width.
The thinner that is the sharper the edge will be, and that can actually be measured, usually in nano meters.
- Joined
- Mar 22, 2014
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- 5,366
Most peoples knives are dull. Not many keep razor sharp edges including most knife people. I blade check a lot of customers, friends, family and co workers. So far, no one had a hair whittling edge. Just excuses haha.
On average I'd say if it cuts printer paper clean its sharp enough.
For me, sharp is when the hair "pops" off when shaving. Also clean cutting phone book paper to check how consistent the whole edge is without snaging.
The effort put in to keep a tool at such sharpness is a waste of time for most. I use and strop my blades everyday. It's quite obnoxious to the average person. If many knew how much time I put into knives they might think I'm autistic hahahaha.
On average I'd say if it cuts printer paper clean its sharp enough.
For me, sharp is when the hair "pops" off when shaving. Also clean cutting phone book paper to check how consistent the whole edge is without snaging.
The effort put in to keep a tool at such sharpness is a waste of time for most. I use and strop my blades everyday. It's quite obnoxious to the average person. If many knew how much time I put into knives they might think I'm autistic hahahaha.
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Typically, the word "sharp" is used to describe the ease of cutting. There is nothing magical about a blade; it has a geometry that can be quantified and that geometry determines the perceived "sharpness." What complicates this, is that the geometry should be matched to the cutting task. For example, a straight razor edge is destroyed by a single cut through a piece of paper.
I would suggest that our perception of sharpness can be attributed to two aspects of knife geometry; the width of the apex (I think best described by the word "keenness") and the thickness of the blade behind the apex (which can be measured at various distances from the edge). I sharpening, we typically first set the geometry of the blade behind the apex - eg thinning a knife from the factory grind to a thinner grind. And second, set the geometry of the apex. The relative importance of these two parameters will depend on the material being cut.
Most of this discussion of "sharpness" is really describing what I call "keenness" - the last micron of the blade. Keenness is responsible for the ability to cut paper or grab fingerprints, shave or tree-top hair, etc. The apex may not be uniform, a property sometimes described as "toothy" but this is still a property of the last micron of the edge.
I would suggest that our perception of sharpness can be attributed to two aspects of knife geometry; the width of the apex (I think best described by the word "keenness") and the thickness of the blade behind the apex (which can be measured at various distances from the edge). I sharpening, we typically first set the geometry of the blade behind the apex - eg thinning a knife from the factory grind to a thinner grind. And second, set the geometry of the apex. The relative importance of these two parameters will depend on the material being cut.
Most of this discussion of "sharpness" is really describing what I call "keenness" - the last micron of the blade. Keenness is responsible for the ability to cut paper or grab fingerprints, shave or tree-top hair, etc. The apex may not be uniform, a property sometimes described as "toothy" but this is still a property of the last micron of the edge.
All of this "width of the apex" stuff is an approximation, unless edges hit a minimum weidth, then go to zero width instantaneously. Which they don't.
In reality one chooses a distance away ads close as they can to the apex (whereever that is) and measures the width of the blade there, based on the precision of their instruments. As Ankerson noted.
And/or one measures the rate the width increases as it goes away from the apex. That's the edge angle.
All of which, as I said earlier, is much more complicated than proton's cockamamie gross oversimplication.
In reality one chooses a distance away ads close as they can to the apex (whereever that is) and measures the width of the blade there, based on the precision of their instruments. As Ankerson noted.
And/or one measures the rate the width increases as it goes away from the apex. That's the edge angle.
All of which, as I said earlier, is much more complicated than proton's cockamamie gross oversimplication.
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- Nov 20, 2005
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The paper slicing is about what I do as far as "sharp goes". Choose another area so your weird bald patches don't show.
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- Jan 15, 2015
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All measurements have uncertainties; however, the width of the apex can be measured with sufficient precision to quantify the keenness required for shaving or tree-topping or push-cutting paper. Of course, it is not necessary to measure the apex width, since we can easily test whether the blade meets the keenness thresholds for those tasks.
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- Jan 14, 2007
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I like the bite that a slightly coarse edge has.
Grey spyderco ceramic is perfect. I think 600 grit. Nasty bite, still shaves and slices paper.
Grey spyderco ceramic is perfect. I think 600 grit. Nasty bite, still shaves and slices paper.
brancron
Gold Member
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- Dec 14, 2011
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What other area? Upper thigh? Do I have to take my pants off to test the sharpness of my knife???
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- Jun 10, 2015
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After a full day of using a knife I have 3 or so tests.
1) Can it shave?
2) Cut paper?
3) Does it catch on a sharper or finger nail.
If it doesn't pass all three it gets 5-10 passes per side on the strop. That usually fixes it right up to my standards.
1) Can it shave?
2) Cut paper?
3) Does it catch on a sharper or finger nail.
If it doesn't pass all three it gets 5-10 passes per side on the strop. That usually fixes it right up to my standards.
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- Feb 27, 2014
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- 17,936
Infinity minus 1? Well sorry to burst your bubble, but infinity minus/plus/divided/multiplied by anything is still... Infinity!
I have no idea what point you were trying to make...
Neither did he.
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- Nov 20, 2005
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Whatever floats your boat?
If you can cut your finger without really feeling the cut, it's sharp enough.
Actually, I think hair popping sharpness is over blown. It is fun of course. But I tend to like a slightly toothy edge on a knife that I use all the time for EDC stuff. For skinning or meat prep, hair popping is the way to go.
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- Apr 3, 2014
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Sharp enough to pop a blister or dig out a splinter. but not so sharp it becomes uselessly dull it's first use.
Cobalt
Platinum Member
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- Dec 23, 1998
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- 17,710
Depends on the type of knife, but factory sharp when talking Spyderco and Benchmade is extremely sharp. Same goes for my Cold Steel folders. You should be able to easily push slice through paper like it isn't even there. If you have to draw slice it isn't as sharp as it could be in a small thin blade.
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- Apr 22, 2015
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All measurements have uncertainties; however, the width of the apex can be measured with sufficient precision to quantify the keenness required for shaving or tree-topping or push-cutting paper. Of course, it is not necessary to measure the apex width, since we can easily test whether the blade meets the keenness thresholds for those tasks.
Best knife edge picture ever!
I look at my apex at 100 power with a Meiji microscope.I always wanted to see the view at electron microscope level.Thank you!
The ultimate blade would be a smart alloy which always presented a single row of atoms at the apex...resharpening as it is used like the liquid terminator!
Imagine how crazy that would be!
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What if you want a toothy edge?
I guess you can enter the menu and change the settings.
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- Dec 2, 2012
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Another thing I do, as a chef.
I place a 12" x 12" square of saran/plastic wrap on my cutting board as carefully and neatly as I can.
I'll make cuts into without wrinkling or moving the plastic wrap whatsoever. Like cutting a pizza.
On my sharpest days, i can criss cross into another cut. Most days the already cut part of the plastic will ride on my blade.
I place a 12" x 12" square of saran/plastic wrap on my cutting board as carefully and neatly as I can.
I'll make cuts into without wrinkling or moving the plastic wrap whatsoever. Like cutting a pizza.
On my sharpest days, i can criss cross into another cut. Most days the already cut part of the plastic will ride on my blade.
That really is a cool ass picture of a knife blade.
Could you turn the blade horizontally so we can see a shot of the length of the blade?
And a regular shot of the blade with a normal camera so we can see the subject blade in normal scale?
I really want to see the micro serrations everyone speaks of that gets bent over causing the 'dulling'.
Can you tell I'm a mechanical engineer getting his yayas over microscopic metallurgical imaging?
Could you turn the blade horizontally so we can see a shot of the length of the blade?
And a regular shot of the blade with a normal camera so we can see the subject blade in normal scale?
I really want to see the micro serrations everyone speaks of that gets bent over causing the 'dulling'.
Can you tell I'm a mechanical engineer getting his yayas over microscopic metallurgical imaging?