Levels of sharpness? Sharpness tests?

R

Remy

Joined
Jun 7, 2005
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As I get more and more into sharpening, I'm trying to figure out more and more ways to determine how sharp my knife is. I'm wondering if anybody has come up with an informal "levels of sharpness" list or something like that. I'm familiar with things like being able to shave, push cutting paper, and cutting hairs. Anybody else have some good tests? At what point do you say it's "sharp enough" or maybe even "too sharp?" Obviously this would vary based on the intended use of the knife, so I'm mainly referring to EDC type knives. Sorry if something like this has been asked before, I searched and couldn't find anything.
 
first test is after the 400 grit stone it should be able to easily slice paper. After the 800 grit stone my knife should easily slice newsprint and shave hair. After taken through the 1500 grit polish tape and stropping, it MUST whittle hair. Thats for me anyway
 
Your fingers are the best testers of sharpness. They will tell you more than any cut test.
 
All my knives are polished on an 8000 and soon to purchase a 10,000 and 12,000 grit.

they must split my skin instantly or I keep polishing.

my sharpest knife (yanagi) will slice through printer paper without making much noise. Of course all sharp knives can slice printer paper, slicing it without noise is extremely sharp. I rarely touch this edge with fingers for obvious reasons.
 
Good question. I'm always looking for new "tests". Shaving hair doesn't work for me because since I really got into sharpening a few months ago, I don't have any hair left!! :). Honestly, I can get a TON of feedback from the fingernail test. Not just IF the knife will grab the nail, but HOW it grabs the nail and at what angle. If my edge will really "stick" in the nail at low angle and light pressure then I have a pretty accurate idea where it's at. Of course I test it on newsprint and look for a square inch or two of hair somewhere on my body, but I have a pretty good idea just from the nail test.

Someone said the other day you could kind of pull the edge across the back of your head like a comb and see if it grabbed the hair. I was using this a little until I tried it with my bd1 manix (which I always am able to get silly sharp). I pulled it lightly across the back of my hair and a HUGE clump of hair bounced off my shoulder and fell to the floor. Oops!
 
I always start with 3 finger sticky, then how will it cut newspaper across the grain? If a fairly coarse edge it should draw cut in stages cleanly from one side to the other and easily finish, even if the paper has flopped over. If a mid range edge it should pushcut end to end but with some noise and still draw very well. If a fine edge it should cross cut with very little noise, and cut a circle out of the paper (about 2-3" diameter), cut a wavy line etc. It will likely be loosing some draw cut advantage at this stage, but will treetop some hair and be very close to whittling.
Another hasty test is to see how well it parts freehanging paper towel with a very shallow swat using only the belly, no tip. Follow up with a push/shear cut across the paper towel. Take the pieces and twist into a tight "rope", rest the edge on it and execute a draw - how well does it catch and dig into the "rope". The paper towel testing is heavily influenced by the brand and geometry, but still useful.
 
Some good ideas here. I definitely need to train my fingers more to feel an edge. After reading some of these, I also think I need to get my knives a little sharper before moving on to the finer stones! Another test I saw (for a chef's knife) was dropping a tomato over the blade and having it split in half cleanly. Looks fun!
 
Slow !! cutting phonebook paper in curves without dragging/ripping, catching my chest hair easily without touching skin (I know it's gross ...). Then dragg the edge sideways over a wooden stick (gently, not destroying the apex) and try again.
 
awestib said:
Slow !! cutting phonebook paper in curves without dragging/ripping, catching my chest hair easily without touching skin (I know it's gross ...). Then dragg the edge sideways over a wooden stick (gently, not destroying the apex) and try again.
Click to expand...

:cool: High confident sharp clean edge :thumbup:
 
I have found that phonebook paper is a cheap and easy test of how an edge is progressing. One or two swipes across a page will readily show audibly how sharp and smooth a knife is and will snag if there are any areas or artifacts not sharpened. Make sure you pay attention to trying both ways, with and against the grain.
 
It's sharp enough when I can do this...
20131004_215957_zpsd9444443.jpg
 
What is 3 finger sticky?*

*nevermind, looked it up.

there is NO WAY I will do that test, edge too sharp.
 
HwangJino said:
What is 3 finger sticky?*

*nevermind, looked it up.

there is NO WAY I will do that test, edge too sharp.
Click to expand...

No edge is too sharp for that test not even straight razors.

In reality the sharper the edge the easier the test becomes.
 
wow. none of my knifes have ever touched a stone. i use a deburring wheel with a fine polish with green rouge on a buffing wheel. under a comparitor there are no marring marks. spotless and beyond razor sharp.
 
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