When is a knife sharp enough, and how to you test?

gunmike1 said:
I have the same feeling. You are much closer to that level than me though, but hopefully with practice I can improve.

Mike
Click to expand...

You're a lot closer than me! The next thing you guys will want to do is peel an electron. I gotta have pictures for that!
 
Jeff Clark said:
I'm still trying to get a knife sharp enough. Straight razors don't satisfy me. I'm looking for nuclear fission.
Click to expand...

Nuclear fission is childs play, I once opened my Swiss army knife and cut a hole in the fabric of the universe. I don't do that anymore. :p

Seriously though, there are times when your knife should not be that sharp, If you need to do a lot of sggressive cutting it's probably better just to settle for good enough, because if you slip and hit yourself with a perfectly sharpened sharp blade, it's bye bye finger. And the bone might dent the blade.
 
Roger999 said:
I got my camera back, is this how you want it?

[youtube]9RhxwNQLW8k[/youtube]

There is a little draw in the cut because its not easy trying to cut something while looking through a 2" viewfinder.
Click to expand...

The first cut looks close, its hard to see, but is the blade horizontal ? or is it tilted a little bit with the Handel down ?
If both the blade and paper is horizontal then its what I want to see. (The first cut, not the middle ones).

Do you think you can start the cut 2 inch from where you are holding the paper ?
 
My minimum is when the blade catches on my thumbnail along it's whole length.

Best I get is slicing receipts at fast food restaurant.

I like to be able to slice paper, as my left arm needs time to regrow the hair!

I'm right at the edge of push cutting on those receipts....
 
Bare minimum when the blade catches the thumb nail.

I like to get it to slice newsprint or receipts too. It should be able to cut away a slice in quick motion w/o drag.

I like the push cut test as well.
 
Hawkings said:
The first cut looks close, its hard to see, but is the blade horizontal ? or is it tilted a little bit with the Handel down ?
If both the blade and paper is horizontal then its what I want to see. (The first cut, not the middle ones).

Do you think you can start the cut 2 inch from where you are holding the paper ?
Click to expand...
I can do it with both blade and paper horizontal, but I can't do it with the blade 2" away, the newspaper just folds.
 
Wow! What are you guys using to sharpen your knives? And, money being no object, what would you use?
 
GWashington1732 said:
if you slip and hit yourself with a perfectly sharpened sharp blade, it's bye bye finger. And the bone might dent the blade.
Click to expand...

I have done that. Right thumb is still attached, but did hit the bone, and had to take the light roll out of the edge of my knife. Severed the nerve in my right thumb.
 
GWashington1732 said:
Nuclear fission is childs play, I once opened my Swiss army knife and cut a hole in the fabric of the universe. I don't do that anymore. :p

Seriously though, there are times when your knife should not be that sharp, If you need to do a lot of sggressive cutting it's probably better just to settle for good enough, because if you slip and hit yourself with a perfectly sharpened sharp blade, it's bye bye finger. And the bone might dent the blade.
Click to expand...
I can split an atom in half! beat that! If you have an extremely sharp edge, it would be less likely to slip.
 
ziggy925 said:
Wow! What are you guys using to sharpen your knives? And, money being no object, what would you use?
Click to expand...

A lot of times, I'm using a dmt stone and ceramic stone. Sometimes an Edgepro. Money being no object, I'd like to try some cardboard wheels that RichardJ talks about, but that's about it.
 
money no object, Nakayama kiita/asagi blend with karasu, foot long natural coticule/BBW combo, Shapton 30K, Naniwa Chosera.
 
I try to keep from getting them too dull, and a Sheffield Pocket steel generally keeps 'em sharp.

It is remarkable to me how easy some knives sharpen. On some I can't help but get a rolled edge.

For really fine work I have one of the ceramics from a set and just lightly stroke the blade.
 
Roger999 said:
I can do it with both blade and paper horizontal, but I can't do it with the blade 2" away, the newspaper just folds.
Click to expand...

Yeah that's my experience too. Even when I'm able to split a hair in 3 layers I can't make a pushcut 2" away. I really don't think its possible to do so.

Still I'd love to be proven wrong on this one.

By the way Roger999, I really like the look of that stock man :thumbup:
 
It is very possible to go beyond 2" from the point of hold on newsprint. My knives that are sharpened to .05 microns go well beyond that while easily whittling the tiniest of curls from hair. It just takes practice. A better test is pushcutting the yellow pages. When you get over 2" from the point of hold it is very impressive. Something to remember about pushcutting newsprint is how different it can be from paper to paper. Try to use the same particular newspaper if possible and practice holding it with your 2 fingers so it doesn't add tension to the paper. Pushcutting newsprint requires making sure you have thoroughly deburred your edge, as your shaving edge that won't pushcut well most likely has a burr.

Mike
 
You will also find out that newpaper has a "grain". It's easier to pushcut in one direction than in one 90 deg from it.
 
I have found that sharp enough is when the knife bites me and I don't realize it until someone else asks me why I am bleeding...I gotta find a better way to determine sharpness
 
There are lots of different ways to test an edge, many of them mentioned here. Something that isn't mentioned though is that you need to be sure that this fine edge is consistent from point to heel!
Having a sharp section doesn't cut it. (Pun intended.) If you are using your thumb nail, be sure to check the full length of the edge. Same with cutting newspaper or telephone book paper.

The "RazorEdge" people sell a plastic testing device that works very, very well.
http://www.razoredgesystems.com/index.php/Products/Testers/9_Edge_Tester.html
You can perform several different types of tests with it, and it's easy to use, cheap, and effective. Even cheaper is a plastic Bic ball pen. Works almost as well but is limited to two types of tests.

Stitchawl
 
The Russians had a saying, "Better is the enemy of good enough". The application of that to knife sharpening is, after a certain point, it crosses the line into obsessive behavior.

I can get a knife sharp enough, but I still try to extract that extra level of s, often in vain. A Seki-city made "Damascus" Santoku knife I have came sharper than any knife I've ever seen. Push cutting newpaper like it wasn't there.


Does an EDC need to be that sharp? No. But you always have to try:rolleyes:
 
You must log in or register to reply here.
Back
Top