Best way to tell if a knife is sharp?

A

adubbz

Joined
Nov 24, 2011
Messages
186
Ok, I've been wondering this for awhile. Maybe I just don't have a lot of experience in the knife world.

I am wondering how you guys test the sharpness of your knifes, and what is the exact technique you use?

Run your finger across it? Finger nail? Cut paper?
 
I like the old barbers trick. I lightly and slowly drag the edge along my thumb. If I feel the edge start to bite immediately than I know it's good. Push cutting phone book paper is another good test.
 
Though, when I'm messing around and sharpening, I like the "catch a thumbprint ridge" test for overall sharpness and the fingernail test to find dull spots.

But that's all fun. Practically, if a knife cuts what I want it to cut....then it's sharp.
 
I use a white laser pointer to shine along the edge, to check for any light reflecting back.
 
paper is good enough for me!
I'm not great at sharpening
 
I've been sharpening knives as a business for a while now and after I sharpen each knife, the final test is to hold a piece of paper in front of me (vertically) with one hand and if the knife can cleanly cut through the top of the paper without having to hold the paper still/stretched flat and straightened out, then it's good to go! Plus of course, I always make sure that the burr is removed. These are the final two things to check before I send any knife back to it's owner.
 
I like to use my arm hair. if it can pop hairs off my arm with little to no pull or friction im done. Or the old Nail trick I learned from an old school Carpenter a good sharp knife or tool will shave a fine curly sliver from your thumb nail when its is sharp, If it digs in and try to remove chunks it needs touched up. I'm a sharpning nut so I keep phone books at hand at my shaprning station so I can cup pages to see different spots on the blade by how smooth it cuts the paper at that point on the blade and you can feel friction and tiny nicks in the blade with the thin paper. I also keep a 30x jeweler's loop handy to get a up close and personal look at the edge when im sharping it.
 
dullknifeterminator I didn't know you were a member here I bought an edge pro from you 2 weeks ago thank you for the fast shipping . Good business man Wish I would of known you were on the forums.
 
but back on track i take phonebook paper or newspaper and hold it up in front of me as well and slowly slice the paper, I say slowly because I want to watch the entire blade cut the paper and if it goes through clean I have a sharp knife, but if it catches anywhere, back to stropping so that the whole edge will cleanly cut the paper with no catches.
 
If it'll pop arm hair, thats usually about as sharp as I need a knife for the work I do.
 
Push-cut newspaper to make sure I have a fine enough edge. Slice cuts on newspaper using the full length of the cutting edge, looking for snags or frayed edges (vs. a clean cut) to make sure I have an even edge.
 
If it will take the top off a bag of chips in one fast stroke without holding the bag my nephew calls it sharp.
 
I've always used the Thumbnail test. If it'll catch & hold when the edge is placed against the thumbnail at an angle, that's an indicator of a good basic edge. I usually strop it to hair popping sharp from there.
 
marcinek said:
Grab the thing you want to cut.

Try to cut it.
Click to expand...

This is the smart test. No matter what your test is when your knife cuts what you want to cut, then it's sharp.

If you want to go crazy though, hair whittling is a good test.

[youtube]K_3267AMMpU[/youtube]
 
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