How to check if your knife need sharpening?

I use the feel test, and then after sharpening, i lightly slide the blade over the back of my head and feel for the blade to catch on the hair. You can check the full length of the blade, and any part that doesn't catch is in need of more work.

Omar
 
I like to use the push cut through phone book paper, and shaving test for my EDC knife. If it can push cut thin paper and easily shave, I know it is as sharp as I need it to be, probably sharper than it really needs to be, but that's where I like it. Everyone has their own opinion of sharp, so you will get a lot of different answers.
 
I like to keep my edges very sharp, so I mostly do maintenance on knives I personally own. If they won't cleanly slice newsprint, it's time for a touch up.

When I'm evaluating someone else's knife, I first check to see if they have a "working edge" by seeing if the blade catches on my thumbnail held at 45 degrees all along the edge. If it just slides off, it's dull. If it catches, then I'll do a finger test with the pads of my fingers to see how sharp it feels. If it feels very sharp, I'll test it on newsprint. If no newsprint is available, I'll shave my arm hair with it.

This lets me determine the level of sharpness and what, if any, work needs to be done.
 
Well, I'm a habitual sharpener, so unless I literally just finished sharpening, then in my eyes it could use sharpening.

But more realistically if it doesn't cut what you need to cut as easily as you would like then its time to sharpen. That threshold is different for everybody and some can stand a duller knife than others. In my mind there isn't anything worse than a dull knife, so I sharpen a lot...
 
My default 'test' is to get clean, effortless slicing and/or push-cutting of phonebook pages, utilizing the full length of the cutting edge. If a blade does that well, it'll also do anything else I need to do with it. I don't rely as much on shaving/hair-whittling tests as the only gauge for a good edge (burrs/wires often do that well, and individual 'hair' varies widely), but it's gravy if it will do that too, in addition to everything else.

I'm also a habitual sharpener. Almost always have a knife, hone and/or strop handy, and I'll do it just to keep my hands tuned up to the process. Also find it very relaxing, and I tend to fall back on it if I'm anxious or otherwise a little uptight. It's quite therapeutic, at times... :)


David
 
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