Best way of telling a knife is sharp

pete evans

Well-Known Member
When sharpening a knife how do you guys guage its sharpness. I have sharpened knives and cut strips of paper, shaved some hairs off arm etc then felt when I used it properly, this could be sharper.
If you run your finger at right angles to the blade then you get a feel for the sharpness but this is still not a definative test as I did it with a brand new scalpel today and it didnt have that razor sharp feel to it and they are about as sharp as anything. Whats the definative test?
 

procee

Well-Known Member
Got to admit I normally know by looking at it when I have sharpened it. I use the japanese waterstones in preogressively finer grades until it's a nice mirror finish, keeping the same angle as the blade was originally made with. sharp enough to take off face hair normally.

As for 'feeling' the sharpness by running a finger across the edge at right angles, what you feel here is a burr, which normally means that the knife will not be as sharp as it should be. A properly sharp knife with no burr (for example one which has been stropped like a razor) will not have a burr and therefore will not feel as 'sharp' when you run your finger at right angles to it.

Hope this is of some help - the chances are your scalpel is a lot sharper than it feels.
 

happyhunt

Well-Known Member
if you wet a patch of hair on you arm and shave some hair off, then its sharp enough for anything you would want to throw at it, simple as that.
 

ezzy6.5

Well-Known Member
My Grandad would say, 'if you can shave a sleeping mouse without him waking then it's sharp enough'.
Failing that +1 for the wet arm.

Ezzy
 

Moray Outfitting

Well-Known Member
Procee correct - the 'thumb test' will usually only really pick up that there is a feather or bur on the edge. Feels ninja sharp, but very weak and doesnt last.

Arm hair is popular and common, but strictly not really to be advised. That said I shave arm hair as a 'stunt' during my Bushcraft talks - with my axe. Always gets attention ( which is the purpose ) - especially when I then ask for a volunteer:eek: Have to say that the demonstration is actually in the context of the safety side of things.

If you can shave edges off a piece of paper in tight curls then you should be about there - often highlights if you have a dull bit on the edge as well.
 

Uncle Buck

Well-Known Member
Best way of telling a knife is sharp !!

Same as you would to tell it was blunt Pete. :D

Just Kiddin, +1 If you can shave edges off a piece of paper in tight curls then you should be about there - often highlights

if you have a dull bit on the edge as well.

Rgds, Buck.
 

nell

Well-Known Member
Lay the knife at an angle on your thumb nail,dont push just let gravity take its course,a sharp knife will not slide off,also remember a knife may be sharp in part of its cutting edge but not all the way along. DONT use the desribed method by drawing the blade across your nail.just lay it on along its length.....
 

Mat

Well-Known Member
I don't know about anyone else, but I've run out of arm hair to test with
 

nemo

Well-Known Member
After once implying that an older stalkers knife wasn't quite as sharp as it could be he replied by asking if I wanted it dragged over my bare bell end! I declined his kind offer
 

csl

Administrator
Site Staff
Lay the knife at an angle on your thumb nail,dont push just let gravity take its course,a sharp knife will not slide off,also remember a knife may be sharp in part of its cutting edge but not all the way along. DONT use the desribed method by drawing the blade across your nail.just lay it on along its length.....
Also works for fishing hooks :thumb:
 

trooper3.1

Well-Known Member
i thought this was a joke at first, how do you know if a knife sharp, run it across your throat:doh:my odd SGT used to say if you can shave a soft ladies eye brow pencil it is sharp, all i can say is ask some of the argies from the war if our blades were sharp;)

paul
 

Eric the Red

Well-Known Member
The kitchen knife makers, Wusthof, reckon you can cut a wet tissue (rather than tear it) if their blades are sharp. The demo I saw had the guy hold the tissue in one hand and cut with the other.
The only issue with paper (albeit a very good test IMO) is that it will blunt a blade very quickly.
 

trouble

Well-Known Member
i thought this was a joke at first, how do you know if a knife sharp, run it across your throat:doh:my odd SGT used to say if you can shave a soft ladies eye brow pencil it is sharp, all i can say is ask some of the argies from the war if our blades were sharp;)

paul
Your SGT , why did he have a ladies eye brow pencil ?
 

rudy65

Well-Known Member
I thought dragging it across some ones bell end would have had more effect. I know mine is sharp if i have no problems dressing out a deer.
 

Top