Testing an edge after sharpening

[abarbosa]

I am not sure if there is a thread already about methods of testing the edge.

What do you do to test if you have done a good job sharpening? Of course cutting food is the best test.

But in particular I like toothiness on an edge so I started to aim for an edge that grabs my nail like Ivan does in this video () while cutting kitchen paper towel kind of cleanly.

Most of the times I fail miserably, so either the knife grabs the nail hard and doesn’t cut paper towel that cleanly or cuts paper towel kind of cleanly but doesn’t grab the nail. There was once that I manage just using the shapton glass 500 to have an edge that excelled both at grabbing the nail and cutting paper towel.

 

[Benuser]

Cutting the finest cigarette paper gives an excellent idea about sharpness. No ragging, cutting smoothly. Hear the sound.
Another, perhaps more surprising one: plastic packing, or in my specific case a sachet containing medication: if cutting straight, there is no burr left. The slightest remaining one causes the blade to make a clear curve, AND pushes the burr entirely to one side. From there on the remaining burr is easily removed.

 

[lesslemming]

Three finger test. That’s the most reliable test for me. I also check the edge for remaining damage/chips by dragging the edge into my fingernail and inspecting with a loupe.

I rarely use paper for cutting, as it gives false positives due to false edges far too often.

For razors, it’s the famous hanging hair test

 

[Rangen]

Newsprint works. It does a much nicer job of differentiating burr-edges from clean edges than printer paper. Haven't tried cigarette paper.

 

[bsfsu]

A consistant medium, whether it is paper of what ever grade or what ever else you use. If you use the same medium all of the time you can get an understanding of what's going on with the edge.

I use printer paper for general knives and Rizla's for nice knives. I sharpen a lot and the fingernail test ends up destroying my nails, the 3 finger test is good (but it's a game of numbers as to when I cut myself ).

 

[M1k3]

Fingernail and the fingers. Paper for more stubborn knives.

 

[Pie]

How clean it cuts off a little slice of skin. When it’s done you have to pay attention.

Nothing like real world media testing.

 

[lesslemming]

Forgot to mention:

many edges will pass all your tests but will fold over quickly. An excellent test for your edge quality is to revisit your edge after a cycle of use. See if it is still sharp after that. If not, your edge was a “false edge”. This is also a good way to learn