Sharpness scale from 0 to 5

Customers say that they want their knives super sharp.  I have to ask them how sharp that is, which they never could answer. Instead, I asked them what or how they cut, meat, produce, or boxes. The follow-up question was if they sliced or chopped, and if they pulled or push cut. If we had a scale from ridiculously sharp as five down to a dull 0. Let’s start with sharpness 5 which is the hanging hair test (HHT).

Hanging hair test

5 the hanging hair test

You see that this old knife doesn’t pass the test, because the hair is hanging on the edge. The pieces of cut-off hair on the paper came from that I came in with a bit of an angle lining it up. Next up is sharpness number 4, which is to smoothly slice cigarette paper from heel to tip or push cutting it.

cigarette paper slicing

cigarette paper cutting with knife tip

cigarette paper cutting with knife heel

4 cigarette paper cutting

As you see the old knife passes this test, the only thing was that I felt a light resistance at the back and of the heel starting. This is too sharp for a kitchen knife, except for single beveled knives, and delicate fillet knives. 3, which is that it should be able to push-cut Para-cord without a problem from heel to tip and be able to shave hair.

Push cutting paracord easy 1

Push cutting paracord easy 2

Shaving hair

3 shaving hair and push-cutting paracord

These tests are passed easily; 3 is a good sharpness for most thin kitchen knives like slicers, and fillet knives. Sharpness 2 is to slice magazine paper from heel to tip, slowly, and smoothly without any snagging.

Slicing magazine paper easily and smoothly

2 Slicing magazine paper smoothly

This knife is almost too sharp for this test I’m pretty sure the paper will dull it. 2 is good for medium, and heavy-duty kitchen knives. Believing that most people would be comfortable with 2 sharpness of their kitchen knives. To be able to slice ordinary printing paper, cutting into the side of a tomato or lemon without slipping is the lowest sharpness.

Slicing lemon paper thin

Slicing printing paper smooth from heel to tip

1 Slicing magazine paper

This is still a good sharpness for your heavy-duty kitchen knives and cleavers. If you don’t pass the test, your knife is dull and needs sharpening. I call this sharpness number 0.

Sharpness:       Test:                                                    For:

5                      Hanging hair test                                 Straight razors

4                      Slicing cigarette paper                         Delicate slicing knives

3                      Push cut Para-cord, shaves                 Thin kitchen knives, fillet knives

2                      Slicing magazine paper                       Most medium kitchen knives

1                      Slicing printer paper smooth               Heavy kitchen knives and cleavers

Other sharpness testing is better but takes more skill and danger

Finger nail tests, Does it dig into the nail and grab it? Does it slide smoothly over the nail? If put a low angle against the nail does it stay? The test could all be modified, and be done with a plastic pen but with less feedback.

Slice test, Hard rolled Kleenex, wet rolled towel, tomato slicing, hemp rope slicing, slicing into the side of a standing toilet paper roll.

Thumb test, feel for burr, feel how much it sticks to the finger.

Machine test, Njut, Catra, Bess, Lasergionometer.

Magnus Pettersson hand knife sharpener

1423 Euclid Street, Santa Monica, CA 90404

To request sharpening call or text 310-486-6068 or email.

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