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How do you test sharpness in your blades?

V

Vegas Blade

Joined
Feb 9, 2012
Messages
902
Did a quick search, and didn't see anything on this. Seems like it should have come up.

Anyway, how do you all test for sharpness?

There is the shave test, the paper slice/push cut test, the hanging hair etc.

I use a S shaped push cut through phone book paper with my polished edges. I will also see if it will make "fizz sticks" on a hair. (My wife's brushes come in handy for this. :-) )

For my more toothy edges I use a draw strike through phone book paper. It will still cleanly slice at a 400-600 grit.

What tricks do you use??
 
I just use the shaving test. If it is enough to cut a clear path in my arm hair in a single swipe, then it is all the edge I need.
 
Slicing phone book paper with the length of the blade works for me. Occasionally I'll make sure it shaves arm hair but those bald spots grow fast! :eek:
 
There's the three finger test where you press three fingers into the edge carefully with the thumb on the spine to help control.

Me, I like running the blade against the tip of my finger and see how it slices into the upper skin layer.
 
Arm shaving, phone book cutting and fingernail test.
Clean shave of the arm
No "catching" as the blade slices through the paper
"Catches" the fingernail with just a light touch and doesn't move in either direction
 
I used to use all of those tests before. These days, I just feel the edge. By now, I can feel my edge with my fingers and usually be able to tell how it will do on those tests.
 
singularity35 said:
I used to use all of those tests before. These days, I just feel the edge. By now, I can feel my edge with my fingers and usually be able to tell how it will do on those tests.
Click to expand...

Me too... If it grabs real good I know it's sharp.
 
i like dulling my knives in use. very bad knives dull in storage. but anyway, during progress sharpening: after medium grit, it must already "bite" the skin on the finger tips, meaning it's already sharp by most people's standards. this tells me i was able to apex correctly at the start. when i go to the fines, first it must be able to slice paper (any paper) with ease. after lapping/stropping, it must be able to push cut paper (any paper) with ease.

failure to split hair towards the follicle end means additional dry stropping.
 
Same as most posts here.
Shaving: rough shave vs smooth shave
paper: phonebook or wax paper, s-cuts
fingernail
finger

One thing I do that hasn't been posted yet is to inspect the edge under a bright light. A slight reflection on the edge is still enough to rough shave; it's certainly past working sharp. Once I apex it enough that there's no reflection it's usually smooth shaving sharp.
 
My go to tests are shaving and phonebook paper Though I'm thinking more and more that the shaving test, while fun and impressive, doesn't really test much that's useful.

Phonebook paper cutting seems to reveal inconsistencies, overall sharpness, and the existence of burr or burr remnants. I really like BluntCut's phonebook paper advice: Cut the paper with at least 10 full strokes. A really sharp blade will keep cutting and cutting paper, but if you have a burr that's been stood up, it will fail by the 10th cut and start hanging or tearing the paper. I have to admit that I tried his test and had a blade or two fail on it! He's got a great video showing this test combined with his wooden dowel burr removal technique. Both are worth studying and applying.

I've said it before and I'll say it again: BluntCut doesn't use a lot of words, but what he says is VERY MUCH worth paying attention to.

Brian.
 
I usually just grab a piece of paper off the printer and slice it a few times or shave a little spot off my arm
 
For knives, I will look at the edge to look for areas where light reflects. If I can't see any, I will double check with thin paper.
If I am honing my straight razors, I will shave my arm hair as I progress and then test shave before putting away my stone.
 
If it'll push cut 550 Paracord without effort and grab at my fingers when gently passed across the edge then it's sharp enough for me.
For the uses I have I much prefer a toothy edge.
 
Rey HRH said:
There's the three finger test where you press three fingers into the edge carefully with the thumb on the spine to help control.

Me, I like running the blade against the tip of my finger and see how it slices into the upper skin layer.
Click to expand...

I thought I was the only one that did this. Haha.
 
Many videos show the "Paper Test." Has anyone done the tomato test. Hold a tomato in your hand palm up and if you can slice it with no major pressure then you have a sharp knife. My late grand father always checked his knives this way. ;)
 
KG4ULR said:
Many videos show the "Paper Test." Has anyone done the tomato test. Hold a tomato in your hand palm up and if you can slice it with no major pressure then you have a sharp knife. My late grand father always checked his knives this way. ;)
Click to expand...

I've seen that on YouTube several times. They take a paper thin slice off a tomato resting on a cutting board. In one in particular, he did the same thing with a grape. Now imagine something so small that moving it takes hardly any pressure. Yet he sliced a paper thin cut off of it, more than once. He even dropped a tomato, and subsequently a grape onto the knife blade from six inches up, both cleaved cleanly.

I adore some great kitchen knives, but I've never had any NEAR that kind of sharp.

EDIT: And here is said video ...

https://www.youtube.com/watch?v=7sQGKAVWbIg
 
Last edited:
bgentry said:
My go to tests are shaving and phonebook paper Though I'm thinking more and more that the shaving test, while fun and impressive, doesn't really test much that's useful.

Phonebook paper cutting seems to reveal inconsistencies, overall sharpness, and the existence of burr or burr remnants. I really like BluntCut's phonebook paper advice: Cut the paper with at least 10 full strokes. A really sharp blade will keep cutting and cutting paper, but if you have a burr that's been stood up, it will fail by the 10th cut and start hanging or tearing the paper. I have to admit that I tried his test and had a blade or two fail on it! He's got a great video showing this test combined with his wooden dowel burr removal technique. Both are worth studying and applying.

I've said it before and I'll say it again: BluntCut doesn't use a lot of words, but what he says is VERY MUCH worth paying attention to.

Brian.
Click to expand...

^ 2nd !!
 
My test is slicing easily through very thin glossy magazine paper, especially a sheet rolled into a loose tube. A Sports Illustrated works well.
 
I slice the thin shiny paper that advertisements in the Sunday newspaper use. Catching the edge of the paper to initiate the cut is the hardest part.

I'm not a sharpening expert and don't need a really sharp blade for normal use but if I can cut the shiny paper the knife will be sharper than I need.

FWIW I sharpen with the diamond stones of a DMT Aligner system and then a few quick strokes with a homemade strop.
 
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