How do you test for dullness?

Just wallop someone on the head and if the blade cuts into the brain, it's sharp enough.
 
For most knives I check on the thumbnail. For ones I expect to be very sharp I test how it catches arm hair. While sharpening I test it on thin glossy magazine paper.
 
If it won't pop hairs with almost no pressure it gets stropped till it does. I never let a knife get dull. Worthless.
 
Simple for me....

When there's a material I cut a lot, let's say cardboard, I know how my knife should feel through that material....If there is more resistant than I would like there to be, and more then I am used to, it's not sharp enough for me.

I will then confirm that by feeling the edge, and maybe slicing a little PB paper to see what I need to do to get it back to what is optimal for me....
 
When it feels dull by my standards while cutting something it needs to be sharpened. Now how I go about testing for sharpness and it hitting my standards while sharpening is a whole different subject, but lets just say I have high standards.

Used to be a lot more picky about never letting a knife get dull but after having to use a box cutter at work (Gerber EAB) instead of a knife and just maintaining the blade on that I've learned to stop having such high standards as to when to sharpen it when it gets dull as it dulls a lot quicker than most of our knives. Plus I may have been having problems with it being too sharp and cutting through boxes instead of packing tape a little too often with no pressure being used as I couldn't even run the blade along the edge of the cardboard without cutting it, so I ended up having to dull the blade a bit to stop having that issue. Lets just say my time in MT&E was not wasted.
 
brancron said:
For most knives I check on the thumbnail. For ones I expect to be very sharp I test how it catches arm hair. While sharpening I test it on thin glossy magazine paper.
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Same here. To me the glossy magazine paper is better test than pb paper, albeit very marginal glossy mag paper tears alot easier than pb IMO. I've detected a slight burr on mag as where pb would slice fairly well.

My wife keeps wondering where her US weekly disappears to :rolleyes:
 
On my thumbnail. Simple to do and a clear indication if it has an edge or not, ie does it need a sharpen.
After sharpening comes the A4 paper test, to feel any missed damage along the edge.
If I'm being very fuss with sharpening a knife, I finish with the cut a paper towel test. Not often I get a knife to clearly past this test.
 
I do a combination of the thumb drag and the 3-finger test. Across the blade and never down the edge, mind you. Gives me the heebie jeebies when friends test my knives that way. They only do it once, then need a band aid and never test my knives again(haha!) But what's funny is I use this technique when sharpening on the wicked edge before progressing to a finer stone. After sharpening a couple knives in one night, the ridges on my fingertips get so worn down so after a while I can't discern sharpness and start questioning my edge quality. So I try the nail technique and it grabs like no tomorrow and shaving paper and it cuts like a light saber thru hot butter.

Moral of the story--- become proficient in, and have multiple test methods should one give you a questionable result.
 
stog75 said:
I do a combination of the thumb drag and the 3-finger test. Across the blade and never down the edge, mind you. Gives me the heebie jeebies when friends test my knives that way. They only do it once, then need a band aid and never test my knives again(haha!) But what's funny is I use this technique when sharpening on the wicked edge before progressing to a finer stone. After sharpening a couple knives in one night, the ridges on my fingertips get so worn down so after a while I can't discern sharpness and start questioning my edge quality. So I try the nail technique and it grabs like no tomorrow and shaving paper and it cuts like a light saber thru hot butter.

Moral of the story--- become proficient in, and have multiple test methods should one give you a questionable result.
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For whether or not it's time to proceed to the next stone or when I am done sharpening I find that if you use a sharpie and mark up the bevel it's a good indicator especially with a jewelers loupe as you can stop places were you haven't hit it. This is especially true with a guided setup. On top of that a 3 finger sticky test, for me im feeling for imperfections and that little voice in your head to yell at you to not move your fingers even the slightest bit or you get cut the very moment you barely tough the edge with no pressure. And just simply drawing it slowly through receipt paper and push cutting seeing if I can find defects that way. I found the thumb drag across the blade did nothing for me in discerning how sharp a knife is once I got to a certain level of sharpness so I stopped early on once I really started trying to learn how to sharpen. It was same story with seeing if it caught on my thumbnail, as those levels of sharpness are easily obtained and I have knives which can pass either test which are not even fully apexed yet.
 
Make sure you're in a well-lit area and open the knife and hold it with the spine down, so that you're looking at the blade grind. Move the knife side to side a little bit and if you see light catching on the blade, what you're actually seeing are dull spots along the blade. This method is a bit more difficult, but it keeps your fingers out of the equation. I find that the paper cutting test can be a little inconclusive, i.e., any reasonably sharp blade can cut paper and it takes a little skill to feel how well a blade is moving through the paper.
 
Drape a piece of phone book paper and see if you can cut into the top... or how far away you can cut it from where you are holding it.
 
If it cannot be batoned through zucchini, then it needs to be sharpened :D
 
If just picking up a knife and checking to see if it's sharp, I kinda do Murray Carter's 3 Finger Test but do what he says not to do - I ever so slightly drag my fingers across the edge, not along it. The way the edges bites immediately tells me 'very sharp', 'sharp', or 'dull'.
 
I cut what I normally cut all day, cardboard.

I like it to glide through, if i feel any snags or dragging, I'll sharpen.
 
Korben_Dallas said:
.......To me the glossy magazine paper is better test than pb paper, albeit very marginal glossy mag paper tears alot easier than pb IMO. I've detected a slight burr on mag as where pb would slice fairly well.....
Click to expand...

A knife that will clean cut phone book paper is going to be sharper than an edge that cuts stiffer coated (glossy mag) paper stock. The flimsier the paper that a knife clean cuts, the sharper the edge...all things being equal. Make sense? The ultimate test being a single ply of Kleenex or Charmin--but good luck with that.

Also, that coating on glossy mag paper is clay and other nasty stuff (added for increased light reflection, making those pics purtier) that technically will dull your edge much faster--which may be those "burrs" you are feeling.
 
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