Testing the edge?

babakanoosh45

babakanoosh45

Joined
Oct 6, 2006
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What are you folks doing do check for desired edge sharpness after a sharpening? I have read of the arm hair shave/ the kindleing split and others. I most often try to shave the thinnest slivers I can from a sheet of paper. Or if I am work I may try to cut through a .040 sheet of PolyPro sheeting, this is a tough test! I am always looking for knowledge about all aspects of knives and the maintance there of. Any resopnse will be appreciated... ~baba~
 
I found a few thousand index cards in a stash of leftover school supplies my mom had purchased, so those are my standard now. I push cut those and exanime how smooth the cut was and how much force was required.

Not using any outside materials, I'll see how easily it shaves arm hair. Also, my general edge test is to push it on the top of my thumb, in between the first and second knuckle. It's bony and sensitive there, which is good for measuring pressure. Works much better for me than using the pad of my thumb like I've seen most people do.
 
Shaving my arm and cutting thin paper (e.g. magazines, newsprint). I try and make a really thin cut on the paper and try and get curly-q's with the knife edge. If I can do that without much resistance then it's sharp. Also, thin paper lets me feel if there are and burrs, chips, rolls, or unsharpened/unpolished places on the blade. The less pressure I use for either my arm hair or paper tells me how sharp it is. And MAN do I love to see that knife glide through paper and the hairs on my arm get up and run away!

:D :D :D
 
I use my dog. I have to admit he looks a little funny with all those little bald spots but he doesn't care
 
I usually just shave my arm hair. After awhile you can feel how it's pulling on your hair and get a pretty good idea of how sharp the edge is.
 
Vivi said:
I found a few thousand index cards in a stash of leftover school supplies my mom had purchased, so those are my standard now. I push cut those and exanime how smooth the cut was and how much force was required.
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I don't throw away business cards. I push cut them too. If the card bends under pressure then it is back to the sharpener or steel.
 
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I hold newsprint between the thumb and forefinger of my lefthand. I then, touch the blade, verticaly to a point about an inch away from the fingers, and gently press straight down with the blade. If it cuts straight down the newsprint, withoput ANY slicing motion, I consider it sharp.
 
I let the edge ride along my thumbnail with just the weight of the blade creating pressure (not talking machetes here:) ).

Tells me what I want to know usually. I think the hair shaving thing is over rated myself. It does imply sharpness, but I don't do a lot of shaving with my knives, and sometimes I want a more aggressive, and less razor-like edge for utility cutting. Just my personal .02. Some folks like to shave a lot.;)
 
My post-sharpening examination is equal parts feel with my forefinger and just looking at the edge. I have gotten pretty good at being able to gauge sharpness just by eyesight.
 
A few years ago I did alot of the sharpness tests in a thread like this one, with a knife I sharpened around 50 degrees per side, 100 degree total, and it passed almost all of them but it really didn't cut worth a dam. Sharpness is a funny thing. :)
My main sharpness check involves both sliceing and push cutting paper towels. For the slice I roll it up very tight hold one end and slice off the other end. For the push I try and cut a strip off the roll, that strip is what I roll up tight.
 
db said:
A few years ago I did alot of the sharpness tests in a thread like this one, with a knife I sharpened around 50 degrees per side, 100 degree total, and it passed almost all of them but it really didn't cut worth a dam.
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Sharpness isn't a direct measure of universal cutting ability, cutting ability is proportional to an inverse of a bunch of addititative factors so if one is really off (angle is high) the cutting ability will be very low unless the proportionality constant for that factor is low (the material isn't binding). Swaim showed this on rec.knives many years ago and Talmadge detailed this in several posts here and on knifeforums, it is even detailed in the FAQ linked in this forum. This was in fact one of the main complaints about Benchmade, they were very sharp but didn't cut very well because the angles were too obtuse. Ironically, the inverse is made about Opinels, they often cut very well when new even though they are often not very sharp. Maybe the two companies should get together on a knife.

-Cliff
 
fewpop said:
I let the edge ride along my thumbnail with just the weight of the blade creating pressure (not talking machetes here:) ).

Tells me what I want to know usually. I think the hair shaving thing is over rated myself. It does imply sharpness, but I don't do a lot of shaving with my knives, and sometimes I want a more aggressive, and less razor-like edge for utility cutting. Just my personal .02. Some folks like to shave a lot.;)
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You can actually get a shaving edge with a very aggressive edge. With my DMT X coarse I was able to get an edge that would shave and push cut newsprint, albeit a little roughly. I remember reading that Cliff Stamp used a 90 AO hardware store stone on AUS 4 and AUS 8 blades and getting edges that lasted forever on cardboard, but were also capable of shaving and push cutting newsprint easily. I think it's just a matter of getting the edge to form clean.
 
I reprofiled my Benchmade 710 D2 to 15 degrees per side. I sharpen ONLY with the grey rods on the Sharpmaker, and I get a very aggressive slicing edge that will zip through a seatbelt, but will also pushcut newsprint.

Pushcutting doesn't necessarily mean a polished edge in my experience. And yeah, it's a lot of work, but IMHO, it's darn well worth it.:p
 
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