edge bevels are not edges

hardheart

hardheart

Joined
Sep 19, 2001
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Just wanted to maybe discuss this a little. Sometimes I see things about getting burrs on 'both sides' or sharpening on one side, then sharpening again on the other. The bevels don't cut, the edge does, and on the most common of knives, you only have one edge (forgoing double edges and fancy profiles for convenience and, well, irrelevance) That means you form that one edge, sharpen one time, maybe only get one burr. A buddy of mine can get a wide edge bevel to a mirror finish. Unfortunately, most of the time the knife wouldn't scrape hair. He's gotten better, using a spare waterstone I gave him instead of the Lansky (the clamp works, but only when you make it, as far as angle matching and such). Still, he was looking at the bevel, not the edge. You have to check the edge itself if you want to cut stuff.

Wide, narrow, shiny, frosty, wavy, straight, a naked eye look at a bevel really doesn't tell me if a knife is sharp. What do you guys think?
 
With my relative limited experience sharpening compared to a lot of guys here I agree.

If I am reading right the very edge where the two bevel surfaces meet does the cutting. The goal is to have that very edge where they meet to be as narrow as possible. They need to meet in as fine a line as possible.

The polished bevels and the low angles will help slice and go through what you are cutting efficiently. But it is the very edge where the bevels meet that does the actual cutting.
 
Edge bevels are not edges. Except when they are.

I think we aren't always precise or consistent in our terminology, which probably is very misleading to lots of folks, and cause of never ending pedantic threads.
 
A 'Sharpie' marker is the sharpeners friend when it comes to making sure that it is the 'edge' being sharpened and not the 'bevel'.
 
IMO the finish on primary and/or back bevels doesn't affect cutting performance. I suppose some would argue that it does, at least indirectly, because using a finer grit when establishing or re-honing the primary bevel affects the size and depth of the "tooth" of the edge. But if you're applying a microbevel afterwards, which I always do, it becomes irrelevant, except that the coarser the finish on the primary bevel, the more work required to add the microbevel at the desired level of finish/fineness -- but still, microbeveling provides a huge savings in time and effort compared to polishing the primary bevel.

I also agree you can't tell much about the sharpness of an edge by looking at the bevel with the naked eye, unless it's a really poor sharpening job and there are still gross imperfections or damage to the very edge. Under magification I've measured the average "tooth" depth of an edge honed at 12 deg./side on medium AO, about 240 grit, to be approximately .0005" (this is using a good deal of care and very light pressure to finish.) I certainly can't see this with the naked eye, and such an edge feels sharp to common fingertips or nail tests. But applying a microbevel with fine ceramic (1200 grit equiv.) to where the edge looks almost perfectly smooth at 40x magnification makes a substantial difference in sharpness as measured by push-cutting. Of course you can usually see the microbevel without magnification, but the naked eye still can't determine how fine the actual edge is.
 
Yeah the edge is the edge and the bevel is the bevel. I do believe and am one of those people who thinks what is behind the edge does greatly effect the cutting performance of a knife. However, what your cutting will also determan how much behind the edge will be a factor.
 
db said:
Yeah the edge is the edge and the bevel is the bevel. I do believe and am one of those people who thinks what is behind the edge does greatly effect the cutting performance of a knife. However, what your cutting will also determan how much behind the edge will be a factor.
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It used to seem intuitively obvious to me (and still does somewhat) that bevel finish might make a difference in how well a blade cuts some materials, particularly anything that would bind right behind the edge -- but then, it seems binding materials, or at least some, might "stick" more to a polished surface than a rougher one. I've never really tried to test this, and can't say I've ever noticed this effect in normal use.
 
Dog of War said:
It used to seem intuitively obvious to me (and still does somewhat) that bevel finish might make a difference in how well a blade cuts some materials, particularly anything that would bind right behind the edge -- but then, it seems binding materials, or at least some, might "stick" more to a polished surface than a rougher one. I've never really tried to test this, and can't say I've ever noticed this effect in normal use.
Click to expand...

Like a granton edge on kitchen cutlery should reduce slices of food from sticking to the blade?
 
My name is Jim and I am a bevel polisher.

"HI JIM"

I think a highly polished bevel is a natural result of a highly polished edge.

Few would argue that as a absolute measure a finer edge can be made thinner and therefor sharper than a course one?

The formula looks like this to me.

Must haves:

Thin polished edge
Thin relief bevel behind edge

Optional:
Highly polished relief bevel
Polished primary grind


Of course all of this becomes moot if you do a nice Convex edge like God wanted you to. :D
 
the knife is sharp when it will cut without much effort, and for a reasonable amount of time reguardless of what it may look like.
 
DOW I'd agree there probably is alot of different variables to the effect of polish and thickness behind the edge that effect cutting performance. One that I have personally noticed is a polished edge bevel seems to have a noticeably less amount of sticky tape goo stick to it than a coarser finished bevel. However, slicing a tomato I notice no difference between a polished and a coarser finished bevel.
 
Okay here is a good 'fer instance...' The one on top is an original unaltered US Army Quartermaster knife. Underneath it is someone's sad attempt to make a dagger of it. When I acquired it via Ebay the seller showed a picture of it in its sheath and described it merely as knife shows some use and sharpening but handle is tight. Needless to say had I seen the photo I would have passed it by, and $32 and a few days later I was a little annoyed. Part of the joy of Ebay. The bottom knife was easily the dullest knife I had ever purchased, with the possible exception of some butter knives. The individual who did the damage managed to get a totally different bevel on each side of the knife so nothing was even. A convex bevel on one side and a flat one on the other. No edge. With stones I eventually got it to shave my arm sharp, but was still not happy as it was a barely that sharp.

Cattarugus.jpg


Then a friend mentioned he had a belt grinder.. A few days later and at least the left side is now equal to the right.

CattRedone.jpg


A few hours later with a whole series of stones and a strop and this 'ugly duckling' is easily currently one of the sharpest knives I have ever owned (and I have had many). It is still handle heavy (and I will fix that), but oh wow, is it sharp. Can (and has) easily make a long hair look like a fuzz stick.

As an aside, when we go to the web sites where diamond scalpels and similar devices with blades only a single molecule thick are sold, we see that friction above the cutting edge against the items being cut becomes an issue. That friction reduction is where the shaping and polishing of the bevel makes a difference. We, with the gross cuts we make of tomatoes and similar with our large strength, rarely notice the difference, but trust me, way down low, at the cellular level, the polished bevel cuts better than the non polished one, simply because it offers less friction to the material being cut. We could probably see this by magnifying the things we have sliced and viewing what makes a ragged cut and what makes a smooth one.
 
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