tall tales of sharpening.

Tai Goo said:
In a very real sense, sharpening is a test. You can tell a lot by the way the burr and edge behave.
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Very interesting remark, and a keen insight IMO, Tai. Cliff and I briefly discussed much the same thing in a recent thread .... essentially that excessive burr formation indicates a blade that really isn't worth the extra effort to sharpen.
 
Tai Goo said:
The knives in the pics are 1095. It's a little bit harder to get that type of edge on 1065 or 5160.
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In what way?

However,... I don't consider "steel selection" and "heat treating" as parts of the sharpening process.
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They influence methods for me and the goals as the angle and grit are usually optomized for the steel as the geometry is so ground as well. For example if I compare 1095 at 66 HRC vs 420J2 at 50-55 HRC then the 1095 can be ground much more acute at the edge which means it can slice as well with a higher polish. The 1095 will also have far less issues with burr formation/removal, usually nothing specific is required, but a lot of care needs to be taken with the stainless as it will tend to burr readily and can be difficult to remove.

What I look for is a blade that's easy to sharpen,... AND holds an edge well.
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I have found that a blade which is very easy to sharpen, easily takes a crisp edge with little to no burr issues tends to have strong edge holding, assuming you are talking about keeping that high level of sharpness. A softer steel with a lot of carbides can however though its heavy wear resistance stay at a low level of sharpeness for a long time but be a real mess to sharpen.

-Cliff
 
Dog of War said:
Very interesting remark, and a keen insight IMO, Tai. Cliff and I briefly discussed much the same thing in a recent thread .... essentially that excessive burr formation indicates a blade that really isn't worth the extra effort to sharpen.
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If you get a wide course burr that peels off as a wire easily, it's not so good. On the other hand, if you get a tiny micro burr on a very fine stone that springs back and forth and is difficult to remove, it's a good sign. Most of the time I don't see any burr peeling off the edge, it's either so fine I can't see it, or it's being abraded away.

If the edge has a rough toothy or gritty feel after stropping, it’s not so good. If it feels smooth the whole length of the blade, it’s a good sign.

...At least for the type of edge I'm after. :)
 
The burrology! :)

A lot of the time, I get a tiny micro burr that you can flip back and forth with your fingers until you get tired of doing it. It's as though magnetism was holding it on.

If I hone only to a fine Norton bench stone, I can flip that burr back and forth on a course strop almost indefinitely...

As a side note however, I raley go above about a Rockwell 58.
 
"A lot of the time, I get a tiny micro burr that you can flip back and forth with your fingers until you get tired of doing it. It's as though magnetism was holding it on."

I guess with that statement I should add that I strop the edge until I can't feel or see any burr.

"If I hone only to a fine Norton bench stone, I can flip that burr back and forth on a course strop almost indefinitely..."

... and I should add that with that type of burr I hone it down on finer stones and then strop it until I can't see or feel any burr.

What exactly happens to the burr is still a mystery to me, whether it comes off or whether it's just reduced and aligned? The only real difference between a burr and an edge that I can find a definitive answer to is that a burr is “J” shaped and an edge is straight.

Also, most of my blades are between a Rockwell 56-58, which is just a personal preference for the types of knives I like to make.

It's been an interesting discussion,... but I have to get back to work. :)
 
Tai Goo said:
If you get a wide course burr that peels off as a wire easily, it's not so good. On the other hand, if you get a tiny micro burr on a very fine stone that springs back and forth and is difficult to remove, it's a good sign.
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I think it is better to have that type of burr than the former but ideally you don't have any burr movement of that type. When you have the edge folding around it just shows that the steel is too weak to withstand the abrasion and deforms instead of getting cut, so either the grindability or the hardness should be higher, ideally both. Burrs can be cracked off, or ground off, depends on the steel and how they are removed.

-Cliff
 
O.K. I'm on lunch now.

The only other fact that I've been able to find about burrs is that...
..."Whenever a piece of steel is cut or abraded some type burr is formed."

In my theory, the burr consitsts of "smart" particules of steel that stick the stock and "slide" out of the path or angle of the abrasion. It's not formed by bending or folding, but by cutting or abrading.

It's very mysterious. I guess that part of sharpening is...
 
Everything seems to effect the burr. It behaves differently with different steels and hardnesses.

I guess it just depends what kind of blade you are after, what you like and what methods/tools you like use. What's better or best, really depends on the working concept of the individual. There's always a few trade offs.

The main point is to pay attention to how it behaves and what it’s doing.
 
You can see burrs form in Verhoeven's work and that they get larger once the steel no longer has the strength to resist deformation, he is of course working on machines which have vibration issues but the same principles hold in general. You can see this directly by just consider what an edge would look like if there was no deformation or fracture larger than the abrasive cut track. The edge would then form to the limit of the carbide/grains and thus the burr would be minimal, 0.1 microns or less. The main burrs people see are deformation driven, you can also see this in some photos such as Pam has taken where there are big pieces of steel which were not abraded. This is also why they form much easier under smaller contact surfaces because the pressure to form them is much higher. You can also get debris from the abrasive/steel, but that comes off pretty much immediately with the next pass of the finer abrasive.

-Cliff
 
I agree!

The final “leading edge” or boundary, is either of a fractured or abraded nature.

What else could it be?
 
Tai Goo said:
If you get a wide course burr that peels off as a wire easily, it's not so good. On the other hand, if you get a tiny micro burr on a very fine stone that springs back and forth and is difficult to remove, it's a good sign. Most of the time I don't see any burr peeling off the edge, it's either so fine I can't see it, or it's being abraded away.
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Most the knives I use anymore don't even require a separate burr removal step, I just go directly from sharpening the primary on a medium stone, to applying a microbevel with fine ceramic CrockSticks or Sharpmaker.

Those that do need some extra "attention" to remove a minute wire edge just get a couple light passes on the ceramic at an elevated angle, maybe 40 deg./side or so (Jeff Clark's method.) If that doesn't get it, I've learned it's probably a lost cause.
 
Tai Goo said:
"A lot of the time, I get a tiny micro burr that you can flip back and forth with your fingers until you get tired of doing it. It's as though magnetism was holding it on."

I guess with that statement I should add that I strop the edge until I can't feel or see any burr.

"If I hone only to a fine Norton bench stone, I can flip that burr back and forth on a course strop almost indefinitely..."

... and I should add that with that type of burr I hone it down on finer stones and then strop it until I can't see or feel any burr.

What exactly happens to the burr is still a mystery to me, whether it comes off or whether it's just reduced and aligned? The only real difference between a burr and an edge that I can find a definitive answer to is that a burr is “J” shaped and an edge is straight.

Also, most of my blades are between a Rockwell 56-58, which is just a personal preference for the types of knives I like to make.

It's been an interesting discussion,... but I have to get back to work. :)
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I get one of those awful burrs that will never let go on my SOG mini autoclip in BG-42. Great steel but it really loves to hang onto a bur and sort of turns into very flexible foil unless I use nagura on waterstones that tends to dissintigrate it.

Was taking pics of different stages of sharpening with my stereo-scope awhile back and took a pic of the burr that was curled over onto the top side.

Managed to luck out and get a section where the burr was beginning to fall off (and a tuft of paper towel from drying it.) Must have ground the edge almost through to the other side of the burr so there wasn't much left holding it on.



Looks sort of bizarre!
 
So, is it fractured or abraded behind the large burr,... or both? Is there an even smaller burr at the remaining edge?

Is the leading edge "J" shaped but so small it wears off, or a super fine jagged angled fracture?

It's very bizarre!

How's anyone going to get any sleep? ha ha
 
Excellent photo, yuzuha .... certainly illustrates how persistant that burr is. How is edge retention on that blade when you get it sharpened cleanly?
 
Actually, the reverse side was ground to the point that it wore through the base of the "j" curl so there just wasn't much left of it to hang on anymore. Usually at this point, I'd flip the knife burr side down and drag it longitudinally over the stone, which leaves most of the burr as a little pencil line on the stone, and then proceed to hone that side.

Edge retention is fine, but then I don't do a lot of heavy cutting so I have no objective measure.
 
You can sure see the diffraction grading, "colors" and how the scrathes play with the light in that photo,... but that's off topic. :)
 
The leading edge must be either fractured, abraded,... or both. If it's abraded, then there must be some degree of burr, "J" curl, trail, and texture from the grit, no matter how small. If it's fractured, it must be jagged, toothy and more opened, no matter how small.

I think this must be true until you've reach the limit of the grain and of the material itself,... either way. :)
 
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