Sharpening-----New Tools

It doesn't matter if we use teflon because before it kills us off there are microwaves, preservatives, aluminium, sit coms, radiation, global warming, and oh yes, cut open an American born after 1982 and they are 95 percent zinc...with only a chocolate covering....


munk
 
Perhaps the most insidious danger is from nonstick cookware, such as Teflon or Silverstone. When overheated, these products emit fumes that can kill your bird quickly — without harming humans or other mammals. You can't smell or see the gases, so the only way to protect your bird from injury is to keep your feathered friend out of the kitchen when you're using such cookware or when setting your oven's self-cleaning feature
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This is from Dummies.com as in "cooking for dummies, photography for dummies etc etc etc etc..." so not the most reliable source. I didn't have time to search the science journal articles (if there are any which I doubt).

Munk's right though--plenty of other stuff to get you first:)
 
You know MauiRob, you're doing nothing to abate my already extensive collection of fears...


munk
 
Originally posted by munk
...cut open an American born after 1982 and they are 95 percent zinc...with only a chocolate covering....
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At least you'll save on embalming fees. :)
 
OK MauiR,

Now we're making some sense...birds such as canaries, etc are more sensitive. Hence the old coalmine trick. Don't know if it is all birds or not...Fumes released from thermally decomposing plastics affect them earlier than mammals. Since those released from slightly decomposing teflon don't smell, humans can more easily inadvertantly release them for a long time, and many won't realize the potential problem. So nothing really special about teflon except for that lack of smell. If not over heated no problem, just like any other plastic.



So, I bet a leaky old fridge might be bad, but I know that a melting plastic pot handle on the stove would be just as bad. But that stinks to us humans...so it would be quickly stopped.

BTW, I've heard of some common plastics that crank out so much nasties when they burn that even a dog with an easy escape route can get knocked down before they know what going on...I think that was a fiberglass boat in a garage that had a well-used pet entrance. Hence the now ubiquitious use of breathing gear by firefighters.

Also,using solvents, gluing, painting, etc. near the bird is probably a bad idea!

Munk--Last I heard from people that should know, there is no valid data to suggest that aluminum has anything to do with causing Alzheimer's, if that's what you're referring to.

There is however a lot of empirical data, yet to be validated, that sit-coms cause temporary, possibly permanent brain damage:p

:)
 
The reason that you compress the leather is for two main reasons, one is to make it harder, and the second is to make it flatter (and making it harder tends to make it stay flatter). It also reveals any possible problems with irregular grades or whatever.

The end goal is to have the surface as close to optically flat as possible, to provide the most even honing surface possible for the very high grit polishing compounds like CrO (0.5 micron). This is really only an advantage when you are sharpening blades with crisp flat ground edges, and wanting to achieve levels of polish far beyond simply being able to slice a piece of paper.

-Cliff
 
Originally posted by firkin
There is however a lot of empirical data, yet to be validated, that sit-coms cause temporary, possibly permanent brain damage
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...so you're saying that neurotic behavior is contagious? :eek:
 
The end goal is to have the surface as close to optically flat as possible, to provide the most even honing surface possible for the very high grit polishing compounds like CrO (0.5 micron). This is really only an advantage when you are sharpening blades with crisp flat ground edges, and wanting to achieve levels of polish far beyond simply being able to slice a piece of paper.
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I'm beginning to think that there are levels of sharpness I've never even come close to with my rudimentary skills. But I wonder, with these super sharp edges, how durable is the edge? If you do a superb job sharpening an edge to extreme sharpness, does it last longer than a so-so sharpening? Or is it just a matter of doing a better job just for the sake of it?

Thanks for any clarification:)
 
The sharper you get the edge (at a given geometry), the more durable it will be, so not only will it cut better it will degrade slower. The slower blunting is due to the greater inherent durablity, plus the fact that the effort of cutting is reduced and your control is increased.

As an example, I recently did some chopping with a some low end "machetes" (45-50 RC). Before the chopping they were at hair shaving sharp, meaning they could do a smooth push cut. After between 50 - 250 chops into seasoned scrap (different blades cut the same wood with different numbers of chops), the blades would still all easily pop the heads of off individual blades of grass.

The myth about sharp edges being weak is probably due to the fact that the sharpest blades (razors), have a very fine geometry, which would easily buckle in utility use and people are confusing the effect of the geometry with the sharpness. The weakness of a straight razor is just a geometry issue, and has nothing to do with the edge finish (grit used) and alignment, which both define sharpness.

All of this being said, the performance gain from an edge which will catch on your nail, and one that will cut a falling hair, is only a matter of a few percent on a cutting task as large such as chopping through a large piece of wood. Thus, I would simply recommend that you sharpen to the edge you can achieve with comfort.

-Cliff
 
I'm not sure why you define the absence of material behind the edge of a razor a 'geometry' issue. The one point; a sharp edge is a sharp edge, whether on the bow of a battle ship or a razor, I think I got. But the convex edge, ( say that right? curved) as opposed to a straight edge, is supposed to last longer. Maybe I misunderstood that too. Maybe the convex edge makes the knife stronger, not the edge.

Where have I gone adrift, Cliff?
 
Thank you Cliff. This sounds like one is trying to turn the leather/abrasive combination into a flatstone! (of a superfine grit otherwise unattainable) Presumably the leather must be mounted on a very flat surface for the effect to be fully realized? Does the residual "give" of the leather reduce the flatness needed as opposed to using a slurry of fine abrasive on a harder surface? (granted the slurry on a nonabsorbant surface would be messier and use more abrasive)
How hard must the blade be to have such sharpness last during use long enough that it is worth attaining?


I'm beginning to think that there are levels of sharpness I've never even come close to with my rudimentary skills.
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I know that's true for me! I've seen footage of a sushi chef holding a chunk of daikon radish darn near the size of a presto log against a large yanagi type knife while slowly turning the radish to produce a paper-like continuous sheet several feet long. Like a peeler log in a veneer mill. That is sharp!

As for Pen's question about "contagious neurotic behavior" prompted by my tongue-in-cheek comment RE sit-coms...ever seen footage of the Beatles' first visit to the US? Or more darkly, what better description of an escalating riot? (neglecting medical preciseness of terms like psychoneuropathy, etc employed by doctors, psychologists...)
 
Originally posted by firkin .....sounds like one is trying to turn the leather/abrasive combination into a flatstone
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Why not just use a good length of hardwood?
Maybe a large diameter dowel?
 
Munk, edge geometry (edge angle and thickness) and sharpness (edge finish : grit used and alignment) both influence cutting ability, however they do so in two very different ways. The sharpness of the edge directly controls how much pressure is created by a given force you apply to the knife. The visible geometry or shape of the edge controls how much wedging action is induced as the blade pushes the material apart. Thus from a very basic standpoint they are vastly different aspects.

Now if you want to get really picky, the sharpness described in the above is also just a geometrical issue. Thus you could talk about the macroscopic geometry of the edge profile (angle / thickness) [which I called geometry in the above] and the microscopic properties (grit finish and alignment) [which I called sharpness]. However from a common sense perspective, it does not make a lot of sense to go this route.

As for convex grinds vs flat grinds, at a given cutting ability, a convex profile will have greater durablity in regards to inclusions, while the flat ground edge will have greater resistance to gross rolling (a large part of the edge gets dented). This is why skilled users often prefer convex profiles as they are not concerned about gross rolling as that is mainly a technique problem as it comes from lateral impacts, however no one can avoid inclusions unless you have x-ray vision. It is simply a tradeoff of strength in one area for another.

There are complications to this of course, mainly drag issues and there are other aspects of blade performance effected, such as : convex profiles are much more durable in regards to lateral impacts, and have a much higher flexibility, however at the same time they have a much lower strength/mass ratio than a flat profile.

Firkin, yes that is it exactly. The finest stone (8000 grit waterstone) is many times more coarse than CrO. Thus if you work very hard to get a crisp flat edge you probably don't want to convex it to a large degree at the last stage on soft leather. Yes, the backing is usually rigid hardwood. Concerning dowel use, yes, you can apply the CrO right to a dowel and use it. Leather is usually preferred mainly as it is faster and more consistent as it will take the abrasive better. Plus it is more shape stable enviroment wise.

In regards to the steel, the higher the RC, the better for higher finishes, which is why Japanese have such high sharpness standards as their edges are 64 +RC. This is of course for cutting vegetables and such, not a lot of red meat in their diet so no heavy beef bones. On the softer steels the edges tend to roll quickly when cutting hard materials, however on soft materials like rope and such, they can last quite awhile so you can benefit from a high polish to various degrees. Experimentation is key.

Of course there is a lot of cutting which prefers a more coarse edge, still very sharp (alignment is high), but not highly polished. Ref :

http://www.bladeforums.com/forums/showthread.php?s=&threadid=209166

The activity on this forum is mental, as I was writing this message I had to keep editing it to reply to the other posts coming in.

-Cliff
 
ddean, maybe the leather doesn't acquire and retain dents as easily? It seems to me also, that the more resilient the surface is, the less it needs to be lapped/maintained to a regularity commensurate with the very fine grit.


Munk, I think your question depends upon where one thinks the edge ends and the bevel/grind(or rest of knife) begins. On a practical basis, I would consider that to vary depending upon the knife, the task, and what is considered or accepted to be normal wear/sharpening.
 
Originally posted by firkin .... flatstone! (of a superfine grit otherwise unattainable)
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I recall, many years ago......
Wow......many, many years ago..........

When I was in college working on something I don't remember,
I needed a drop of oil.

Now, I was sitting in a laboratory room where transparently thin
tissue sections were cut using a device called a microtome.
We're talking thicknesses down to a couple of cells using a
comparatively gigantic blade.

The rectangular blade was about 5" long, 2" wide, and 1/4" thick.
It was a sabre grind from almost the spine to the cutting edge.
Now that I think of it, reminds me a lot of a khuk.
Sharpening was done on a little machine that clamped onto the
spine of the blade and alternately rubbed both sides against
a glass plate containing a very light/fine oil-grit slurry.
Pretty neat device to watch in action.

You see it coming don't you.

I turned off the machine (I'm not a --complete-- idiot),
opened the cover and carefully reached under the blade to
touch the tip of my finger into the oil. Drop of oil
in hand I close the cover, turn the machine back on,
and return to my project.

:eek: Whatever the project was, the blood I suddenly found dripping
off my fingers probably didn't help. I had not felt the blade
slice off the top of one of my knuckles. Never did hurt.
 
Originally posted by Cliff Stamp .....Leather is usually preferred ..... as it will take the abrasive better. Plus it is more shape stable enviroment wise.
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I get it.
Do you know of any synthetics that might work as well as leather in these regards?
(I'm guessing no, or it would have been mentioned.)
 
No, but you can use just about anything to load the compound. Cordura seems obvious, though I never tried it, there are lots of grades.

-Cliff
 
ddean,

from Cliff:

No, but you can use just about anything to load the compound.
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Not very long lasting, or shape stable, but works for khuks... Cheap too!

The waxy stick of CrO can be rubbed onto the cardboard backing of paper tablets or as I prefer, very heavy watercolor paper, especially "hot-pressed" which is fairly fine grained. I'm sure that a means of clamping the stretched paper over a flat surface would enable it to be used for more precise tasks. Some artists actually soak the paper then stretch and clamp it so that it dries to a flat smooth surface as it shrinks. They can then use lots of water without permanent warping of the paper. I want to try this shrinking over a smooth surface... Worn or new fine-grit wet/dry paper loads nicely too and seems to work well, retaining some of the cutting ability of the sandpaper, but polishing also--good for touchups.

Guess I'll eventually want to get some leather though. BTW HandAmerican sells CrO in suspended in a liquid (glycerin/water or something). Seems interesting to try when the waxy sticks may not work very well to apply the abrasive.
 
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