Single Bevel/Profile Experiment

Cypress

Cypress

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Jun 22, 2009
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Ever since I was a kid, I have been mesmerized by the idea of a straight-profile blade... I'm sure there is a technical term for it, but think of a knife that has no edge bevel. The cutting edge is the same as the rest of the blade, and depending on the blade, can have an effective edge degree of less than 7 degrees. I call it "flatting".

I had kept this knife around for just such a task (and my grandfather gave it to me when I was 11). The patent on the blade was filed in 1940! I figure the old carbon steel would be best for this experiment.



Here's my grand idea: I press the full blade against my diamond stone and just go to town. I ended up losing a bit of skin off of my fingers, as the stone would pull the skin under the blade, shaving it cleanly off.



Here's an American quarter for blade width comparison:



After doing some guesswork math, the eventual angle of the blade ended up being 6.7 degrees :eek:

BUT, that's where everything went wonky. As expected, the edge developed quite the burr. In an attempt to remove the burr, I dragged the edge across a new clothes pin. Once I was satisfied that the blade had been deburred, I checked the edge with my finger. It felt EXTREMELY sharp! I looked at the blade and noticed that the area I had run my finger down was "dented". Turns out, the edge was so scary thin that my own calloused finger rolled the edge and chipped a piece off in the process.

Another problem was the belly of the edge. Flatting a knife is fine if your knife has a 100% straight edge. This knife is pretty standard, and the stone wasn't touching the edge after a certain point. The gentle tapering in the blade made it impossible to flat the knife without turning it into a modified tonto :grumpy:

I eventually gave up and put what I can only think to be a 12 degree bevel on the knife, oiled it, and put it back in my knife collection. Anybody else ever tried this?

 
Nice try!
What might be very good is to make it look like a single bevel Japanese kitchen knives.
Grab some sort of powertool and hollow out one side instead of flattening it.
That way you can do exactly what you did (put it dead flat on the stone and just grind)
and you'll get that bleeding edge honed every time.
I'm thinking dremel would do it nicely.
 
I have been working on the exact same thing with my Kershaw chill. It's a real pain in the butt, as of right now some parts of the edge are zero bevel while some parts still have part of a bevel left. Even at DMT Extra Coarse finish (roughly 120 grit IIRC) the zero bevel section manages to whittle hair! As you can see, I still haven't worked all the way into the hollow grind :eek:

Half_Flat_Chill.jpg
 
I've had similar difficulties with very acute angles but since learned that burr formation may be the problem and not a symptom. After removing the burr try sharpening again without forming a burr.

Down around 6 degrees inclusive I noticed little disks of skin floating away from my fingertips just from handling, like bpeezer said without getting close to final grits very high cutting ability
 
I did that with a manix2... Got rid of the hollow grind and put a 24 degree microbevel on it.
 
I think alot of people call this a zero grind, meaning no secondary bevel. True scandi knives have a zero grind, but are much steeper than 7 degrees. I think you will need a steel with very high hardness in order to achieve such a thin edge, but you still might experience chipping. Some people also do zero grinds on convex knives.
 
Yep, low angle grinds just don't last with the slightest abuse, for slicing light stuff they're great, not the kind of edge you want to do anything else with, they'll make you pay for it.
 
It's all about the Hrc, and those knives don't have it.
 
Take a look at straight razors. They are designed to be sharpened with the blade laying against the stone/strop. They tend to have a high hardness and a very fine grain of steel.
 
Yes but straight razors are honed at 15-17* inclusive, not 6. Even still, straight razors are very delicate edges, deforming with a thumbnail press.


-X
 
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