So how do you sharpen a rolled edge?

mps, have you considered the standing burr and its performance with the convex edge? It's possible the burr grips the material to be sliced, and the convexity then shoulders it out of the way. It's also possible that the process that develops the convex edge also develops a different, more effective burr (larger/smaller/wider/thinner?). I suspect significantly wider at the base, with more shoulder to grow from than would be possible from a straight bevel.

madpoet, thanks. Perhaps some of this could properly be included in the Knowledge Base; I get the impression the topic recurrs constantly.

I never considered the simplicity of the strop method madpoet outlined. "Everyone knows" stropping is for razors, not for knives that need strength as well as sharpness, and for that one uses a stone and grinds beautiful, sharp bevels. I also never considered using the same file stroke on my expensive knives that I use on my hatchet; hey, "everyone knows" they're different things, right?

I believe I'll combine this advice with P.J.'s and start with some cheap blades and see where it leads me.
 
I don't have any convex edged knives yet, but am do to get some very soon. I will be trying these methods. Of course, my H.I. khukuries are convex, but I steel them with the tools that they came with.

I noticed at the Las Vegas knife show, that there was a knife maker that had small polished convex knives. The whole side of the knife was convex, not just the edge. Looked very interesting. Looked wierd to me.
 
A small, totally-convex blade...hmmm could that be one the the Sean Perkins knives? His are small ~4" or ~6", with 2" blades, and the blade is has one side flat, and the other a convex grind all the way to the edge.
Aaron

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aaronm@cs.brandeis.edu
I like my women like I like my knives: strong, sharp, well-formed and pattern-welded!
 
For a low cost knife with a full convex blade try an Opinel.
Btw they are a great value, and have a lock that cannot fail.
 
Most guys punding steel will use a "convex" grind which is "convex" from the spine to the edge. Some of the "hammer" people will grind flat, but they are the exception rather than the rule. the theory is that this grinds provides greater strength and a thinner edge, as well as a smoother transition from initial matter separation to follow through.

The term "Hamaguriba" has been used in Japan for the past 1,000 years to describe the same grind configuration.

Mps - my guess is the difference you feel in slicing may be due to the fact that the convex grind has less "surface" contact with the material being cut. eg; cucumbers will easily stick to the side of a flat ground knife becaue of the full surace contact and moisture. In order for the cucumber to stick to the side of a convex ground knife, it would have to be thin enough to "bend" around the grind.
sal
 
I use a bench grinder with a compressed fibre board wheel to put a final rolled edge on all my using knives. Any knife supply has these wheels and the polishing compound that goes with them. Basically, you just change the angle of the blade with each swipe on the wheel. These wheels produce very little heat as long as you don't hold the blade in one area too long or press too hard on the wheel. The "convex" edge I achieve seems to stay sharp way longer than a "flat" edge (from, say, a Lansky sharpener). The polished edge becomes like a mirror. Unfortunatly, this razor edge (you have heard of "hair popping") has no grab when cutting material like rope so I rough up the back section of the knife with a stone and leave the front part smooth.

By the way, the fibre board wheel is what Microtech uses to put the final edge on each of its blades. If you don't want a convex edge just make sure the blade angle to wheel doesn't change.

Also, it is very hard to screw up using the fibre wheel. Just make sure you put masking tape on the handle incase you slip. And keep a good grip on the knife. When my blades loose their edge, I just make a few passes on the fibre wheel and they are sharp again.

jc
 
While the "convex" grind may have a very slight cutting advantage for certian applications, I doubt if I could tell the difference. And, the time and trouble for re-sharpening are not worth it to me.

Unless you have and are skilled at using an electic bench grinder with a cloth wheel w/ abrasive compounds, or sharpening by using one of the methods above, it may be much easier to use the Lansky sharpening system and a course diamond stone to put a 20 or 25 degree bevel (depending on the knife and use)on the edge.

Then, later resharpening is quick and easy with the Spyderco Sharpmaker.

I look at the cutting abiliity sort of like as with areodynamics or hydrodynamics. Friction (air or water) is your enemy.

In knives, you generally are trying to simply seperate material - flesh, rope, whatever, in whole or in part. The more the resistance, the less efficient the cut.

Certianly cutting ability is more complex than this - knife geometry, the weight and width and thickness of the blade, lubrication from the item being cut, etc, etc.

But from a more pragmatic approach, you must consider the time spent sharpening as all edges errode from use. Given that, the "rolled edge" doesnt work well for me.
 
jc,

I made my post before seeing yours.

Maybe I will have to get a grinder and the fibre board wheel.

I did have had a tanto sharpened ( at a knife show) this way and was impressed with the razor edge and mirror polish. The kind of edge that your wouldn't even feel being cut by.

How do you do field touch up resharpening? Does a round steel straighten up the edge adequately?
 
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