I'll go into a little more depth on the convex edges I do. Nothing new, here. Folks have been doing this for as long as knives have been getting dull. Some of this post was lifted from one I did in another thread.
Any edge can get shaving sharp. A 90Deg edge can be sharpened to pop hairs... but will it cut efficiently?... hell no.
It's what comes after the edge that counts. The shoulder and bevels dictate how a blade will perform.
Convex's claim to fame is that it combines less surface friction (next to hollow ground) with the most mass behind the cutting edge, for strength. Most of the time (especially woodcraft), the material you are cutting is only making contact with a small point on the arch of the convex bevel. The more surface area that comes in contact with the material, the higher the chance of binding. Like aero-dynamics in a car, you want to have the least amount of resistance that you can. Simply convexing the edge won't give you superior results either. A steep convex will try to force the material apart, abruptly. There is too much shoulder behind the edge. Sometimes, jumping on a mousepad before you've established good convex geometry, will get poor results. You will still be able to shave and for the most part, slice paper… but it won't be efficient in the field.
A flat "zero" grind or "Scandi" will carve like nobody's business but if you are going to use it for battoning or chopping, you may find it's not strong enough. The steep 30+deg angle of the typical Scandi, also makes it less efficient at slicing. That is a combined angle, btw. Moras are the thinnest at 12.5degs per side = 25deg edge. Most scandis are 15-20degs per side.
A well executed V-grind will work nicely for many applications but IMO, most have too much shoulder, still.
My edges are a mix of three geometries... Flat, Convex and V-grind.
-I forge as close to flat as possible leaving about 3/64" for the heat treat.
-Then I grind the edge to a very shallow convex... actually TOO THIN to retain sharpness in use.
-My final process is putting a micro-bevel on with a stone (up to 8000grt) then I do a final strop with wet newspaper laid across the stone.
I also use stones to put a full convex on a blade. Its time consuming for large choppers but fairly easy for smaller knives.
I lay the blade down flat to the stone (approximately 600-1000grit) with the edge toward me. I push away from my body the same way you would use a strop. At no time do I ever slide the blade “edge first” down the stone. Toward the end of my stroke I apply a little more pressure at the edge with my fingers. This eventually removes stock to the point where the spine begins to lift… now you’re putting a convex bevel on it. I alternate 10 strokes per side until a burr forms. I move to a finer stone (4000 grit) and repeat the process. After a burr has been establish with the 4000 grit, I raise the spine to about 10-12degrees and strop the burr off. At this point I switch to an even finer stone (8000grit) and strop some more. I’m very light with these strokes and only use the weight of the knife. I glide the edge (under its own weight) down the corner of a piece of wood to remove the burr. Then I lay a piece of wet newsprint across the stone and strop one last time.
Here are some pics of my set-up…. I’ve been meaning to put together a full thread on sharpening. For now this will give you an idea…
Rick
