Convex grinds and mini-bevels

[jokrswylde]

Ok, here's the deal. I recently purchased a BRKT with a convex edge, and they strongly recommend sharpening by stropping, and not using stones. I was skeptical at first, but after seeing how the edge came alive after a few passes on the back of a notepad, I was convinced. It was truly surprising how quick and easy the edge came back.

I have a few other knives (Sebbie, Busses, for example) with convex edges that I have already sharpened by using the sharpmaker. The edges are all xtremely sharp, but I assume that I have put a micro-bevel on them, and they will not respond to stropping as they would have originally.

My question is, is there any way to reclaim the convex edge without having them reground, I find stropping is much more efficient than the sharpmaker. And I am more prone to have a leather belt outdoors than my sharpmaker. Or have I doomed myself to using the sharpmaker on these blades forever?

 

[DGG]

There is no reason you can't strop any bevel. A chisel is the best example of something that is honed/stroped without being convex ground. You can of course convex grind any knife or use a multi-bevel approach.

http://www.drsharpening.com/leatherhone.html

http://knifeart.com/geomofcutedb.html

http://forums.egullet.com/index.php?showtopic=26036

http://www.mhcable.com/~yocraft/sosak/convex.htm

http://www.bladeforums.com/forums/showthread.php?t=368828

http://knifeart.com/sharfaqbyjoe.html

 

[jokrswylde]

Thanks for the reply. I know you can strop any grind, but I was under the impression that convex grinds were made SPECIFICALLY for stropping. None of the other knives that I strop have responded the way the convex grind does. I am getting similar results from stropping the convex edge for about 2 minutes that I get with my other knives after about 15 minutes on the sharpmaker. Maybe its the steel/heat treat?

 

[HoB]

Sandpaper of various grit on a mouse pad is probably the easiest way to establish and maintain by hand a convex edge. Slackbelt belt grinder works obviously as well. Or you can roll the blade on a stone. Needs quite a bit of practice but in principle is not difficult. Cliff explained that in a recent thread. you start with the spine on the stone and pull the spine up, while dragging the knife in a stropping motion across the stone. The trick is, that you should stop always with the spine at the same hight on each stroke. That needs a lot of practice. But there is no reason why you couldn't do it forward edge leading. I find it is more difficult and in general I have come to prefer a stropping motion on fine grits anyway, but there is nothing special about stropping a convex edge. There is no magic in sharpening. What you are seeing is the excellent blade/edge geometry that BRKT knives come with. It is a full convex to ZERO edge (meaning no edgebevel) that makes for a very accute edge that is very easily maintained if you don't let it get too dull. Also I find that A2 in general takes a very nice edge very easily. It doesn't burr too badly and polishes very nicely too. It doesn't have the abrasion resistance as S30V for example either, so it takes fewer strokes to get the same result.

But on a side note: 15 min on a sharpmaker implies that your edges are not acute enough and could use some thinning out. You shouldn't need more than the 20-20-20-20 strokes on each step to get a very nice edge...maybe 40-40 on the whites if you are picky but that still doesn't add up to 15 min. Also if you start out with similarly acute edges of similar quality they should respond very similar to stropping. Even if one is a flat grind, and the other is a convex grind. The very edge (if you'd draw a tangent to the edge if you will) was on my BRKT around 12 deg. per side (just a rough estimation) the way it came. If you compare that to a knife with an edge bevel of a 20 deg. per side, you compare apples and oranges.