How Sharp is Sharp Enough?

[goodeyesniper]

quick question, sort of related. Is convex sharpening ALWAYS done in an edge trailing motion? I've always sharpened edge forward, but have never convexed. I recently purchased a nice, discontinued Spyderco here on BF, and was pleased to find it had a very nicely convexed edge. At first I even thought it was kind of dull just by "thumbing" the edge, but it push cut through fine materials much better than knives I sharpen usually. I think I usually stop at a toothier edge on mine, most likely, which makes them feel sharper just thumbing.

So, I'd like to maintain this edge as convex, but I think I'll practice on some cheaper and/or replaceable knives first. I always pictured it as sharpening edge forward on sandpaper/mousepad, but the first few videos I watched all did the opposite. Obviously the final stropping is edge trailing. Guess I'll have to finally get a strop too...

 

[Gautier]

Convex edges can be maintained with an edge forward motion, on a stone. The technique is basically the same as with a V bevel except that you make a sort of "scooping" motion as well. That is, starting with the spine at the angle you want the cutting edge, and then, as you abrade the edge, lowering it to keep the curvature.

This is why freehanding results in a slightly convexed edge, no matter how much you try to maintain an angle. Your fine motor skills, and small muscles aren't strong enough to hold a rigid angle, and as your larger muscle groups take over doing the work to move the blade, your smaller muscles relax, causing the spine to lower slightly.


Gautier

 

[goodeyesniper]

Okay, yeah. That's how some of mine are that I did freehand. But for the sandpaper/mousepad to work does it have to be edge trailing? The more I think about it, the more this seems to be the case.

 

[Obsessed with Edges]

Okay, yeah. That's how some of mine are that I did freehand. But for the sandpaper/mousepad to work does it have to be edge trailing? The more I think about it, the more this seems to be the case.

Chances are, if you used an edge-leading stroke on sandpaper/mousepad, you're going to slice right through the paper (and maybe the pad too). Also, because of that soft backing, the edge is more likely to be rounded over, even if you manage to avoid cutting the paper. The natural tendency in an edge-leading stroke is for the edge to 'dig into' the sharpening media. With a soft backing, that's going to be difficult to control.

With an edge-trailing stroke, the natural tendency is for the blade edge to tilt away from the sharpening media, so the pressure at the very edge will be light (as it should be). Light pressure with an edge-trailing motion also helps to ensure that the sharpening media (the sandpaper) won't 'wrap around' the edge and round it off. Same as with stropping on leather.