Unequal sharpening

[jim_w]

I was sharpeing my knife last night, and it started me thinking about how edge geometry changes over time. Assuming perfect sharpening, a convex edge should simply move back towards the spine, keeping its shape. Right?

So, what if I don't remove the same amount of material from each side of the blade? I suck badly at visualization and so forth - I can't picture what's happening to the edge here. Am I making a lop-sided apple-seed shape? Or does it all work out?

 

[Jeff Clark]

If you sharpen unevenly your edge will probably move off-center a bit. The edge angles will not match. Your blade would shave better on one side than the other or whittle better on one side than the other. In the extreme, if you only sharpened one side, the edge would get extremely off-center. This would make the edge less well supported on one side than the other. If you impacted something tough like bone the edge would tend to roll over to the weak side.

 

[Cliff Stamp]

I assumed for awhile that since it is all random it would all average out, this turns out not to be the case. Most people are hand biased and will sharpen at one side higher than the other and thus you end up with uneven angles, like 15 on one side and 25 on the other. In the extremes these have problems like Jeff noted and cause a lot of problems if you try to use jigs or v-rods.

-Cliff

 

[yuzuha]

I can't picture what's happening to the edge here. Am I making a lop-sided apple-seed shape? Or does it all work out?

You'd be making a clam-shell edge, popular on some Japanese kitchen cutlery (slight angle inside, larger angle outside, tends to push away food slices and push the knife in towards the food helping make more even slices).