Sharpening questions

[Gradyw]

other then aesthetics does sharpening the edge say 15 degrees on one side and 20 degrees on the other matter?( I may be over exaggerating) or if I have a 20 degree belly and 15 degree tip as far as sharpness is concerned? When re profiling an edge most he time I get in a hurry and get tired of trying to make it perfect and just start sharpening as fast as I can. If I've been working on it for more then ten or twenty minutes I will proceed threw all my stones like this if I'm putting a mirror on my edge. I have never had any problems with my edges getting very sharp this way no matter how uneven they look. My main concern is in doing this am I actually not getting my edges as sharp as they can? Mainly just sharpening on different degrees on each side cause it's no problem to take off too much material by accident and fixing it towards the end when I start forming a burr and I know I'm getting close

 

[Petunia D. Feeble]

Yes and no.

There's a lot of things to consider. I assume you're using some sort of fixed angle system? If so, 15 on one side and 20 in another may not even be accurate. The angle listed on a Gatco or Lansky are just rough estimates. Things like blade thickness and width can affect it.

As for a difference in angle, a more obtuse angle will always have more drag and thereby not cut quite as well, but the fact that they're different makes no real difference. Chisels cut just fine and they've got angles as different as they could possibly be.

The real key is to just make sure the edge is as keen as it could possibly be. Slow down on your final stones and you should be good to go.

 

[Gradyw]

No I freehand. I normally go back and fourth real fast until I have a bur or either get really close to it. Then I slow down and my angle would more then likely at least stay consistent until I switch sides

 

[Alberta Ed]

A few degrees shouldn't make much difference in cutting effectiveness. An angle guide would help keep the bevels similar, but in real life nothing approaches perfect bevels both sides.

 

[bgentry]

Chisel ground edges work great on knives. Chisel ground edges are "0 degrees" on one side and 10, 15, 20, 25 degrees on the other.

Symmetry is good, but it obviously doesn't hurt cutting performance much to have an asymmetrical edge, as chisel ground edges can cut like crazy. Chefs and other food people say that asymmetrical edges "steer" the blade as you cut through food. I think that's the only real measurable effect.

Brian.

 

[Obsessed with Edges]

You might notice in cutting tests, such as in slicing paper, that the asymmetry might tend to bias the direction of the cut to one side or the other. The cut path will be steered away from the more obtuse side (narrower bevel) and toward the more acute side (wider bevel). So, in slicing paper, you might see the blade wants to cut in an arc through the paper. A dead-perfect symmetrical edge would self-steer more or less in a straight line through the paper, or at least freely turn either way, depending on how you steer it yourself (cutting circles or S-curves, for example). In ordinary cutting tasks, you likely may not care about a little directional bias anyway, so long as the apex is crisp.

If the asymmetry were in a large, heavy chopping blade (axe, etc.), it could get a bit unwieldy and even dangerous, as the spine of the blade will want to lurch violently to the narrower-bevelled (more obtuse) side on each strike, which can turn the tool off-target and towards who-knows-what (glancing strike off the edge of a log with an axe, for example).


David

 

[Gradyw]

You might notice in cutting tests, such as in slicing paper, that the asymmetry might tend to bias the direction of the cut to one side or the other. The cut path will be steered away from the more obtuse side (narrower bevel) and toward the more acute side (wider bevel). So, in slicing paper, you might see the blade wants to cut in an arc through the paper. A dead-perfect symmetrical edge would self-steer more or less in a straight line through the paper, or at least freely turn either way, depending on how you steer it yourself (cutting circles or S-curves, for example). In ordinary cutting tasks, you likely may not care about a little directional bias anyway, so long as the apex is crisp.

If the asymmetry were in a large, heavy chopping blade (axe, etc.), it could get a bit unwieldy and even dangerous, as the spine of the blade will want to lurch violently to the narrower-bevelled (more obtuse) side on each strike, which can turn the tool off-target and towards who-knows-what (glancing strike off the edge of a log with an axe, for example).


David

Thanks. Good post.