Thread: Blade size and sharpness?

A question for the honemeisters out there:
All other physical properties being equal (material, spine width, blade shape) would a wider blade take a keener edge than a narrower one? Looking at it from the tip, the edge forms one point of a triangle; the farther away that point is from the base of the triangle (the spine), the more acute the angle at which the hone contacts the edge will be. (The attachment is a rough attempt to show this) This would seem to indicate the ability to put a 'sharper' edge on a wider blade. Any real-world experience with this? Or is the difference in angle too little to have any effect?

The difference would be in how fine a stone you intend to finish on. Most cutting edges seem to max out at around .3 microns in width at the very edge, so the closer you can get to that figure and with the least variation down the length of the blade, the sharper the edge would be.

An extremely fine stone would render those two edges equal and the more obtuse one would hold it's edge a bit longer because it wouldn't be as fragile.

But a 5/8 with a 1/4 inch back would look kinda silly.

Ah - that's what I was missing - I didn't consider that there's a practical limit to how thin the very edge will actually get. I've been honing knives all my life but haven't ever given any thought to what's really happening until I started with straights.

Thanks Russel!

You can get equal sharpness with any razor I don't care if its a 2/8s or a huge monster wedge.

Yep, on the microscopic scale the steel just doesn't hold it's shape and edge past .3 microns or so.

There is a document of sharpening experiments by a guy named Verhoeven in the archives, they examine a few blades and find that none get much thinner than about .4 microns, but with some of the new super steels and advanced heat treat/tempering regimes I wouldn't be surprised if that number could go down a bit.

One of the most controversial topics among bladesmiths is edge geometry. You're now in it with both feet! My recommendation is you get a Starrett angle gauge and check out a bunch of blades to see which shaves best for you. In knifemaking, we use finer edges for cutting meat and soft soft like whiskers and the blades are often, but not always, hollow ground like a razor. If you're going to be cutting something harder like 2x4s or saplings or coconuts, you don't want a hollow ground as it will crumple. Same thing when a straight razor hits a bone, belt buckle, or other hard objects. There's not enough behind the edge to support the shock. My personal opinion is that razors have evolved to the angles they have because they work for customers and shave well. It's a fun topic to talk about.

Originally Posted by Howard

One of the most controversial topics among bladesmiths is edge geometry. You're now in it with both feet! My recommendation is you get a Starrett angle gauge and check out a bunch of blades to see which shaves best for you. In knifemaking, we use finer edges for cutting meat and soft soft like whiskers and the blades are often, but not always, hollow ground like a razor. If you're going to be cutting something harder like 2x4s or saplings or coconuts, you don't want a hollow ground as it will crumple. Same thing when a straight razor hits a bone, belt buckle, or other hard objects. There's not enough behind the edge to support the shock. My personal opinion is that razors have evolved to the angles they have because they work for customers and shave well. It's a fun topic to talk about.

Oh grrrreat - another thing I need to buy! Thanks for the input, Howard. It would be interesting to compare angles on the razors I get the smoothest shave from vs. the ones I don't.