Kawakami

Everyone likes sharp swords! Everyone wants their sword even sharper! The sharper the sword, the better it cuts! Razor sharp!

...Something that so many people overlook is the fact that a blade CAN be too sharp. The key in making a sword that will last is having an edge geometry that is sharp, but not too sharp. It needs reinforcement. Sure, a razor blade can cut something soft with a lot less effort than an axe, but if you take into account that not everything that is cut is soft, that not every target will be sliced shallow, that impact will take it's toll...then you will begin to realize that you don't want a thin, fragile razor blade.

NIKU IS GOOD!

Niku is the convex shape given to the sides and edge of swords to reinforce the hardened ha. With hard metal, you have to be concerned with fragility. Wet clay will not be damaged as easily as glass. Wet clay won't cut anything, either, though. Glass will. When cutting is important, then you'd pick the glass over the wet clay. You'd just reinforce the glass, right? If you wanted it to last, at least.

What I'm getting at is this.

Super thin and sharp will cut soft targets beautifully if technique is on. If technique is off, or the target is hard, though, you will damage your edge. A chipped, dulled edge will not cut as well. To keep that from happening, keep the edge reinforced. Keep the meat on the blade, find where it is just sharp enough to cut well, and leave it at that.

Kawakami