[ny_vin18]

in the one scene in last samurie it was when the old man was sharpening a sword with a big stone or rock and it looks like it was wet with water or maybe an light oil, how does someone starpen a sword knife or dagger with a stone or big rock. is it even possible or is that just in the movies.

[armoredman]

Look at any knife shop, and you will see sharpening stones, some of which work better wetted with light oil.

[mbs357]

Yep. All knives are sharpened with stones (or something similar). I believe the oil is to keep the shavings from clogging up the grit?

[Boats]

Actually when sharpening a long blade you want a big stone or a rock. That way you can draw the entire edge across the stone face at a uniform angle whilst not wearing away the stone too quickly. What I find amusing is when the use of grinding wheels are depicted, such as in Lord Of The Rings, because even a manually driven grinder can generate enough heat to ruin the differential tempering commonly found in a sword, (harder, relatively brittle edge, and softer, springy core).

It is not as if one uses granite or limestone or something rough grained. Usually, the sharpening stone or rock is one that formed with influence of water, a finely grained type of rock called sedimentary as opposed to igneous (volcanic) or metamorphic rocks, (like diamonds). Of course, modern whetstones can be formed out of most any mineral, but the naturally occuring ones almost all began their service lives as some form of river rock.

Then again, the samurai wasn't really looking for a razor edge on his weapon as that would be too fragile for practical combat. The old school katana was convex edged, or "wedge-like" for the blade non-enthusiast. Convex edges lend themselves to sharpness, (just see a modern Bark River Knife & Tool for example) and are easy to field sharpen through some light stropping on impregnated leather, sandpaper, or other mild abrasives, and one only needs a stone to rework damage to the edge itself.

So when you see someone in a movie sharpening the edge of their sword with a rock, large or small, they are doing it right compared with how badly it could be depicted.

[Valkman]

There are Japanese water stones that you can buy along with traditional oil stones. I use diamond stones and lately just a grinder belt and stropping to sharpen.