Sharpening: Here's What I See
I’m fairly well convinced that my ears are different than yours. The music I like isn’t going to sound the same to you. It’s almost impossible for me to share with another person what the Heartless Bastards sounds like to me. Language is too imprecise.
Same goes with the eyes (and tastebuds). How you experience a Paul Klee or a Hebrew National is impossible to share with me.
The problem is that our senses are tied to our big, dumb brains, which process and filter the waves of information our organs receive.
And so it makes me crazy to explain how to sharpen to people because it involves so many senses (except taste I think) that are processed. And there is so much information that comes in through our eyes, fingers and ears that beginners cannot focus on what is important.
So here is what I see when I sharpen a plane iron. I’m going to show what it looks like on the unbeveled side, which I call the “face” and others call the “back.”
Above is what the face of a smoothing plane iron looks like when it is fresh from the wrapper. The vertical scratches are deep and are left behind by the manufacturing process. These have to be removed. So I begin by abrading the tool on my #1,000-grit waterstone.
After a short time on the #1,000-grit stone the metal gets a scratch pattern that looks like this. I move the iron back and forth diagonally on the stone and examine it every couple minutes. I’m looking for where the deep vertical scratches go all the way to the end of the iron. That’s where the metal is weakest and the edge will begin to break down. The arrows point to where I see problem scratches. When these scratches disappear at the end of the iron, I can move on to the next grit , #4,000 grit.
Usually #4,000-grit stones start to give me a good polish. And so the #1,000-mesh pattern is generally replaced by more of a polish. Some #4,000-grit stones don’t do much polishing, but most do. Try working the iron in one direction , this brings up the polish faster.
If I can see the deep vertical scratches, I might need to drop back to the #1,000 grit. In the drawing above you can see some #1,000-grit scratches and one deep manufacturing scratch at the right that are problems. Usually I’ll drop back to the #1,000-grit stone here for a few minutes to get that deep scratch out.
I’ll also start to see faint horizontal scratches left behind by the #4,000-grit stone. When the #1,000-grit scratches and manufacturing scratches are gone, move to your next stone. For me, that’s the #8,000-grit waterstone.
This stone should bring up a nice mirror-like polish. You might have some horizontal scratches from this stone, but those generally aren’t a problem. Look for any #1,000-grit diagonal scratches (as shown with an arrow above). Keep working until all the vertical and diagonal scratch marks are polished away right at the cutting edge. Don’t worry about the scratches that don’t make it to the edge.
I’m sure all this looks different to other experienced sharpeners, but these crude pencil drawings are about as well as I can explain it without coming to your house.
– Christopher Schwarz