Read the other installments in the “Sharpen This” series via this link.
One of the misguided mantras in sharpening is this: Polish the edge until you remove all the scratches left from the previous grit. Then move to the next finer stone and remove all the scratches left by the earlier grit.
This ridiculousness is why it can take beginning sharpeners 30 minutes to sharpen a chisel.
Polishing doesn’t make the edge sharper (see this), it makes the edge more durable. So having a few errant scratches remaining on your edge means you might have to sharpen a little sooner than if you had achieved a perfect scratch-free edge.
Sharpening priests and priestesses will counter my statement with: Tiny scratches in the edge will leave tiny scratches on the work when using a smooth plane.
To which, I’ll counter: Yes, but sandpaper. (See this entry for a discussion of the traditional way to prepare surfaces for finishing.)
Sanity on Scratches
When you polish an edge, a few errant scratches are fine. When I sharpen on a polishing stone, here are the steps:
- Rub the bevel on the stone for about 10-12 strokes.
- Observe the bevel; if there are scratches, return to step 1.
- If there are still scratches after three visits to a stone, I move up to the next grit (or get back to work if that’s my final grit).
Sometimes I manage to remove all the scratches from an edge. Sometimes I don’t. Regardless, sharpening a tool never takes longer than one song on the radio.
One of the ways to improve your polishing has nothing to do with the brand of stones or your skill. It’s cleanliness.
In my experience, the primary cause of scratches that are difficult to polish out is stray grit on your sharpening stones. If you get big rocks on your small-rock stones, the big rocks will scratch the edge. These big rocks can be loose abrasive on the stone or even get embedded in a soft stone.
So keep your stones clean. If a stone is giving you trouble, put some lubricant on it and wipe it off with your hand. That removes loose grit. If grit has become embedded in the stone, flatten the stone and clean it off. That fixes almost every problem except for a stone that was poorly made and has coarse grit embedded throughout (yes, this happens).
— Christopher Schwarz
P.S. One more entry and then we get to sharpen things!