The Rule of 3 – How to Sharpen
Among the fundamental skills necessary for good woodworking, I’d put knowing how to sharpen your edge tools at the top of the list. Even if you consider yourself a power-tool woodworker, I’ll bet you have at least a chisel (or two) and a block plane in your kit that need sharpening from time to time.
There are many different ways to sharpen: waterstones, sandpaper, mechanical solutions, oilstones and more. Now I’m not about to stick my head in the lion’s jaw and recommend one system over another (and I’m certainly not going to tell you whether or not to use a jig).
No matter what media you use to sharpen, there are but three operations: grind, hone, polish. (And most of the time, you can skip the first one.)
Grinding is done with a rough grit: #40 or #80 grit on a power grinder, #40-grit sandpaper on glass, a coarse diamond stone, a hand-cranked grinder, an #80-grit waterstone. But you don’t grind every time you sharpen – do this only when you need to fix a damaged edge, shrink a secondary bevel that’s become too large, or change the shape of an edge.
Unless you let your tools go for too long between sharpenings – or you damage a blade – honing is where you’ll start sharpening nine times out of 10. Honing simply erases the existing dull edge and cuts a new one. Just run the blade on the rock until you turn a burr on the backside. That burr means you’ve created a zero-radius intersection of two points – also known as a sharp edge. In fact, that’s as sharp as you can get it.
Everything above honing – from a #4,000-grit waterstone to the miniscule particles in a honing compound to a workaday hard or translucent Arkansas stone to a #30,000-grit Japanese waterstone – is polishing.
No matter how high you go, all you’re doing is progressing up the scale to a higher polish on the blade – that is, with each higher subsequent grit, you’re erasing the scratches from the previous grit (and creating new, tinier scratches).
This doesn’t make the blade any sharper – you (ideally) achieved a zero radius while honing. But polishing does make your newly sharp tool a lot more durable. Smaller and shallower scratches mean a less friable edge.