Rasps are not the first tools that come to mind when we think about woodworking. And yet, they are just the thing for shaping curves too tight to be cut with a spoke shave, too irregular to be routed, or where the grain is too squirrelly to be easily carved.
I’d been a woodworker for 20+ years before I came to appreciate the rasp—in part because I’d never used one that wasn’t old and dull. I was building a contemporary chair and needed a way to shape the curved area where the rungs were to flow into the legs.
None of my tools were up to the task, so I bought a couple of rasps. I was pleased by how well they worked and at the same time puzzled by how it was possible to cut so many small sharp teeth into hardened steel.
Hand stitching an Auriou rasp.
Big companies, like Nicholson, use machines, but there are still some folks who do it by hand. Among the better-known practitioners of this art is Auriou Toolworks, a French manufacturer whose process has been immortalized in the video below.
Compared to mass-produced rasps, the ones from Auriou are expensive, but when you see what goes into making them you’ll wonder how they can be sold for so little.
http://www.core77.com/posts/67277/This-Video-of-Auriou-Toolworkss-Production-Process-Makes-You-See-Wood-Rasps-in-an-Entirely-New-Light