Friday, May 6, 2016

Rasps Part 2 - Auriou Rasps

I just finished discussing the types of rasp and differences between machine-made and hand-stitched rasps, ultimately to rationalize why I bought the high-quality Auriou rasps that I did. Now let's take a look at what I got. Hopefully I can justify why I chose to spend more for the quality tool I bought. In my defense, the baseline is "life is too short to buy crappy tools" so I ought to be able to say "they're good tools" and meet it. However, I do want to show *why* they're good tools.

So the way a rasp works is not dissimilar from how sandpaper works. When you're sanding you want remove a lot of material, so you start sanding with rougher grits like 80 or 120 grit sandpaper. Once the rough-grit has done it's job, you want to smooth out the visible sanding scratches, so you move on to sand with 120, to 180, to 220, and (possibly) beyond, each successive grit getting smoother and smoother, finer and finer.

The same principle applies to using rasps. Big, aggressive, rough, teeth take off more material but leave behind a commensurately rough surface. So you move up along rasp roughnesses along the something that is conceptually equivalent 80 to 180 to 220 grit pathway.

Let's take a quick look at a comparison picture that Auriou publishes on their website to demonstrate the varying "grades" of rasp:

If you blow it up you'll see that they grade from 1 (roughest) to 15 (finest). I bought an 11 and a 15.

The categories that are used to describe Auriou rasps are roughing, cabinet maker's, and modeler's, My 11 is a cabinet maker's and my 15 is a modeler's. I'm going to try to post pictures of what they look like and what they do to wood as they are used from here on out.
Cabinet Rasp, Grain 11
Modeler's Rasp, Grain 15
Now an attempt to show them in action. Really, I need a macro lens set up to do this right, but I'll try to get my camera to cooperate (yes, I'm aware that I could have used a macro lens to get pictures of the grain and stitching on the rasps to turn out better but they're pretty pricey and I spent all my money on rasps, lay off).

Original, no rasp

After the cabinet rasp

After the modeler's rasp
It's hard to see in the pictures, but the 11 was able to shape the curve, and the 15 smoothed it out so that only minor sanding was necessary. The irregular teeth minimized railroading, leaving barely any "machine" marks that need to be smoothed with sandpaper.

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