Auriou, Liogier, and Gramercy are hand cut rasps. Corradi and Nicholson are machine cut. Corradi claims that their teeth pattern and the consistency of the machine stitching makes for a rasp that makes a cleaner cut. Since I haven't used Corradi, I can't verify if that's true. Part of that is marketing. Corradi rasps do get consistently good reviews.
Rasps can be sharpened similar to files. Boggs Tool in California can do that. Or you can soak them in vinegar for an hour or so. The best way to keep rasps sharp is to consistently keep them clean and also to protect the teeth in storage. Throwing a bunch of rasps in the same drawer with them all touching each other (like I've seen at well-known woodworking store chains) is a no-no. Either dedicate a location for each individual rasp, wrap them with paper or cloth, put them in a sheath, or a tool roll. Even though rasps are hardened steel, the tips of the teeth are vulnerable to getting bent or dulled if they bang against other hard metal surfaces.
Rasps can be sharpened similar to files. Boggs Tool in California can do that. Or you can soak them in vinegar for an hour or so. The best way to keep rasps sharp is to consistently keep them clean and also to protect the teeth in storage. Throwing a bunch of rasps in the same drawer with them all touching each other (like I've seen at well-known woodworking store chains) is a no-no. Either dedicate a location for each individual rasp, wrap them with paper or cloth, put them in a sheath, or a tool roll. Even though rasps are hardened steel, the tips of the teeth are vulnerable to getting bent or dulled if they bang against other hard metal surfaces.
Still Learning,
Allan Hill
Allan Hill