I actually wore the sandpaper out on the blue one. It worked if there were no nicks. I replaced my blue one with the Orbitol sharpener which was over twice as much as the blue one and doesn't seem to work as well but there is less chance of cutting your fingers with it. Re-sharpened blades are only about 3/4"s as good as a new blade if you manage to get a good edge. Sometimes they just won't sharpen no matter how many turns you use.