[AwP]

The main difference between a "sander" and a "grinder" is that the grinder is sealed up so the grit can't get into the bearings and motor while with the sander (expecting only wood dust) doesn't seal it out. Since people can make knives with sandpaper and files, there really isn't a minimum, anything can make it go quicker then nothing. For one concidered "good", you'd want a 2" x 72". I use a little delta 1" x 42" sander and while I wouldn't mind having better, it does what I need it to, at least so far.