As far as I know, you should never have to sharpen the blades. The paper is abrasive enough to sharpen the blade as it works. In my experience, cutters usually need adjusting every three to five years or so, and this takes care of most cutting problems. Cutting heavy materials (linoleum or heavy boards) will eventually move the blade out of alignment and give the overall effect of "cutting curves" in your paper. Find out how to adjust your blade, and I bet it will cut like a dream! Hope this helps.