I use a "slightly used" blade to rough cut the covering. I keep it fairly sharp by dragging it lightly across 600 grit sandpaper frequently. But, I always use a new blade when I do the final cuts in the covering. If I have them available, I prefer razor blades. If you notice the painting segments of American Hot Rod or American Chopper, they always use razor blades. They last longer than #11 blades.

Paul