How to Sharpen With Sandpaper

Keep knives honed to a fine edge with sandpaper.

Sandpaper glued to a smooth base will sharpen knives, chisels, scissors or planes like a traditional sharpening stone. However, it's cheaper, readily available at hardware or auto-parts stores and easier to maintain. When sandpaper becomes worn, you can discard it and glue on another piece, rather than needing the tools to dress a stone. By choosing different grits from 80 to 1,000, you can smooth out obvious roughness and work up to a mirror-like, razor-sharp edge on a blade.

Things You'll Need

• 1 piece of smooth wood or particle board, 4 x 10 inches, 1/2-inch thick, or glass, 4 x 10 inches, 3/8-inch thick
• Glue or spray adhesive
• 80-grit sandpaper
• 120-grit sandpaper
• 320-grit sandpaper
• 600-grit sandpaper
• 1,000-grit sandpaper

Instructions

1. Cut or buy a piece of smooth wood, particle board or glass at least 4 x 10 inches. Choose wood that's 1/2-inch thick or glass that's 3/8-inch thick. If you have a piece that's slightly larger, use it the size it is. Your goal is to create a perfectly smooth, flat base for the sandpaper, but the size isn't crucial.

2. Cut a piece of 320-grit sandpaper the same size as the board or glass and glue it to one side with spray adhesive. Do the same with a piece of 600-grit sandpaper on the other side.

3. Lay a piece of 120-grit sandpaper on top of the 320-grit sandpaper for initial sharpening. The friction with the glued sandpaper beneath it will keep it still, but if you want, you can make another sanding block by gluing 80-grit sandpaper on one side and 120-grit sandpaper on the other.

4. Examine the blade you want to sharpen to see if it's like a chisel blade (flat on one side, slanted on the other) or a knife blade (slanted on both sides). If it's a chisel blade, be careful when sharpening not to accidentally round the flat side.

5. Smooth the flat side of a chisel blade by laying it perfectly flat against the sandpaper and rubbing it from side to side and in small circles. Make sure to keep it flat and press slightly behind the cutting edge becasue you don't want to round the surface. When the surface is as flat as you can get it, finish by rubbing it on the 320-grit sandpaper. If the 120-grit sandpaper seems too fine to remove pitting, grind marks or nicks, begin with 80-grit instead.

6. Sharpen the beveled edge of a chisel blade, or both sides of a knife blade, by starting with 120-grit sandpaper again, or 80-grit if the blade is very nicked or rough. Lay the blade flat on the sandpaper, then slowly angle it upward until the slanted edge lies against the sandpaper. Hold the blade at that angle and slide it from side to side so it won't cut into the sandpaper. When it's as sharp as the 120-grit paper will make it, remove the 120-grit paper and switch to 320-grit, then finish with 1,000-grit paper. If the blade is curved, rock it slightly as you slide it sideways so the angled edge is always touching the sandpaper.

Tips & Warnings

• If your blade is already almost sharp, start with 320-grit sandpaper. Start with 600-grit if the blade is barely dull and only needs a touch-up sharpening. For an even finer edge, finish with 1,000-grit sandpaper.

• If you need to sharpen a concave blade, glue the sandpaper to a dowel that's about the same size as the inner curve of the blade.

• A glass base is ideal because it's hard and smooth, but be careful of the sharp edges. Bind them with tape to protect your hands.

References

• "American Woodworker; Scary Sharp"; Mike Dunbar; June 1998
• "Taunton's Complete Illustrated Guide to Sharpening"; Thomas Lie-Nielsen; 2004
• "Woodcarving"; Everett Ellenwood; 2009