Sharpening a knife with this sandpaper method will give you a sharp edge on your knife. The good news is that learning how to sharpen a knife doesn’t mean you have to keep the angle perfect the whole time. For sandpaper, I recommend the motorized wet/dry type. You can buy them in a variety of packs which will be suitable for sharpening quite well.
Step 1: Preparation
Cut your wood scrap 3- to 4-inches wide, and as long as your mousepad. Cut the mousepad to fit the width of the wood and glue the fabric side (the surface the mouse moves on) to the wood. You can do this on both sides of the wood so it doesn’t slide around on your table. The rubber side on the outside helps keep the sandpaper in place. I used a simple spray adhesive and got good results.
Step 2: Marker
As with the sharpening stone method, I recommend using a permanent marker to mark the edge bevel of your knife. Paint the entire edge bevel so you can easily see where the paper is removing material. This will help you determine the correct angle for the next step.
Step 3: Find the angle
The angle is slightly less important with the convex edge because the edge has a curve due to the flex in the mousepad base. Even if you’re off by a few degrees, padding will cover your mistakes. Place a piece of 600-grit paper on the block and hold it with your fingertips underneath. Hold the knife facing you and at a 15 to 20 degree angle from the paper. Starting with the tip at the bottom corner, push the knife away from you while sweeping to the opposite top corner of the block. Now look at your marker to see where you are removing material. The same combination applies here that I described in the sharpening stone method.
Step 4: Raise a Burr
As with the stone method, once you find your angle, you make passes on one side until you raise a burr, then switch sides and raise a hole again. Do not start with a grit less than 320 unless the blade has deep chips or rolls. The lower grits will remove material quite quickly and you can mess up your blade if you’re not careful. Also, you don’t need a lot of pressure for this method. Too much will cause too much distortion of the pad and make your curve too steep. A light touch works best. Remember to be careful with your fingers holding the paper.
Step 5: Refine
Once you have a burr raised on both sides, you can change the grit and start refining your edge. Take the next grit and make ten passes on each side (or until you have removed the scratches from the previous grit), then go up and do the same until you reach your final grit, then make ten strokes on each side and decrease the number described in the stone method. If you go up to 2000 grit, you’ll start to get a mirror-polished finish on your blade. If you are diligent about maintaining your angle and hitting the apex, you will have a very sharp knife by the time you reach 2000+ grit. You can get a grit of 6000 and up, which will really polish and refine your edges, and I can easily get an edge that will make hair sparkle with this method. Read more: How to cut green onions
Note that using this method always requires the tip to be behind the spine. You can’t pass where the edge goes on the paper. It might work on a rock, but not here. Also, the paper can be taped to the edge of the wood so you don’t have to hold it with your hands. I usually hold the paper by itself, but you just have to be aware of the blade and where your fingers are. Although this method is more forgiving than stone, a consistent angle will yield the best results.