Most people use a circular saw blade to cut wood, but it is also possible to find one for use on metals and plastics. When sharpening it, make sure you fasten it on the machine or it will recoil and snap loose. You also need protective gear because the chippings from the friction might get into your eyes. Do not allow children or even adults to hover around the area while you are sharpening a circular saw blade. Most importantly, do not use your thumb to check its sharpness.