HSS drill bits, or high-speed steel drill bits, are used for drilling operations on a variety of metals, plastics and wood. The hardness of an HSS drill bit allows for drilling at high speeds, yields better results and avoids overheating of both the bit and the material being drilled.
HSS drill bits are available in several varieties: molybdenum, tungsten, titanium coated or cobalt. Each has advantages and disadvantages, explains HowStuffWorks. Molybdenum bits, often in combination with tungsten, are good, heavy-duty bits. Titanium-coated bits are corrosion-resistant, but cannot be sharpened without loss of the coating. Cobalt bits perform better at high temperatures and can be sharpened, but are more expensive and also more brittle than the other two types.