Star-M 601 range of Drill Bits are precision milled and cuts cleaner than any drill bit you'll ever encounter. This is achieved by having the pin perfectly in the center of the drill, which will always create a centred hole. These super clean cut drill bits are extremely efficient in both cross cut as well as with the grain. Designed specifically for soft materials like wood, hard wood, rubber, acrylic board and PVC that can otherwise be problematic to drill, the knife-like flutes of the Star-M bits deliver precise cuts in even more fibrous materials, such as bamboo. Hooked spurs clear any remaining waste from the perimeter of the cut, these are followed by semi-circular wings that incise a little deeper to part the waste from the surrounding material. A curved cutting edge then planes the waste out and sends it up the flutes. For plastics use a low speed setting, for fibrous materials use your highest speed setting, and in both cases introduce the bit to the material gradually. Specifications: Diameter Range: 3mm - 22mm Overall length: 80mm - 125mm Spiral length; 40mm-75mm Shank shape: Hex Average weight: 20g