Milwaukee Thunderbolt Black Oxide jobber length drill bits are designed for extreme durability and long life. The Thunderbolt web features a thicker core than a standard drill bit to provide ultimate strength and protect against side load breakage. A specially designed parabolic flute form clears chips fast, while the 3-Flat Secure-Grip shank holds the bit firmly in the drill chuck. The 135 degree split point tip delivers a precision start and prevents walking for fast, accurate holes. Effective for drilling on curved surfaces, Milwaukee Thunderbolt Black Oxide bits require less effort to drill through metal, wood and PVC and are highly recommended for use with portable drills. Extreme durability: Thicker web provides greater strength and longer life.135 degree split point tip starts on contact to prevent walking.The parabolic flute clears chips fast.Black oxide coating provides lubricity and resists corrosion of the bit.Reduced shank diameter for use in 3/8 in. chucks.Corrosion resistant - Black oxide coating helps resist corrosion of the bitVersatile reduced shank diameter for use in 3/8 in. chucks3-Flat Secure-Grip shank holds the bit firmly in the drill chuck for reduced slipping15/32 in. diameter