Milwaukee Thunderbolt black Oxide Jobber length drill bits are for immoderate durability and monthlong life. The Thunderbolt web a thicker core than a casebook drill bit, which provides final strength and protects against side-load breakage. A specially designed story flute form chips and debris fast-breaking to keep the bit unresponsive. A precision, 135 Split Point tip starts on contact to keep the bit from walking for fast-breaking straight holes. first-class for drilling on falciform surfaces, less effort to drill and is highly recommended for use with movable drills. The 3-Flat Secure-Grip shank wo n't in the drill chuck. Reduced shank for use in 3/8-Inch chucks.