IRWIN 1869393 WeldTec Self-Feed Wood Drilling Bit, 3 5/8-Inch Innovative welded cutting edge for extreme life in tough materials, including nail-embedded wood Replaceable screw-point tip is larger and more durable and pulls bit fast for clean, true holes versus previous IRWIN self-feed bits 7/16" hex quick-change shank reduces slipping in standard chucks and is compatible with all 7/16" impact drills