Screw Machine Drill Bit, Drill Bit Size 1/2 in, Drill Bit Point Angle 135 Degrees , Split Point, High Speed Steel, Black Oxide, Cutting Direction Right Hand, Decimal Equivalent 0.5000 These drill bits have a black-oxide finish that retains lubricants to improve the bits' wear resistance and chip flow. Black-oxide bits should only be used for drilling ferrous metals. Spiral-flute drill bits evacuate chips as the bits drill into a workpiece.High-speed steel screw-machine length drill bits provide more flexibility and absorb more shock and vibration than cobalt, powdered-metal, and carbide screw-machine length drill bits, making them suitable for use in manual drilling machines and handheld power tools. They may leave a rough finish on the hole. Screw-machine length drill bits are shorter tha.