The hardest and most wear-resistant bits, these deliver coolant to reduce heat and evacuate chips. They are designed for CNC machines that supply coolant through the spindle rather than an external source, such as a hose and nozzle. Coolant flows directly from holes in the bit's tip onto the drilling surface. This speeds up cuts and leads to excellent performance in deep holes and tough materials such as stainless steel and titanium.

The flutes spiral in the opposite direction of other bits and stay sharp longer than high-speed steel. They’re primarily used to remove stripped screws. Choose a bit that’s slightly smaller than the diameter of the screw’s head. Set your power tool to rotate in reverse. Slowly drill in the center of the screw head, maintaining constant pressure. As the bit penetrates, it will catch onto the screw and reverse it out of the hole. If the screw is badly stripped, you might need to punch a starter hole. Also known as reverse-flute bits.