Precision Self-Centering Drill BitPrecision Self-Centering Drill Bits are essential for pilot holes in hinges, handles, drawer slides and other parts, the cone that surrounds the drill ensures centering of the pilot hole with respect to when countersinking the mounting hole drill a pilot hole Sharp135 degree oblique edge of the bit head, make the hinge drill faster drilled in the position of the hinge holes.the guide surrounding the forest is pushed by a spring to keep it in contact with the milling of the part to be repaired. Wood chips are automatically discharged Sawdust is automatically discharged from both sides of the holes, without a drill blocked, you don't need to remove the wood chips, effectively increasing your work Easy to use and install Different hardness wood, need different centering drill, just remove the screw and replace er the drill. Professional tutorials on how to use vedio will be provided.