Combined Drill and Countersinks, also known as Center Drills, are generally used on a lathe for creating a countersunk locating hole for live, dead, and driven centers. That isn’t to say their usefulness stops there. With their unique combined geometry, these cutting tools can also be used to start and countersink a hole for a later drilling operation all without changing tools between spot drills and countersinks effectively eliminating at least one tool swap.
