Drill/Tap/Countersink, High Speed Steel, 5/16"-18, Bright (Uncoated) Finish

These combination tools drill a hole and create threads in the hole in one pass. They also create a countersink at the top of the hole that allows a screw to sit flush with the top of the hole and helps prevent the workpiece material from swelling when the screw is inserted in the hole and tightened down. These combination drills, taps, and countersinks are made from high-speed steel and provide good wear resistance in general purpose applications in a range of materials, including ferrous and nonferrous metals.