Union Butterfield 1994(UNF) High-Speed Steel Combination Drill and Tap, Uncoated (Bright) Finish, Round Shank With Square End, 1/2"-20 Thread Size Combination drill and tap creates holes and cuts threads in one operation for efficient tooling Spiral flute tap design pulls chips back from the tip of the tool and out of the hole to prevent clogging Designed for creating and threading through holes Available in UNC (Unified Coarse) or UNF (Unified Fine) right-hand thread options for different applications Round shank with square end helps to minimize rotation in the tool holder