Union Butterfield 1543(NPTF) High-Speed Steel Pipe Tap, Uncoated (Bright) Finish, Round Shank With Square End, 1/2"-14 Thread Size Pipe tap cuts threads in pipes and pipe fittings NPTF (National Pipe Taper Fuel) threads for leak-free seals without the use of sealants Straight flutes to cut threads in through holes and blind holes Medium hook for general-purpose pipe tapping Round shank with square end helps to minimize rotation in the tool holder