Union Butterfield TN1541 High-Speed Steel Pipe Tap, NPT, Medium Hook, TiN Coated, Round Shank With Square End, 1/4"-18 Thread Size Pipe tap cuts threads in pipes and pipe fittings NPT (National Pipe Taper) thread for compatibility with a range of threads Titanium nitride (TiN) coating combines hardness with low friction for extended tool life and faster cutting Straight flutes to cut threads in through holes and blind holes Medium hook for general-purpose pipe tapping