Hanson 1903ZR Tap 1/4"-18Npt Taper, for Tap Die Extraction Each taper tap is used to cut internal threads in pipes This taper tap is ideal for pipe fittings Taps are tapered at a rate of 3/4 inches per foot Nominal size of the tap is that of the pipe fitting being tapped 1/4" size with 18 NPT (National Pipe Taper)