Pipe Taper Tap, 0.25-In. x 18
1/4" xÊ18 NPT, Carbon Steel, National Pipe Taper Tap, Ideal For Pipe Fittings, Cuts Internal Threads In Piped, Norml Size Of The Tap Is That Of The Pipe Being Fitted, Tapered At A Rate Of 3/4" Per Foot, Use 7/16" Drill Bit.