TAP NATIONAL PIPE THREAD 3/4-14 NPT - NATIONAL PIPE THREAD TAPS. PRECISION CUT THREADS ACCURATELY FORMED FOR CONSISTENT EXACT THREADING. HEAT TREATED AND TEMPERED FOR FILE HARD THREADS AND LONGER USEFUL LIFE. DESIGNED FOR HAND CUTTING APPLICATIONS. NATIONAL PIPE THREAD TAP SIZES FOR INTERNAL THREADING ON ALL TYPES OF PIPES.