5625-12, Limit H3, Number of Flutes 4 Hand taps are popular for use in general machine tapping or CNC tapping. They are also appropriate for tapping the vast majority of materials in through or blind holed conditions.
. 3/8"-18 NPT HSS 4 Flute Pipe Tap NPT threads require the use of a "sealer" like teflon tape or pipe compound. The nominal size of a Pipe Tap is that of the pipe fitting to be tapped, not the actual size of the tap.