Tap Drill Size  21/64

High Speed Steel Straight Thread Pipe Taps (NPS) are

designed for tapping holes or couplings for low pressure

work that will adjust at assembly to the taper of external

threads. A sealant must be used to secure a pressure tight

joint. They may be used to produce NPSC and NPSM

threads. (NPSF) Straight Thread Pipe Dryseal Taps do not

require a sealant. Dryseal is attained by metal to metal

contact. They are primarily used to tap holes that connect oil

and fuel lines.