NPT Size	Tap Drill Size (in.)	(Decimal) (in.)
1/16 - 27	"C"	(0.242)
1/8 - 27	"Q"	(0.332)
1/4 - 18	7/16	(0.438)
3/8 - 18	9/16	(0.562)
1/2 - 14	45/64	(0.703)
3/4 - 14	29/32	(0.906)
1.0 - 11•1/2	1•9/64	(1.141)
1•1/4 - 11•1/2	1•31/64	(1.484)
1•1/2 - 11•1/2	1•23/32	(1.719)
2.0 - 11•1/2	2•3/16	(2.188)
2•1/2 - 8	2•39/64	(2.609)
3.0 - 8	3•15/64	(3.234)