TAP DRILL SIZE CHART FOR NPT THREADS
(National Pipe Threads)

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 - 111/2 19/64 (1.141)
11/4 - 111/2 131/64 (1.484)
11/2 - 111/2 123/32 (1.719)
2.0 - 111/2 23/16 (2.188)
21/2 - 8 239/64 (2.609)
3.0 - 8 315/64 (3.234)


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