PIPE TAP DRILL SIZES
TAP SIZE	NPT TAP DRILL		NPS TAP DRILL
TPI = THREADS PER INCH	INCH	M/M	INCH	M/M
1/16 - 27 TPI	D	6.25	1/4	6.35
1/8 - 27 TPI	Q	8.45	11/32	8.75
1/4 - 18 TPI	7/16	11.00	7/16	11.50
3/8 - 18 TPI	9/16	14.50	37/64	15.00
1/2 - 14 TPI	45/64	18.00	23/32	18.50
3/4 - 14 TPI	29/32	23.00	59/64	23.50
1 - 11-1/2 TPI	1-9/64	29.00	1-5/32	29.50
1-1/4 - 11-1/2 TPI	1-31/64	38.00	1-1/2	38.85
1-1/2 - 11-1/2 TPI	1-47/64	44.00	1/3/4	44.50
2 - 11-1/2 TPI	2-13/64	56.00	2-7/32	57.00
2-1/2 - 8 TPI	2-5/8	66.68	2-21/32	67.47