Pre Tap Drill Size

Pipe Tap NPT & NPTF

Tap
Drill Size
Decimal Equivalent
2 - 11-1/2
2in 3/16
2.1875
1-1/2 - 11-1/2
1in 23/32
1.7187
1-1/4 - 11-1/2
1in 31/64
1.4843
1 - 11-1/2
1in 9/64
1.1406
3/4 - 14
29/32
0.9062
1/2 - 14
45/64
0.7031
3/8 - 18
9/16
0.5625
1/4 - 18
7/16
0.4375
1/8 - 27
Q
.332
1/16 - 27
C
.242