1-1/2 NPT Tap Drill Size and Pipe Thread Bit
Use a 1-47/64 drill bit
1-1/2-11½ NPT · 1.7344 in / 44.05 mm · pipe taper
1-1/2 NPT (1-1/2-11½) is a large tapered pipe thread for main supply lines, pump inlets and large pneumatic fittings. The drill is 1-47/64 in, sized to the pipe taper at the gauge plane.
At a glance
| Tap drill | 1-47/64 |
|---|---|
| Inches | 1.7344 in |
| Millimetres | 44.05 mm |
| Threads per inch | 11½ |
| Thread form | NPT taper pipe (1:16 taper) |
Why this size
NPT is a taper pipe thread. The drill is sized to the pipe minor diameter at the gauge plane. Tap drill: 1-47/64 (1.7344 in / 44.05 mm).
Because NPT threads taper, the drill is not set by the percent-engagement rule used for machine screws. 1-47/64 in is the correct tap drill for 1-1/2 NPT — the same standard the 3/4 (59/64) and 1 in (1-5/32) sizes follow.
Related sizes
Nearby NPT sizes
Every common pipe taper size, smallest to largest: