NPT - American tapered pipe
1/4-18 NPT pipe thread: 18 TPI, major Ø 13.72 mm.
Profile
| Designation | 1/4-18 NPT |
|---|---|
| Major (outside) diameter | 13.72 mm · 0.5402" |
| Pitch | 1.411 mm · 18 TPI |
| Pitch diameter | 12.803 mm · 0.5041" |
| Minor diameter (external) | 11.989 mm · 0.472" |
| Minor diameter (internal) | 12.192 mm · 0.48" |
| Recommended tap drill | 11.11 mm |
Pipe threads are made up to a seal against the mating flanks, not tightened to a bolt preload, so no proof load or tightening-torque figure applies.
The bolt schedule collects the fasteners for one job onto a single sheet - tap drill, wrench size, grade and tightening torque on every line, taken straight from pages like this one. Free schedules hold 3 lines and are saved in this browser only.
1/4-18 NPT is a NPT pipe thread running at 18 threads per inch on a 13.72 mm major diameter. NPT is a 60° tapered thread that seals on the flanks; use a tapered reamer after drilling for a full-form thread.
All values are generated from the standard thread formulas (ISO 68-1 / ASME B1.1) and published standard tables - not hand-entered. See the full reference.
Drill 11.11 mm before tapping 1/4-18 NPT. NPT is a 60° tapered thread that seals on the flanks; use a tapered reamer after drilling for a full-form thread.
1/4-18 NPT is tapered. NPT is a 60° tapered thread that seals as the flanks wedge together, normally with thread sealant or PTFE tape.
1/4-18 NPT runs at 18 threads per inch, a pitch of 1.411 mm, on a major diameter of 13.72 mm.
No. Pipe threads are made up to a seal against the mating flanks, not tightened to a bolt preload, so no proof load or tightening-torque figure applies.
The pipe this thread runs on
NPS 1/4 pipe is 0.54 in across the outside whatever the schedule; at standard wall (std) the wall is 0.088 in and the bore 0.364 in.
Full dimensions for the standard wall · every schedule in the chart
Nearby sizes