1/8 NPT Thread Specs
Standard: ASME B1.20.1 (NPT)
Technical parameters and design data for the 1/8 NPT pipe thread.
Established under standard ASME B1.20.1, this thread uses a pitch of 0.03704 inches and has 27 threads per inch.
Often used in fluid, hydraulic, or pneumatic systems, NPT/BSP threads require suitable thread sealants to assure leak-tight performance.
Dimensional Specifications
Size Designation
1/8 NPT
Nominal Diameter
0.405 in(10.29 mm)
Major Diameter
0.4985 in(12.66 mm)
TPI (Threads per Inch)
27
Pitch
0.03704 in
Pitch Diameter
0.4744 in(12.05 mm)
Minor Diameter
0.4584 in(11.64 mm)
Tap Drill size
21/64 in
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Frequently Asked Questions
What is the tap drill size for 1/8 NPT pipe thread?
The recommended tap drill size for a 1/8 NPT pipe thread is 21/64 inches.
What is the major diameter of a 1/8 NPT pipe thread?
For a standard 1/8 NPT pipe thread, the major diameter at the pipe reference plane is 0.4985 inches (approx. 12.66 mm).