2-1/2 NPT Thread Specs
Standard: ASME B1.20.1 (NPT)
Technical parameters and design data for the 2-1/2 NPT pipe thread.
Established under standard ASME B1.20.1, this thread uses a pitch of 0.125 inches and has 8 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
2-1/2 NPT
Nominal Diameter
2.875 in(73.02 mm)
Major Diameter
3.2798 in(83.31 mm)
TPI (Threads per Inch)
8
Pitch
0.125 in
Pitch Diameter
3.1986 in(81.24 mm)
Minor Diameter
3.1445 in(79.87 mm)
Tap Drill size
2-5/8 in
Quick Unit Converter
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Frequently Asked Questions
What is the tap drill size for 2-1/2 NPT pipe thread?
The recommended tap drill size for a 2-1/2 NPT pipe thread is 2-5/8 inches.
What is the major diameter of a 2-1/2 NPT pipe thread?
For a standard 2-1/2 NPT pipe thread, the major diameter at the pipe reference plane is 3.2798 inches (approx. 83.31 mm).