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Sizes · Pipe (NPT / BSPT / BSPP)

NPT — American tapered pipe

1-11.5 NPT

1-11.5 NPT pipe thread: 11.5 TPI, major Ø 33.4 mm.

Tap-drill calculatorIdentify a thread
Tap drill
29.36 mm
33.4 mm major Ø

Profile

Thread form & key diameters

Major Ø 33.4 mmP 2.209 mm60°Root Ø 30.69 mm · Pitch Ø 31.965 mm1-11.5 NPT11.5 TPI · 60° form

Dimensions

Designation1-11.5 NPT
Major (outside) diameter33.4 mm · 1.315"
Pitch2.209 mm · 11.5 TPI
Pitch diameter31.965 mm · 1.2585"
Minor diameter (external)30.69 mm · 1.2083"
Minor diameter (internal)31.009 mm · 1.2208"
Recommended tap drill29.36 mm

What tap drill do I need for 1-11.5 NPT?

1-11.5 NPT is a NPT pipe thread running at 11.5 threads per inch on a 33.4 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.

Nearby sizes

More npt — american tapered pipe threads

3/4-14 NPTTap 23.42 mmØ 26.67 mm · pitch 1.814 mm1-1/4-11.5 NPTTap 38.1 mmØ 42.16 mm · pitch 2.209 mm1/2-14 NPTTap 17.86 mmØ 21.34 mm · pitch 1.814 mm1-1/2-11.5 NPTTap 44.05 mmØ 48.26 mm · pitch 2.209 mm3/8-18 NPTTap 14.68 mmØ 17.15 mm · pitch 1.411 mm1/4-18 NPTTap 11.11 mmØ 13.72 mm · pitch 1.411 mm1/8-27 NPTTap 8.74 mmØ 10.29 mm · pitch 0.941 mm1/16-27 NPTTap 6.35 mmØ 7.94 mm · pitch 0.941 mm