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Sizes · Pipe (NPT / BSPT / BSPP)

NPT — American tapered pipe

1-1/4-11.5 NPT

1-1/4-11.5 NPT pipe thread: 11.5 TPI, major Ø 42.16 mm.

Tap-drill calculatorIdentify a thread
Tap drill
38.1 mm
42.16 mm major Ø

Profile

Thread form & key diameters

Major Ø 42.16 mmP 2.209 mm60°Root Ø 39.45 mm · Pitch Ø 40.725 mm1-1/4-11.5 NPT11.5 TPI · 60° form

Dimensions

Designation1-1/4-11.5 NPT
Major (outside) diameter42.16 mm · 1.6598"
Pitch2.209 mm · 11.5 TPI
Pitch diameter40.725 mm · 1.6034"
Minor diameter (external)39.45 mm · 1.5532"
Minor diameter (internal)39.769 mm · 1.5657"
Recommended tap drill38.1 mm

What tap drill do I need for 1-1/4-11.5 NPT?

1-1/4-11.5 NPT is a NPT pipe thread running at 11.5 threads per inch on a 42.16 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

1-1/2-11.5 NPTTap 44.05 mmØ 48.26 mm · pitch 2.209 mm1-11.5 NPTTap 29.36 mmØ 33.4 mm · pitch 2.209 mm3/4-14 NPTTap 23.42 mmØ 26.67 mm · pitch 1.814 mm2-11.5 NPTTap 56.36 mmØ 60.33 mm · pitch 2.209 mm1/2-14 NPTTap 17.86 mmØ 21.34 mm · pitch 1.814 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 mm2-1/2-8 NPTTap 67.06 mmØ 73.03 mm · pitch 3.175 mm