Thread series · NPTF

NPTF Dryseal Pipe Thread Thread Chart — All Sizes, Dimensions & Tap Drills

Name: NPTF Dryseal Pipe Thread thread dimensions and tap drill sizes
Creator: ShopMath

https://shopmath.org/threads/nptf · data verified August 1, 2026

The NPTF Dryseal Pipe Thread series covers 10 standard sizes, from 1/16-27 NPTF to 2-11.5 NPTF, and 10 of them carry a tap drill recommendation. Dryseal taper pipe thread, ASME B1.20.3 — crest and root interfere to seal without tape.

Sizes: 10
Smallest: 1/16-27 NPTF
Largest: 2-11.5 NPTF
Standard: ASME B1.20.1, ASME B1.20.3; public-domain primary FED-STD-H28/7A (1984)

Every NPTF Thread Size — Dimensions and Tap Drills

10 sizes, ordered smallest to largest. Every row links to the full page for that thread, with class limits, clearance holes and tap drills across 50–85% engagement.

NPTF Dryseal Pipe Thread thread sizes — basic dimensions and tap drills
Property	Property	Major Ø		Pitch Ø		Minor Ø		Tap drill
Thread	TPI	in	mm	in	mm	in	mm	Drill	in	mm
1/16-27 NPTF	27	0.3125	7.938	0.2812	7.142	0.2516	6.391	E	0.2500	6.350
1/8-27 NPTF	27	0.4050	10.287	0.3736	9.489	0.3440	8.738	11/32	0.3438	8.731
1/4-18 NPTF	18	0.5400	13.716	0.4916	12.487	0.4472	11.359	7/16	0.4375	11.113
3/8-18 NPTF	18	0.6750	17.145	0.6270	15.926	0.5826	14.798	37/64	0.5781	14.684
1/2-14 NPTF	14	0.8400	21.336	0.7784	19.772	0.7213	18.321	23/32	0.7188	18.256
3/4-14 NPTF	14	1.0500	26.670	0.9889	25.117	0.9317	23.665	59/64	0.9219	23.416
1-11.5 NPTF	12	1.3150	33.401	1.2386	31.461	1.1691	29.695	1	1.0000	25.400
1 1/4-11.5 NPTF	12	1.6600	42.164	1.5834	40.218	1.5138	38.450	1	1.0000	25.400
1 1/2-11.5 NPTF	12	1.9000	48.260	1.8223	46.287	1.7528	44.521	1	1.0000	25.400
2-11.5 NPTF	12	2.3750	60.325	2.2963	58.325	2.2267	56.558	1	1.0000	25.400

Basic dimensions are the theoretical values before a tolerance class is applied. Tap drills are for cut taps at the default engagement; per-size pages carry 50–85%.

Sources and Method for the NPTF Thread Chart

NPTF thread dimensionscomputed+compiled

ASME B1.20.1 taper pipe thread formulas; E0 and L2 reproduced to 5 decimals in docs/research/data-sourcing.md §3.3. Public-domain primary: FED-STD-H28/7A (1984).; pipe OD / tpi / L1 / L4: ASME B1.20.1 pipe OD / tpi / L1 / L4 via Wikipedia National pipe thread (CC BY-SA 4.0); OD and tpi cross-checked against FreeCAD FeatureHole.cpp NPT block (LGPL-2.1+). NPTF shares the NPT taper geometry; dryseal crest/root truncation limits are NOT included (single-source only — see generator header).

Verified against Wikipedia National pipe thread standard-sizes table (CC BY-SA 4.0) — 98 checks passed to 1e-5 in

Part computed from the standard's formulas, part compiled from agreeing public sources.

Assumptions

Tap drill figures are for cut taps at the default thread engagement; each size page carries the full 50–85% range.
Dataset scope: L1 is tabulated, not derivable (data-sourcing.md §3.3). EXCLUDED: NPTF crest/root truncation limits (single-sourced), NPSM/NPSC/NPSF straight pipe threads, BSPT/BSPP.

Data last verified

August 1, 2026

How this data is built and checked →

How to Cite This NPTF Thread Chart

Citation

ShopMath. "NPTF Dryseal Pipe Thread Thread Chart — All Sizes, Dimensions & Tap Drills." ShopMath, verified August 1, 2026, https://shopmath.org/threads/nptf

BibTeX

@misc{shopmath-threads-nptf,
  title        = {NPTF Dryseal Pipe Thread Thread Chart — All Sizes, Dimensions & Tap Drills},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/threads/nptf}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/threads/nptf

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