What is the tap drill size for 3/4-14 NPT?

The tap drill for 3/4-14 NPT is 59/64 — 0.9219 in (23.416 mm). Taper pipe threads are tapped with a taper tap and sealed with compound or tape.

What is the pitch diameter of 3/4-14 NPT?

The basic pitch diameter of 3/4-14 NPT is 0.9889 in (25.117 mm).

What is the minor diameter of 3/4-14 NPT?

The basic minor diameter of 3/4-14 NPT is 0.9317 in (23.665 mm). That is the theoretical root of the internal thread, not the drilled hole size — see the tap drill table for the hole to drill.

What is the thread pitch of 3/4-14 NPT?

3/4-14 NPT has 14 threads per inch, a pitch of 0.0714 in (1.814 mm).

What is the hand-tight engagement length (L₁) of 3/4-14 NPT?

The hand-tight engagement length L₁ for 3/4-14 NPT is 0.3390 in (8.611 mm), on a pipe outside diameter of 1.0500 in (26.670 mm).

NPT Taper Pipe Thread · 3/4-14 NPT

3/4-14 NPT Thread — Dimensions, Tap Drill & Clearance

https://shopmath.org/threads/npt/3-4 · data verified August 1, 2026

The tap drill for 3/4-14 NPT taper pipe thread is 59/64 — 0.9219 in (23.416 mm). Basic pitch diameter is 0.9889 in (25.117 mm) and basic minor diameter is 0.9317 in (23.665 mm).

Series: NPT Taper Pipe Thread
Designation: 3/4-14 NPT
TPI: 14
Standard: ASME B1.20.1, ASME B1.20.3; public-domain primary FED-STD-H28/7A

Tap drill · taper pipe tap

59/64

Drill Ø: 0.9219in
Drill Ø: 23.416mm

NPT and NPTF holes are drilled straight and cut with a taper tap. The standard assumes a sealing compound or tape on the joint.

Basic Thread Dimensions for 3/4-14 NPT

Basic thread dimensions — 3/4-14 NPT
Property	Inch	Millimetre
Basic major diameter	1.0500	26.670
Threads per inch	14	—
Pitch	0.0714	1.814
Basic pitch diameter	0.9889	25.117
Basic minor diameter	0.9317	23.665
Sharp V thread height (H)	0.0619	1.571

Threads per inch has no millimetre counterpart — metric threads are specified by pitch instead. Basic dimensions are the theoretical values before any tolerance class is applied.

Taper Pipe Thread Geometry for 3/4-14 NPT

3/4-14 NPT is a taper thread: the diameter changes along the thread, so every diameter below is stated at a named plane. The taper is 0.7500 in per foot on diameter.

Taper pipe thread geometry — 3/4-14 NPT
Property	Inch	Millimetre
Pipe outside diameter	1.0500	26.670
Taper on diameter, per foot	0.7500	19.050
Pitch Ø at end of pipe (E₀)	0.9677	24.579
Pitch Ø at hand-tight plane (E₁)	0.9889	25.117
Pitch Ø at effective plane (E₂)	1.0018	25.445
Hand-tight engagement (L₁)	0.3390	8.611
Effective thread length (L₂)	0.5457	13.861
Overall external thread length (L₄)	0.7935	20.155
Thread height (h)	0.0571	1.451
Sharp V height (H)	0.0619	1.571
Minor Ø at hand-tight plane	0.9317	23.665

ASME B1.20.1 publishes these dimensions in inches only; the millimetre column is an exact conversion (1 in = 25.4 mm by definition). L₁ is the hand-tight engagement length and is tabulated in the standard, not derived.

Other Thread Pitches in the Same Size as 3/4-14 NPT

A 3/4 fastener is not always 3/4-14 NPT. These are the other standard pitches cut on the same nominal size.

Other standard pitches at nominal size 3/4
Thread	Series	Pitch	Tap drill
3/4-14 NPTF	NPTF Dryseal Pipe Thread	14 TPI	59/64

Sources and Method for 3/4-14 NPT

Basic dimensions · Taper pipe geometrycomputed+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+)

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

NPT threads are not a seal on their own — the standard assumes a sealing compound or tape on the joint.
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 3/4-14 NPT Reference

Citation

ShopMath. "3/4-14 NPT Thread — Dimensions, Tap Drill & Clearance." ShopMath, verified August 1, 2026, https://shopmath.org/threads/npt/3-4

BibTeX

@misc{shopmath-threads-npt-3-4,
  title        = {3/4-14 NPT Thread — Dimensions, Tap Drill & Clearance},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/threads/npt/3-4}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/threads/npt/3-4

Common Questions About 3/4-14 NPT

What is the tap drill size for 3/4-14 NPT?: The tap drill for 3/4-14 NPT is 59/64 — 0.9219 in (23.416 mm). Taper pipe threads are tapped with a taper tap and sealed with compound or tape.
What is the pitch diameter of 3/4-14 NPT?: The basic pitch diameter of 3/4-14 NPT is 0.9889 in (25.117 mm).
What is the minor diameter of 3/4-14 NPT?: The basic minor diameter of 3/4-14 NPT is 0.9317 in (23.665 mm). That is the theoretical root of the internal thread, not the drilled hole size — see the tap drill table for the hole to drill.
What is the thread pitch of 3/4-14 NPT?: 3/4-14 NPT has 14 threads per inch, a pitch of 0.0714 in (1.814 mm).
What is the hand-tight engagement length (L₁) of 3/4-14 NPT?: The hand-tight engagement length L₁ for 3/4-14 NPT is 0.3390 in (8.611 mm), on a pipe outside diameter of 1.0500 in (26.670 mm).

All NPT Taper Pipe Thread sizes · Every thread series