Thread series · UNF

Unified Fine (UNF) Thread Chart — All Sizes, Dimensions & Tap Drills

Name: Unified Fine (UNF) thread dimensions and tap drill sizes
Creator: ShopMath

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

The Unified Fine (UNF) series covers 24 standard sizes, from #0-80 UNF to 1 1/2"-12 UNF, and 24 of them carry a tap drill recommendation. The Unified fine inch thread series — more threads per inch, better hold in thin material.

Sizes: 24
Smallest: #0-80 UNF
Largest: 1 1/2"-12 UNF
Standard: ASME B1.1 (reference values based on the ASME B1.1 system; not a compliance claim)

Every UNF Thread Size — Dimensions and Tap Drills

24 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.

Unified Fine (UNF) 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
#0-80 UNF	80	0.0600	1.524	0.0519	1.318	0.0465	1.181	3/64	0.0469	1.191
#1-72 UNF	72	0.0730	1.854	0.0640	1.626	0.0580	1.473	#53	0.0595	1.511
#2-64 UNF	64	0.0860	2.184	0.0759	1.928	0.0691	1.755	#50	0.0700	1.778
#3-56 UNF	56	0.0990	2.515	0.0874	2.220	0.0797	2.024	#45	0.0820	2.083
#4-48 UNF	48	0.1120	2.845	0.0985	2.502	0.0894	2.271	#42	0.0935	2.375
#5-44 UNF	44	0.1250	3.175	0.1102	2.799	0.1004	2.550	#37	0.1040	2.642
#6-40 UNF	40	0.1380	3.505	0.1218	3.094	0.1109	2.817	#33	0.1130	2.870
#8-36 UNF	36	0.1640	4.166	0.1460	3.708	0.1339	3.401	#29	0.1360	3.454
#10-32 UNF	32	0.1900	4.826	0.1697	4.310	0.1562	3.967	#21	0.1590	4.039
#12-28 UNF	28	0.2160	5.486	0.1928	4.897	0.1773	4.503	#14	0.1820	4.623
1/4"-28 UNF	28	0.2500	6.350	0.2268	5.761	0.2113	5.367	#3	0.2130	5.410
5/16"-24 UNF	24	0.3125	7.938	0.2854	7.249	0.2674	6.792	I	0.2720	6.909
3/8"-24 UNF	24	0.3750	9.525	0.3479	8.837	0.3299	8.380	Q	0.3320	8.433
7/16"-20 UNF	20	0.4375	11.113	0.4050	10.287	0.3834	9.738	25/64	0.3906	9.922
1/2"-20 UNF	20	0.5000	12.700	0.4675	11.874	0.4459	11.326	29/64	0.4531	11.509
9/16"-18 UNF	18	0.5625	14.287	0.5264	13.371	0.5024	12.761	33/64	0.5156	13.097
5/8"-18 UNF	18	0.6250	15.875	0.5889	14.958	0.5649	14.348	37/64	0.5781	14.684
3/4"-16 UNF	16	0.7500	19.050	0.7094	18.019	0.6823	17.330	11/16	0.6875	17.462
7/8"-14 UNF	14	0.8750	22.225	0.8286	21.046	0.7977	20.262	13/16	0.8125	20.637
1"-12 UNF	12	1.0000	25.400	0.9459	24.026	0.9098	23.109	59/64	0.9219	23.416
1 1/8"-12 UNF	12	1.1250	28.575	1.0709	27.201	1.0348	26.284	1	1.0000	25.400
1 1/4"-12 UNF	12	1.2500	31.750	1.1959	30.376	1.1598	29.459	1	1.0000	25.400
1 3/8"-12 UNF	12	1.3750	34.925	1.3209	33.551	1.2848	32.634	1	1.0000	25.400
1 1/2"-12 UNF	12	1.5000	38.100	1.4459	36.726	1.4098	35.809	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 UNF Thread Chart

UNF thread dimensionscomputed

NBS Handbook H28 (1969) Part I §§6-7 (public domain, 17 U.S.C. 105); normative modern reference ASME B1.1; series membership: Series membership: threadlib UIS_thread.csv (BSD-3-Clause); cross-checked against NBS H28 (1969) Part I Table 2.21; clearance holes: ISO 273 (metric) and ASME B18.2.8 (inch) via FreeCAD FeatureHole.cpp (LGPL-2.1+), cross-checked against bd_warehouse clearance_hole_sizes.csv (Apache-2.0)

Verified against NBS H28 (1969) Part I, Table 2.21 (public domain); cross-checked against FreeCAD CAM thread tables (LGPL-2.1+) — 1064 checks passed at 0.0001 in

Computed from the standard's formulas, then checked against published tables.

Assumptions

Tap drill figures are for cut taps at the default thread engagement; each size page carries the full 50–85% range.
Dataset scope: Le = 1D for UNC/UNF, 9P for UNEF — determined empirically against H28 Table 2.21, resolving data-sourcing.md open item 5. EXCLUDED: form (roll) tap drills, class 1A/1B limits, class 1AR allowances, constant-pitch UN series.

Data last verified

August 1, 2026

How this data is built and checked →

How to Cite This UNF Thread Chart

Citation

ShopMath. "Unified Fine (UNF) Thread Chart — All Sizes, Dimensions & Tap Drills." ShopMath, verified August 1, 2026, https://shopmath.org/threads/unf

BibTeX

@misc{shopmath-threads-unf,
  title        = {Unified Fine (UNF) Thread Chart — All Sizes, Dimensions & Tap Drills},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/threads/unf}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/threads/unf

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