---
type: "thread-series"
series: "unf"
name: "Unified Fine (UNF)"
system: "unified"
size_count: 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)"
verified: "August 1, 2026"
url: https://shopmath.org/threads/unf
---

# Unified Fine (UNF) Thread Chart — All 24 Sizes, Dimensions & Tap Drills

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

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.

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

- **Source**: 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)
- **Method**: computed
- **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

### 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

## Related pages

- Every thread series: [Screw thread reference](https://shopmath.org/threads.md)
- Cross-series chart: [Tap drill chart](https://shopmath.org/charts/tap-drill.md)
- Drill index: [Drill size chart](https://shopmath.org/charts/drill-sizes.md)

---

*Source: [ShopMath](https://shopmath.org/threads/unf) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*