#0-80 UNF Thread Dimensions and Tap Drill
#0-80 UNF is the Unified fine thread for the number 0 size (major diameter 0.060 in, 1.52 mm): 80 threads per inch, a pitch of 0.01250 in (0.318 mm), on a 60° profile. ASME B1.1 lists it in the UNF series.
- Tap drill3/64"81% thread, 1.19 mm
- Pitch80 TPI0.318 mm
- Major diameter0.0600 in1.524 mm
- Pitch diameter0.0519 in1.318 mm
- Minor diameter (nut)0.0465 in1.180 mm
- Tensile stress area0.00180 in²1.16 mm²
- Clearance hole#48normal fit, ASME B18.2.8
Thread profile
#0-80 UNF basic dimensions
| Dimension | in | mm |
|---|---|---|
| Major diameter d = D | 0.0600 | 1.524 |
| Pitch P | 0.01250 | 0.318 |
| Pitch diameter d2 = D2 | 0.0519 | 1.318 |
| Minor diameter, internal thread D1 | 0.0465 | 1.180 |
| Minor diameter, external UNR thread d3 | 0.0451 | 1.146 |
| Height of fundamental triangle H | 0.0108 | 0.275 |
| Thread height, internal (5H/8) | 0.0068 | 0.172 |
| Thread height, external (11H/16) | 0.0074 | 0.189 |
| Crest flat of external thread (P/8) | 0.0016 | 0.040 |
| Crest flat of internal thread (P/4) | 0.0031 | 0.079 |
| Property | Value |
|---|---|
| Threads per inch | 80 |
| Flank angle | 60° (30° each side) |
| Lead angle at the pitch diameter | 4.39° |
| Tensile stress area As | 0.00180 in² (1.16 mm²) |
Basic (nominal) sizes per ASME B1.1, before tolerances. A UN external thread with a flat root has the same basic minor diameter as the nut (D1); d3 applies to the rounded UNR root.
#0-80 UNF limits of size (class 2A bolt, 2B nut)
Classes 2A and 2B are the general-purpose fits for commercial bolts, screws and nuts. The 2A external thread has an allowance of 0.0005 in, so its maximum size is that much below basic; the 2B nut starts at the basic size.
| External thread 2A | Max (in) | Min (in) | Tolerance (in) |
|---|---|---|---|
| Major diameter | 0.0595 | 0.0563 | 0.0032 |
| Pitch diameter | 0.0514 | 0.0496 | 0.0018 |
| Internal thread 2B | Max (in) | Min (in) | Tolerance (in) |
|---|---|---|---|
| Minor diameter | 0.0514 | 0.0465 | 0.0049 |
| Pitch diameter | 0.0542 | 0.0519 | 0.0023 |
Limits of size from ASME B1.1 Table 2.
#0-80 UNF tap drill size
Tap drill for #0-80 UNF: 3/64" (0.0469 in, 1.19 mm)
This leaves about 81% thread in the tapped hole.
3/64" is the drill listed for #0-80 UNF in standard tap drill charts. It is 0.0131 in under the 0.0600 in major diameter.
The 2B minor diameter of the finished nut thread must lie between 0.046 and 0.051 in. The recommended drill falls inside that band.
Other drills that work for #0-80 UNF
A larger drill cuts less thread and taps more easily; a smaller one gives a fuller thread but loads the tap harder.
| Drill | mm | in | % thread | Within 2B limits | Thread engagement |
|---|---|---|---|---|---|
| #56 | 1.18 | 0.0465 | 83% | yes | |
| 3/64"recommended | 1.19 | 0.0469 | 81% | yes | |
| 1.2 mm | 1.20 | 0.0472 | 79% | yes |
% thread = (major diameter − drill diameter) ÷ (1.299 × pitch). See the tap drill chart for how to choose a percentage.
Clearance hole for #0
The clearance hole depends only on the 0.0600 in diameter, not on the thread series. The normal fit, a #48 drill, is the usual choice for general assembly.
| Fit | Drill | Hole Ø (in) | Hole Ø (mm) | Clearance on Ø (in) |
|---|---|---|---|---|
| Close | #51 | 0.0670 | 1.70 | 0.0070 |
| Normal | #48 | 0.0760 | 1.93 | 0.0160 |
| Loose | 3/32 in | 0.0938 | 2.38 | 0.0338 |
Nominal drill sizes from ASME B18.2.8.
#0-80 UNF strength
SAE J429 starts at 1/4 in, so the SAE grades give no proof load for #0-80 UNF. For an estimate, multiply the tensile stress area of 0.00180 in² by the strength of the material: for example, 60,000 psi gives 108 lbf.
Closest metric thread
No metric thread is interchangeable with #0-80 UNF. The nearest is M1.6×0.35, which is 0.08 mm larger in diameter with a pitch of 0.350 mm against 0.318 mm. A nut may start on the wrong thread and then bind or strip, so identify by both diameter and pitch.
| Thread | Major Ø (mm) | Pitch (mm) | TPI | Ø difference (mm) |
|---|---|---|---|---|
| #0-80 UNF (this thread) | 1.524 | 0.318 | 80.00 | — |
| M1.6×0.35 | 1.600 | 0.350 | 72.57 | +0.076 |
How the #0-80 UNF dimensions are calculated
Every basic dimension follows from the major diameter and the pitch:
- P = 0.01250 in = 1 ÷ 80 threads per inch
- H = 0.866025 × P = 0.0108 in
- d2 = d − 0.649519 × P = 0.0600 − 0.0081 = 0.0519 in
- D1 = d − 1.082532 × P = 0.0600 − 0.0135 = 0.0465 in
- d3 = d − 1.190785 × P = 0.0600 − 0.0149 = 0.0451 in (external root, 11H/16 deep)
- As = 0.7854 × (d − 0.9743 × P)² = 0.7854 × 0.0478² = 0.00180 in²
- Lead angle = arctan(P ÷ (π × d2)) = 4.39°
Related sizes and tools
Sources: ASME B1.1 (profile, series, limits of size and stress area), ASME B18.2.8 (clearance holes), SAE J429 (mechanical properties) and the tap drill tables of Machinery’s Handbook. How this site checks its data. Last reviewed 29 September 2026.