Unified Thread Spec Table
This specification follows ANSI/ASME (American National Standards). Inch-based units apply; required for maintaining US/Canadian equipment and meeting North American market requirements.
Inch-based (UNC/UNF) screws following North American/British standards. Required for maintaining US-imported equipment.
Practical Notes
- Looks similar to metric but pitch differs — never mix. Forced assembly destroys threads.
- Unified fasteners are hard to source domestically. Stock spares in advance for imported equipment maintenance.
Selection Guide
For maintaining US/UK-origin equipment. UNC (coarse) and UNF (fine) threads are incompatible with metric — never mix. Availability may be limited domestically; prefer metric for new designs, reserve unified threads for imported equipment maintenance only.
ANSIUnified Thread
10 sizes| Nominal | d | P | Head Dia | Wrench | Other |
|---|---|---|---|---|---|
| 1/4"-20 UNC | - | 1.27 | - | - | - |
| 5/16"-18 UNC | - | 1.41 | - | - | - |
| 3/8"-16 UNC | - | 1.59 | - | - | - |
| 1/2"-13 UNC | - | 1.95 | - | - | - |
| 5/8"-11 UNC | - | 2.31 | - | - | - |
| 3/4"-10 UNC | - | 2.54 | - | - | - |
| 1"-8 UNC | - | 3.18 | - | - | - |
| 1/4"-28 UNF | - | 0.91 | - | - | - |
| 3/8"-24 UNF | - | 1.06 | - | - | - |
| 1/2"-20 UNF | - | 1.27 | - | - | - |
Key Features
- Inch-based UNC (coarse) / UNF (fine) thread system; US/UK standard compatible
- 60° thread angle; incompatible pitch/OD with metric threads—avoid mixing
- Range #0 (1.524 mm) to 2 in; SAE Grade 2/5/8 strength classification
Key Applications
US-origin machine maintenance, aircraft (AN/NAS), imported automotive parts, oil & gas equipment, defense
FAQ
Difference between UNC and UNF?
UNC (coarse) for general fastening; UNF (fine) for vibration-prone applications. Same concept as metric coarse/fine threads.