Thread Quick Reference
Metric threads use M (e.g. M8×1.25 — 8 = diameter, 1.25 = pitch). Fine threads give slightly higher strength and finer adjustment. Imperial threads use UNC (coarse) and UNF (fine).
| Metric size | Coarse pitch (mm) | Fine pitch (mm) |
|---|---|---|
| M1.4 – M3 | 0.30 – 0.50 | 0.20 – 0.35 |
| M4 – M6 | 0.70 – 1.00 | 0.50 – 0.75 |
| M8 – M12 | 1.25 – 1.75 | 1.00 – 1.50 |
| M14 – M24 | 2.00 – 3.00 | 1.50 – 2.00 |
| M27 – M36 | 3.00 – 4.00 | 1.50 – 3.00 |
| M42 – M48 | 4.50 – 5.00 | 2.00 – 3.00 |
Common Fine Threads
- M8×1.0, M10×1.25 / 1.0, M12×1.5 / 1.25, M16×1.5, M20×1.5
- Fine threads suit adjustment, locking and thin-wall applications.
Imperial UNC / UNF
- UNC coarse: #4-40, #6-32, #8-32, #10-24, 1/4-20, 3/8-16, 1/2-13, 5/8-11, 3/4-10
- UNF fine: #4-48, #6-40, #8-36, #10-32, 1/4-28, 3/8-24, 1/2-20, 5/8-18, 3/4-16
Thread Tolerance
- External thread: commonly 6g (mates with 6H internal); custom 4h / 6e available.
- Internal thread: commonly 6H for nuts and tapped holes.
- Inspection: GO / NO-GO gauges verify fit.
Unsure of thread size? Compare with a thread gauge or send a photo — we confirm.