M20 vs 3/4-10 UNC Screw Size Chart
Overview
Reference specifications for M20 metric and 3/4-10 UNC imperial fasteners. These large fasteners are commonly found in heavy machinery and structural assemblies.
Comparison Table
| Standard | Size | Diameter (mm) | Pitch / TPI | Tap Drill |
|---|---|---|---|---|
| Metric | M20 | 20.00 mm | 2.50 mm | 17.5 mm |
| Imperial | 3/4”-10 UNC | 19.05 mm | 10 TPI | 16.5 mm (21/32”) |
FAQ
Are M20 and 3/4 bolts the same?
No. An M20 bolt (20.00 mm) is nearly 1mm larger in diameter than a 3/4” bolt (19.05 mm). They are not interchangeable, and using the wrong nut will lead to immediate thread failure.
Source Standard
ISO 261 / ASME B1.1