M20×2.5 Thread Specifications
Complete dimensions for M20×2.5 coarse pitch thread per ISO 724. Pitch: 2.5mm (10.2 TPI equivalent).
Thread Dimensions
| Designation | M20×2.5 |
| Thread Series | ISO Metric Coarse |
| Pitch | 2.5 mm (10.2 TPI) |
| Major Diameter (d) | 20 mm (0.7874") |
| Pitch Diameter (d₂) | 18.3762 mm (0.7235") |
| Minor Diameter — External (d₁) | 16.9327 mm (0.6666") |
| Minor Diameter — Internal (D₁) | 17.2937 mm (0.6809") |
| Thread Depth | 1.3532 mm |
| Tensile Stress Area | 239.82 mm² |
| Fundamental Triangle Height (H) | 2.1651 mm |
Tap Drill Size
Recommended tap drill: 17.5 mm
Calculated minor diameter (D₁): 17.29 mm. Closest standard metric drill: 17.5 mm.
Closest inch drill: 11/16" (0.6875" / 17.46 mm)
Proof Loads by Property Class
| Class | Proof Stress (MPa) | Tensile Strength (MPa) | Proof Load (kN) | Tensile Load (kN) |
|---|---|---|---|---|
| 4.6 | 225 | 400 | 54.0 | 95.9 |
| 4.8 | 310 | 420 | 74.3 | 100.7 |
| 5.8 | 380 | 520 | 91.1 | 124.7 |
| 8.8 | 580 | 800 | 139.1 | 191.9 |
| 9.8 | 650 | 900 | 155.9 | 215.8 |
| 10.9 | 830 | 1040 | 199.1 | 249.4 |
| 12.9 | 970 | 1220 | 232.6 | 292.6 |
Proof load = stress area × proof stress. Per ISO 898-1.
Related Thread Sizes
Common Applications
- Structural connections
- Heavy equipment
- Pressure vessels
- Large flanges
How M20×2.5 Dimensions Are Calculated
All dimensions on this page are calculated from ISO 724 formulas using the nominal diameter (20 mm) and pitch (2.5 mm):
- Fundamental triangle height: H = (√3/2) × P = 2.1651 mm
- Pitch diameter: d₂ = d − 0.6495 × P = 18.3762 mm
- Minor diameter (external): d₁ = d − 1.2269 × P = 16.9327 mm
- Minor diameter (internal): D₁ = d − 1.0825 × P = 17.2937 mm
- Thread depth: 5H/8 = 1.3532 mm
- Tensile stress area: Aₛ = (π/4) × ((d₂ + d₃)/2)² = 239.82 mm²