EngiRef / Metric Bolt Specification
M20
M20 coarse-thread metric bolt: 2.5 mm pitch, 20 mm major diameter. Tensile stress area 245 mm² per ISO 898-1. Takes a 30 mm wrench. Free bolt specification…
Specification
- Size
- M20
- Pitch (mm)
- 2.5
- Major diameter d (mm)
- 20
- Minor diameter d₃ (mm, external thread)
- 16.93
- Tensile stress area (mm²)
- 245
- Head height (mm)
- 12.5
- Head diameter (mm)
- 30
- Wrench size (mm)
- 30
Tensile stress area follows ISO 898-1, At = (π/4)(d − 0.9382p)². Verify against the current standard and the fastener manufacturer's data before safety-critical design.