EngiRef / UNC Bolt Specification
1-8
1-8 coarse UNC bolt: 8 threads per inch, 25.4 mm major diameter. Tensile stress area 391 mm² per ASME B1.1. Takes a 38.1 mm wrench. Free imperial fastener…
Specification
- Size
- 1-8
- Threads per inch (TPI)
- 8
- Major diameter D (mm)
- 25.4
- Minor diameter D₁ (mm, internal thread)
- 21.97
- Tensile stress area (mm²)
- 391
- Wrench size (mm)
- 38.1
Tensile stress area follows ASME B1.1, At = 0.7854(D − 0.9743/n)² in², converted at 645.16 mm²/in². Verify against the current standard and the fastener manufacturer's data before safety-critical design.