EngiRef / UNC Bolt Specification
#4-40
#4-40 coarse UNC bolt: 40 threads per inch, 2.84 mm major diameter. Tensile stress area 3.89 mm² per ASME B1.1. Takes a 5.56 mm wrench. Free imperial fastener…
Specification
- Size
- #4-40
- Threads per inch (TPI)
- 40
- Major diameter D (mm)
- 2.84
- Minor diameter D₁ (mm, internal thread)
- 2.01
- Tensile stress area (mm²)
- 3.89
- Wrench size (mm)
- 5.56
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.