Brass fasteners are a copper-zinc alloy valued for corrosion resistance, electrical conductivity, non-sparking properties, and appearance. They are significantly weaker than steel — tensile strength is typically 360–500 MPa depending on alloy and temper, with proof stresses around 120–200 MPa.
Brass bolts have no standardized property class system like ISO 898-1 or SAE J429. Torque values must be calculated from the specific alloy's mechanical properties, and are generally 25–35% of the torque for an equivalent-size steel 8.8 bolt.
| Size | N·m | ft·lbs | vs Steel 8.8 |
|---|---|---|---|
| M4 | 0.7 | 0.5 | ~28% |
| M5 | 1.4 | 1.0 | ~28% |
| M6 | 2.5 | 1.8 | ~27% |
| M8 | 6.0 | 4.4 | ~24% |
| M10 | 12 | 8.9 | ~24% |
| M12 | 21 | 15.5 | ~24% |
Assumes proof stress ~150 MPa, K = 0.20 dry. Lubrication strongly recommended.
Marine and plumbing: Excellent resistance to saltwater and dezincification (in naval brass alloys). Standard for through-hull fittings and seawater valve bonnet bolts.
Electrical: High conductivity makes brass ideal for grounding connections and electrical terminal bolts. Never substitute steel — the resistance difference matters.
Hazardous environments: Brass is non-sparking, making it mandatory in explosive atmospheres (petrochemical, grain handling, munitions). Use only brass or bronze tools and fasteners where spark ignition is a risk.
Decorative: Architectural hardware, furniture, and instrument fittings where appearance matters.