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Standard zinc-plated screws corrode fast in coastal air, marine spray, or wet outdoor conditions — and replacing fasteners buried inside a boat fitting or outdoor enclosure is a job nobody wants to repeat. Contractors, marine fabricators, DIY builders, and maintenance professionals who work in corrosive environments need fasteners that hold up long-term without rust staining or structural failure. These M3–M6 truss head Phillips machine screws are manufactured from A4 marine grade 316 stainless steel, the go-to material for saltwater and chemical-exposure applications.
Each screw features a truss head profile — a low-profile, wide-diameter dome head that spreads clamping load over a larger footprint than a standard pan head, reducing pull-through risk in thin sheet metal, plastic panels, and fiberglass without requiring a separate washer. Thread sizes cover M3, M4, M5, and M6 (ISO metric coarse thread), with shank lengths ranging from 4mm (≈5/32") to 60mm (≈2-3/8"). Packs are available in 3, 5, 10, 20, 30, and 50 pieces to suit everything from a single repair to a full production run.
Typical applications include marine hardware and boat deck fittings requiring 316 stainless machine screws, outdoor electrical enclosures and junction boxes in coastal or industrial environments, sheet metal and fiberglass panel assembly where a wide-bearing truss head eliminates the need for a backing washer, and stainless steel furniture or architectural metalwork exposed to rain and humidity.
| Material | 316 Stainless Steel (A4 Marine Grade) |
|---|---|
| Thread Standard | ISO Metric Coarse (DIN 7985 / ISO 7045 profile) |
| Available Thread Sizes | M3, M4, M5, M6 |
| Thread Pitch | M3: 0.5mm | M4: 0.7mm | M5: 0.8mm | M6: 1.0mm |
| Screw Length Range | 4mm (≈5/32") – 60mm (≈2-3/8") |
| Head Type | Truss Head (low-profile wide dome) |
| Drive Type | Phillips (cross point) |
| Property Class | Typically A4-70 — Contact us to confirm |
| Tensile Strength | Typically ≥700 MPa (A4-70) — Contact us to confirm |
| Pack Quantities | 3, 5, 10, 20, 30, 50 pieces |
| Corrosion Resistance | Excellent — suitable for marine and outdoor use |
For truss head screws, the listed length is the total length of the screw including the head. A general rule is to engage at least 1.5× the screw diameter into the receiving material. For example, an M5 screw should typically thread at least 7.5mm into the tapped hole or nut. Available lengths range from 4mm (≈5/32") to 60mm (≈2-3/8") — select based on your material stack-up and required thread engagement.
A4 (316) stainless steel machine screws are generally rated to property class A4-70, with a minimum tensile strength of approximately 700 MPa and a proof load stress of around 450 MPa. For safety-critical or structural applications, please contact us to confirm the exact property class before ordering.
Yes. 316 stainless steel (A4 grade) contains molybdenum, which significantly improves resistance to chloride-induced corrosion compared to 304 (A2) stainless. These screws are well-suited for marine hardware, coastal construction, boat deck fittings, outdoor furniture, and other applications exposed to saltwater, humidity, or chemical environments.
These screws follow the ISO metric coarse thread standard. Thread pitches are: M3 — 0.5mm, M4 — 0.7mm, M5 — 0.8mm, M6 — 1.0mm. They are compatible with standard ISO metric hex nuts, nylon lock nuts, threaded inserts, and tapped holes. Always verify thread pitch compatibility with your specific hardware before assembly.
A truss head is a low-profile, wide-diameter dome head that provides a larger bearing surface than a standard pan head. This distributes clamping load over a wider area, making it ideal for thin or soft materials such as sheet metal, plastic panels, and fiberglass where pull-through resistance is important. It also provides a cleaner, lower-profile appearance compared to a hex bolt with a washer.
These screws use a Phillips (cross) drive. A #1 Phillips screwdriver is generally appropriate for M3–M4, while a #2 Phillips typically fits M5–M6. Using a correctly sized driver reduces the risk of cam-out and head damage. When using a power driver, set the clutch to a low torque setting to avoid over-driving, especially in stainless steel which can be prone to galling.
A2 stainless (304 grade) is suitable for general indoor and mild outdoor use. A4 stainless (316 grade) adds molybdenum to the alloy, providing significantly better resistance to chlorides, salt spray, and acidic environments. For marine, coastal, or chemical exposure applications, A4/316 is the recommended choice. If you're unsure which grade you need, contact us and we can help you select the right fastener.
Packs are available in 3, 5, 10, 20, 30, and 50 pieces. For a single repair or prototype, a 3 or 5-piece pack is typically sufficient. For ongoing marine maintenance, outdoor construction projects, or workshop stock, the 20–50 piece options offer better per-unit value. Contact us if you need quantities larger than 50 pieces.
