⚓ Marine Grade 316 Stainless Steel Hex Head Lag Screws – Built for Saltwater & Coastal Wood
If you’ve ever watched standard lag bolts turn into rusty messes on a dock or beachside deck, you know the frustration. These 316 stainless steel hex head lag screws are different. Made from A4 marine grade stainless (316), they resist pitting and corrosion even in direct salt spray. Whether you’re fastening boat dock planks, building a seawall, or securing timber on a coastal pergola, these DIN571 wood lag bolts give you the holding power of a hex head with the peace of mind that comes from true rustproof performance. Available in a wide range of lengths and diameters (2mm to 8mm thread sizes, 4mm to 200mm lengths) – pick what fits your project.
✨ Why Upgrade to A4 Marine Grade Wood Lag Bolts?
🔩 Genuine 316 stainless (A4-70) – The gold standard for corrosion resistance. Outlasts 304 in saltwater, chlorine, and acidic environments.
🌊 Saltwater resistant & rustproof – Perfect for marinas, docks, piers, and any outdoor wood project near the ocean.
⚙️ Heavy duty hex head – Allows maximum torque with a wrench or socket; no cam-out like Phillips drives.
📏 DIN571 coarse thread with sharp point – Bites into hardwood and softwood alike; self-tapping in many woods.
✨ Premium polished finish – Sleek, high-gloss surface that looks clean and resists surface staining.
📦 Wide size range – Thread sizes from 2mm to 8mm, lengths from 4mm up to 200mm. Find exactly what your build needs.
📏 Technical Specifications – 316 Marine Grade Lag Screws
| Type |
Hexagon Head Coach Screws / Wood Lag Bolts |
| Material |
316 Stainless Steel (A4-70 Marine Grade) |
| Standard |
DIN 571 |
| Grade |
A4 (superior to A2/304 for saltwater) |
| Head Style |
Hexagon |
| Thread Type |
Coarse, deep threads with sharp point |
| Finish |
Premium polished, high-gloss untreated |
| System of Measurement |
Metric |
| Screw Sizes (Thread / Diameter) |
2mm, 3mm, 4mm, 5mm, 6mm, 8mm |
| Item Lengths Available |
4mm, 8mm, 10mm, 20mm, 30mm, 40mm, 50mm, 60mm, 75mm, 100mm, 150mm, 200mm |
| Brand / MPN |
Unbranded / Does Not Apply |
❓ Frequently Asked Questions – Marine Grade Hex Head Lag Bolts
🌊 What’s the real difference between 304 and 316 stainless steel for lag screws?
304 (A2) is fine for indoor or mild outdoor use. But 316 (A4) contains molybdenum, which dramatically improves resistance to chlorides – like saltwater, pool chemicals, and coastal fog. If your project is within a mile of the ocean or on a boat, 316 is the only smart choice. These marine grade wood lag bolts won’t pit or rust after one season.
🔧 Do I need to pre-drill before driving these hex head lag screws into wood?
For softwoods like cedar or pine, the sharp point and coarse thread often allow self-tapping. For hardwoods (iroko, teak, oak) or near the edge of any board, always drill a pilot hole about 80-90% of the screw diameter. Example: for a 6mm lag screw, use a 5mm or 5.5mm pilot bit. This prevents splitting and makes driving much easier.
⚓ Can I use these A4 lag bolts for dock or boat trailer repairs?
Absolutely. That’s exactly what these are made for. The A4 rustproof composition is ideal for constant wet environments, including freshwater and saltwater docks, boat lifts, and even submerged wood applications. For trailer repairs above water line, they’re also perfect – just avoid using them below the waterline on aluminum trailers (different metals can cause galvanic corrosion).
📏 How do I choose the right length and thread size for my project?
General rule: the screw should penetrate at least 1.5 times the thickness of the top material into the base wood. For example, if attaching a 2x4 (1.5” thick), select a lag bolt length that gives you 2-2.5” of bite. Thread size (diameter) depends on load – 8mm is heavy duty, 4-5mm is fine for furniture or light framing. We list both screw size and length separately so you can mix and match.
🧲 Will these marine grade lag bolts rust if I scratch the surface?
No. Unlike coated steel or zinc-plated hardware, 316 stainless is solid alloy throughout. A scratch won’t expose a different metal; the entire screw remains corrosion-resistant. However, if you embed it in pressure-treated wood with high copper content (ACQ), 316 is still the recommended choice – it holds up much better than 304.
