M6 Carriage Bolts A2-70 Stainless Steel | Round Head Square Neck Coach Screws

A general rule is to select a bolt length equal to the total thickness of the materials being joined, plus at least 1–2 thread pitches beyond the nut face. For example, joining two 15mm boards typically calls for a 35mm (≈1-3/8") bolt. If you're adding a washer and nut, account for that extra 5–8mm. Available lengths run from 25mm (≈1") to 70mm (≈2-3/4").

A2-70 designates austenitic stainless steel with a minimum tensile strength of 700 MPa (≈101,500 psi) per ISO 3506. This is generally sufficient for structural wood connections, outdoor furniture assembly, and light-to-medium load-bearing applications. For heavy structural steel connections, a higher grade may be required.

Yes. A2 stainless steel offers solid corrosion resistance in most outdoor environments including rain, humidity, and mild coastal exposure. For highly aggressive marine or saltwater immersion environments, A4 (316) stainless is typically recommended instead. These bolts are well-suited for decks, pergolas, fences, and garden furniture in standard outdoor conditions.

These bolts use the M6 metric coarse thread (ISO 68-1), with a standard pitch of 1.0mm. They are compatible with any standard M6 hex nut, M6 nylon insert lock nut (Nyloc), and M6 flat or spring washers. They are not compatible with UNC/UNF inch-standard nuts.

The square neck is designed to embed into wood or soft composite material as the nut is tightened, preventing the bolt from rotating. This allows single-person installation — you can tighten the nut from one side without needing to hold the bolt head with a second tool. It also creates a cleaner, snag-free dome head on the visible face of the joint.

For small repairs or single-use projects, a 25-piece box is generally sufficient. For deck building, fencing, or furniture production runs, the 40- or 50-piece boxes offer better value per bolt. All packs ship in a labeled storage box, making it easy to keep leftover fasteners organized for future use.

Yes. A2 stainless steel is generally compatible with ACQ (Alkaline Copper Quaternary) and CA (Copper Azole) pressure-treated lumber, which can rapidly corrode standard zinc-plated or hot-dip galvanized hardware over time. Stainless steel fasteners are typically the recommended choice for treated wood in residential deck and fence construction per IRC guidelines.