M5–M12 Carriage Bolts with Nuts | Cup Square Domed Head | 201 Stainless Steel

Generally, add up the total thickness of all materials being clamped, then add the nut height plus 1–2 thread pitches of extra engagement beyond the nut. For example, joining two 10mm boards with an M8 bolt typically requires at least 25mm (≈1"): 20mm of material + ~5mm nut height. When in doubt, size up one length — a bolt that's slightly long is easier to work with than one that's too short. Lengths on this listing are measured from under the head to the tip.

These bolts follow the ISO metric coarse thread standard (DIN 603 profile). Pitches are: M5 × 0.8mm, M6 × 1.0mm, M8 × 1.25mm, M10 × 1.5mm, M12 × 1.75mm. They are compatible with any standard ISO metric coarse hex nut, lock nut, or flange nut of the matching diameter available at hardware stores.

201 stainless steel provides good corrosion resistance for general outdoor use, including decks, fences, garden furniture, and exterior timber framing exposed to rain and humidity. It is generally not recommended for continuous saltwater immersion or highly corrosive marine environments — for those applications, 316 stainless steel is typically the better choice. For most residential outdoor DIY projects, 201 SS performs well.

201 stainless steel carriage bolts typically have a tensile strength in the range of 500–700 MPa depending on diameter and manufacturing process. They are generally suited for light-to-medium structural connections such as deck railings, furniture joints, and gate hardware. For safety-critical or engineered structural applications, always consult a licensed engineer and verify the specific grade rating. Contact us to confirm specifications if needed.

Directly beneath the domed head is a short square-profile shank section. When the bolt is inserted through a pre-drilled hole in wood or soft material and pulled tight, this square neck bites into the material and locks the bolt rotationally. This means you can tighten the nut from one side without needing to hold the bolt head — ideal for through-bolting applications where the bolt head side is inaccessible or you want a clean, tool-free face.

Yes — each piece in the pack includes one carriage bolt and one matching metric hex nut. The nut is sized and threaded to match the bolt diameter exactly: M5 bolt with M5 nut, M6 with M6, and so on. All nuts follow the same ISO metric coarse thread standard as the bolts, so they are also interchangeable with other standard metric hardware.

Diameters available: M5, M6, M8, M10, M12. Lengths range from 12mm to 100mm. Quick inch conversions: 12mm ≈ 1/2", 16mm ≈ 5/8", 20mm ≈ 3/4", 25mm ≈ 1", 30mm ≈ 1-3/16", 40mm ≈ 1-9/16", 50mm ≈ 2", 60mm ≈ 2-3/8", 80mm ≈ 3-1/8", 100mm ≈ 3-15/16". Pack sizes range from 1 to 50 pieces — select your size and quantity from the variant dropdowns above.