M6 M8 Carriage Bolts Steel Zinc Plated – DIN 603 Cup Head Square Neck Screws

Generally, select a bolt length equal to the total thickness of the materials being joined plus enough thread engagement for the nut — typically at least 1× the bolt diameter. For example, joining two 6mm (1/4") boards with an M6 bolt, a 12mm (1/2") or 16mm (5/8") length is typically sufficient. Always measure your stack-up before ordering.

These bolts are manufactured to DIN 603 standards and are generally rated at property class 4.6, which typically provides a tensile strength of around 400 MPa and a yield strength of around 240 MPa. For structural or load-bearing applications, please verify the exact grade with us before ordering.

The zinc plating provides moderate corrosion resistance suitable for indoor and sheltered outdoor use. For prolonged direct exposure to rain, salt spray, or high humidity, a stainless steel or hot-dip galvanized option is generally recommended.

Yes. These bolts use standard ISO metric coarse threads (M6×1.0mm pitch and M8×1.25mm pitch) and are compatible with any standard DIN 934 or ISO 4032 metric hex nuts of the matching size.

The square neck sits directly under the round cup head. When driven into a pre-drilled square hole or soft material like wood, the neck bites in and prevents the bolt from spinning while you tighten the nut from the other side — no wrench needed on the bolt head.

We offer quantities of 1, 5, 10, 20, 50, and 100 pieces per size. For small repairs or prototyping, 1–5 pcs is typically enough. For deck building, fencing, or furniture projects, ordering 20–100 pcs generally offers better per-unit value.

DIN 603 carriage bolts are most commonly used with wood, but they can also be used with thin metal plates when a pre-drilled square hole or a square-hole washer is used to prevent rotation. For heavy steel-to-steel connections, a hex bolt is generally a better choice.