M4–M12 Zinc-Plated Cup Square Carriage Bolts with Flange Nuts | 8–150mm

Generally, add the total thickness of all materials being joined, then add at least one full nut height plus a few thread pitches for secure engagement. For example, joining two 10mm (3/8") boards with an M6 bolt typically requires a length of 25–30mm (1"–1-3/16"). When in doubt, size up — a bolt that's slightly too long can be managed with an extra nut or washer, but one that's too short won't clamp properly.

These bolts are typically manufactured to property class 4.8 or 8.8, which generally provides tensile strengths of approximately 400–800 MPa depending on the grade. For load-critical or structural applications, please contact us to confirm the exact property class before ordering.

The zinc electroplating provides moderate corrosion resistance, making these bolts well-suited for indoor use and sheltered outdoor applications such as covered decks, pergolas, and carports. For prolonged direct exposure to rain, salt spray, or standing water, a stainless steel or hot-dip galvanized fastener is generally recommended. Applying a zinc-compatible thread sealant or anti-corrosion compound can extend service life in damp conditions.

These bolts follow the metric coarse thread standard (ISO 68-1 / DIN 603). Standard pitches are: M4 = 0.7mm, M5 = 0.8mm, M6 = 1.0mm, M8 = 1.25mm, M10 = 1.5mm, M12 = 1.75mm. They are fully compatible with any standard metric coarse hex nut or flange nut of the matching diameter, including the flange nuts available as variants in this listing.

A carriage bolt (also called a coach bolt) has a smooth, domed head and a square shank section directly below the head. When inserted into wood or a square-punched hole, the square shank locks the bolt in place so it cannot rotate — allowing you to tighten the nut from one side only with a single wrench. A standard hex bolt has a hex head that requires a wrench on both ends. The smooth dome head of a carriage bolt also eliminates sharp edges, making it safer for furniture and playground equipment.

Yes. The M4, M5, M6, M8, M10, and M12 flange nuts use standard metric coarse threads and are compatible with any metric bolt of the matching diameter and coarse pitch. The integrated flange distributes clamping load over a wider bearing area, reducing the need for a separate flat washer and helping prevent pull-through on softer materials like wood or thin sheet metal.

Packing quantity varies by size and is displayed in the Packing Quantity (Pcs) variant selector. Options include 2, 5, 10, 20, 50, 100, and 200 pieces depending on the bolt diameter and length selected. Flange nuts are sold in packs of 10–200 pieces. Select your preferred quantity before adding to cart.