DIN 603 Stainless Steel Carriage Bolt Round Head Square Neck

Compliant with DIN 603 international standards, this carriage bolt is crafted from premium 304/316 stainless steel, offering exceptional corrosion resistance, rust proofing, and durability—ideal for indoor, outdoor, and humid environments. Featuring a classic round head and integral square neck design, it prevents bolt rotation during installation: the square neck locks into pre-drilled holes (wood, metal, or plastic substrates), allowing easy tightening from the nut side without extra tools. Available in both full thread (for maximum grip in thick materials) and partial thread (for better load distribution in thin substrates) options, it caters to diverse fastening needs.

It is distinguished from other bolts by its shallow mushroom head and the fact that the cross-section of the shank, though circular for most of its length (as in other kinds of bolt), is square immediately beneath the head. This makes the bolt self-locking when it is placed through a square hole in a metal strap. This allows the fastener to be installed with only one wrench, working from the opposite end. The head of a carriage bolt is usually a shallow dome. The shank has no threads and its diameter equals the size of the square cross-section.

The carriage bolt was devised for use through an iron strengthening plate on either side of a wooden beam, the squared part of the bolt fitting into a square hole in the ironwork. It is common to use a carriage bolt on bare timber, the square section giving enough grip to prevent rotation.

The carriage bolt is used extensively in security applications, such as locks and hinges, where the bolt must be removable from one side only. The smooth, domed head and square nut below prevent the carriage bolt from being gripped and rotated from the insecure side.