Mushroom Head Square Neck Bolts Carriage Bolt Din 603 Iso 8677 A4-70 8x20 M6 M5 M16 M12 M10x100

A carriage bolt is also called coach bolt or round head square neck bolt or mushroom bolt.

It is distinguished from other bolts by its head: the shank of the bolt is circular for most of its length, as usual, but the portion immediately beneath the head is formed into a square section. This makes the bolt self-locking when placed through a square hole, or a round hole in most wood. This allows the fastener to be installed with only a single tool, a spanner or wrench, working from one side. The head of a carriage bolt is usually a shallow dome. The squared section is of the same size as the diameter of the bolt shank, with a plain unthreaded shank.

Carriage bolts were developed for use through iron strengthening plates on either side of a wooden beam. It is commonplace though to use them into bare timber, the squared section giving enough grip to prevent rotation.

Carriage bolts are mostly used in wood to wood fastening and general construction of decks, porches, swing sets and other home auxiliary units. It comes with a square shoulder and round head which can resist turning when the fastener is being tightened or removed. This ensures that the structure being built is sturdy and robust. The differentiating factor between these bolts and regular bolts is the dome-shaped head - the bolts are not meant to be screwed directly onto surfaces.

These bolts from ITA Fasteners are corrosion resistant because of the stainless steel, alloy steel and carbon steel materials used in its making. The versatility of these bolts allows them to be used on a wide range of applications. They are used for creating wood frames and wood beams and most wood to sheet metal fastening because its unique shape makes this the best contender when it comes to holding wood together. The square shoulder ensures that the structure being built is rigid, by restricting the movement of the materials being joined.