These carriage bolts are carbon steel with zinc plating for corrosion resistance. The square neck under the round head locks into the mounting hole during installation, preventing the bolt from spinning while tightening the nut. The smooth domed head creates a safe, snag-free surface. Long shank versions are widely used for trailer building, timber connections, farm equipment and heavy frame assembly. Multiple diameters and lengths are in stock.
- Carbon steel with zinc plated anti-rust coating
- Round smooth head + square anti-rotation neck
- No need to hold the bolt while tightening
- Full thread or half thread options available
- Ideal for trailer, timber frame, farm and machinery assembly
- Various sizes in stock, custom lengths supported
Contact us for size chart and bulk quotation.
FAQ
Q: What is zinc plated long carriage bolt round head square neck for trailer assembly used for?
A: This carriage bolt is also called coach bolt. The square neck stops rotation when tightening the nut, widely used to build trailers, connect wooden beams and fix equipment frames.
Q: What is the advantage of the square neck?
A: The square neck embeds into the hole and locks the bolt, so you only need to turn the nut without holding the bolt head.
Q: Can these bolts be used outdoors?
A: Zinc plating offers basic outdoor rust protection. For coastal high-salt environments, hot-dip galvanized versions are recommended.
Q: Do you supply matching nuts and washers?
A: Yes, we can supply matched hex nuts, lock nuts and flat washers together.
Q: Can you make custom long lengths?
A: Yes, we support custom length, thread type and packaging for bulk orders.
