Guardrail bolts are the fasteners that hold a W-beam crash barrier together. The head is domed and smooth so nothing projects into the traffic face, and the neck is oval so it locks into the slot in the rail and cannot spin while the nut is tightened from behind. Both features are set by the road, not by the fastener — which is why a guardrail bolt is a specification item and not a generic carriage bolt.
Two types. Splice bolts join one rail panel to the next and are normally 5/8 × 1¼ in (M16 × 32 mm), eight per splice. Post bolts pass through the rail, the blockout and the post, and run from 2 to 46 in (50 to 1,170 mm).
Specification. Geometry and thread to AASHTO M180. Material ASTM A307 Grade A, 60 ksi (414 MPa) minimum tensile. Thread 5/8-11 UNC-2A, or M16 × 2 to the metric edition. Hot-dip galvanized to ASTM A153 Class C or F2329, with the recessed nut tapped oversize so it still runs on the coated thread.
Supplied with matching recessed nuts and washers, plate washers manufactured at our Umm Al Quwain plant, and an EN 10204 3.1 certificate traceable to the heat.
Full dimensions, chemical and mechanical data and an animation of the bolt fitting the rail: see our guardrail bolt technical page.
