Round Low-Profile Head
The smooth domed head provides a clean appearance and reduces external protrusion, making it suitable for applications where exposed fasteners require a neat finish.

ASME B18.5-2 Round Head Square Neck Bolts (Inch Series) are inch-series carriage-style bolts featuring a round head and square neck under the head. The square neck prevents the bolt from rotating during tightening, allowing installation from one side without holding the bolt head. This standard defines dimensional requirements for round head square neck bolts used in general industrial applications.
These bolts are commonly manufactured in materials such as carbon steel, alloy steel, and stainless steel, with mechanical properties and finishes specified according to applicable ASTM, SAE, IFI, and ASME standards.


Standard Compatibility
ASME B18.5-2 defines the dimensional requirements for inch-series round head square neck bolts, ensuring consistency in head size, neck design, and thread compatibility. Standard carriage bolts may follow other specifications depending on region and application.
Application Focus
ASME B18.5-2 bolts are typically selected for engineered applications requiring controlled dimensions, while general carriage bolts are often used for common commercial fastening purposes.
Manufacturing Control
ASME B18.5-2 products provide standardized dimensions suitable for industrial sourcing, OEM production, and replacement applications.
The smooth domed head provides a clean appearance and reduces external protrusion, making it suitable for applications where exposed fasteners require a neat finish.
The square neck grips the mating hole and prevents bolt rotation during installation, improving tightening efficiency and reducing the need for additional tools.
It is an inch-series bolt with a rounded head and square neck designed to prevent rotation during tightening. It is part of the ASME B18.5 round head bolt family.
The square neck locks into a square hole or formed material surface, preventing the bolt from spinning while the nut is tightened.
They are frequently used in industrial equipment, agricultural machinery, construction applications, and assemblies requiring a tamper-resistant smooth head design.
Yes. Manufacturers can provide customized materials, coatings, lengths, thread specifications, and packaging according to project requirements.



