Hex Bolts A325

Hex bolts a325, also known as heavy hex structural bolts or high strength structural bolts, are designed to be used in steel-to-steel structural connections. A325 bolts have a heavy pattern head to increase the bearing surface and distribute the load over a larger area. They are typically short in length, as they need to be tightened close to their proof strength to create significant bolt tension. The bolts are made of medium carbon or carbon boron steel that is quenched and tempered to develop their mechanical properties. These bolts may be specified as type 1, type 2, or type 3 depending on the requirements of the project.

The original hex bolts a325 specification was withdrawn in 2016 and replaced by ASTM F3125, but this article will cover technical aspects of the original ASTM standard until the new microsite is up. NHF offers A325 bolts in sizes from 1/2” through 1-1/2”, with threaded lengths up to four times their diameter. Bolts longer than this will need to be custom manufactured to meet the required specification.

A325 bolts are often specified in connection with ASTM A490 nut threads and washers. These fasteners are available in a variety of finish options, including hot-dipped galvanized. This type of coating protects the bolt from corrosion and provides additional protection for the structure to which it is attached. Many industry standards and codes require the use of bolts that are traceable and controlled. This helps ensure that all bolts in a particular lot of bolts have met certain quality standards and can be traced back to their source for quick recalls or replacement when issues are discovered.

These bolts have a maximum tensile strength of 830 MPa and a minimum yield strength of 660 MPa. They are a special class of bolts that can be manufactured to various head configurations and threaded lengths, varying from standard hex bolts to full hex. They can be heat treated to achieve a rockwell hardness of C24-38, allowing them to hold a high level of strength and durability for long periods of time.

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By:Ningbo Hope Fasteners Co., Ltd.