S-91571A409 1/2"-13 x 5 1/2" ASME B18.2.6, ASTM A325, ASTM F3125 Medium-Strength Steel Heavy Hex Head Screws for Structural Applications

Key Features & Benefits at a Glance

• Exceptional Structural Integrity: Grade A325 classification and 120,000 psi tensile strength ensure reliable performance in high-stress applications, preventing joint failure under heavy loads.
• Superior Durability & Wear Resistance: Rockwell C19 hardness provides excellent resistance to deformation and wear, extending service life in demanding industrial environments.
• Optimized Load Distribution: 4½" grip length and partial threading design concentrate clamping force where needed most, enhancing connection stability in structural assemblies.
• Secure Fastening with Standard Tools: 7/8" external hex head allows for high-torque installation using common wrenches, reducing installation time and improving worksite efficiency.
• Reliable Thread Engagement: 1/2"-13 UNC coarse threads provide superior resistance to vibration loosening while enabling quicker installation compared to fine-thread alternatives.
• Regulatory Compliance Assurance: Meets ASME B18.2.6, ASTM A325, and ASTM F3125 specifications, ensuring consistent quality and performance in regulated applications.
• Environmental Responsibility: RoHS 3 and REACH compliance demonstrates commitment to sustainable manufacturing practices without compromising performance standards.

Professional Applications & Engineering Value

These Grade A325 hex head screws deliver critical engineering solutions for structural steel connections, heavy machinery assembly, and construction applications where failure is not an option. The steel construction with precise Class 2A thread fit ensures consistent installation torque values and reliable clamp load development. The partially threaded design with substantial 4½" grip length concentrates the tensile strength exactly where structural loads are transferred, preventing thread stripping in connection plates. The 1/2"-13 UNC coarse threading provides superior performance in vibration-prone environments while the external hex drive accommodates high-torque applications common in bridge construction, building frameworks, and industrial equipment manufacturing. These fasteners solve critical challenges in heavy-duty applications by combining verified material properties with standardized dimensions that engineering specifications require.

Specification Summary & Compliance

Manufactured to exacting inch system dimensions with Class 2A thread fit tolerance for consistent installation performance. Complies with ASME B18.2.6 dimensional specifications, ASTM A325 material requirements, and ASTM F3125 testing protocols. Meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental compliance standards. The right-hand UNC coarse threads with 0.5" diameter and 1" thread length provide standardized engagement characteristics across compatible applications.