S-91257A754 1/2"-20 x 4 1/2" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional Tensile Strength – With 150,000 psi tensile strength, this screw reliably handles extreme loads in heavy machinery and structural applications.
• Superior Corrosion Resistance – Zinc yellow-chromate plating provides durable protection against rust and environmental degradation, extending service life.
• High Hardness for Wear Resistance – Rockwell C33 hardness ensures the fastener maintains its integrity under repeated stress and vibration.
• Precise Thread Engagement – Class 2A thread fit and UNF fine thread design offer secure, vibration-resistant connections in critical assemblies.
• Optimized for High-Strength Applications – Grade 8 classification and partial threading provide focused strength where it's needed most, reducing weight without compromising performance.
• Industry-Standard Compliance – Manufactured to ASME B18.2.1 and SAE J429 specifications, ensuring interchangeability and reliability in professional settings.
• Easy Installation with External Hex Drive – Standard 3/4" hex head allows for quick, secure tightening using common tools, improving assembly efficiency.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to solve critical challenges in heavy-duty industrial applications, such as construction equipment, automotive frames, and machinery bases. The 1/2"-20 UNF fine thread and Class 2A thread fit deliver superior resistance to loosening under dynamic loads and vibration, a common failure point in demanding environments. Made from high-strength steel and finished with zinc yellow-chromate plating, it combats corrosion in outdoor or humid conditions, reducing maintenance frequency. The partially threaded design concentrates strength along the shank, making it ideal for connections where clamp load is critical. By meeting ASME B18.2.1 standards, this fastener ensures compatibility and safety in engineered systems, providing peace of mind for engineers and procurement specialists.

Specification Summary & Compliance

This fastener adheres to Class 2A thread tolerance for consistent fit, with UNF fine threads (1/2"-20) and right-hand threading. It conforms to ASME B18.2.1 and SAE J429 specifications for dimensional and mechanical properties. The product is fully RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, ensuring it meets environmental and safety regulations for industrial use worldwide.