S-91257A730 1/2"-13 x 4 1/2" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Maximum Load-Bearing Capability – With a tensile strength of 150,000 psi and Grade 8 classification, this screw withstands extreme mechanical stresses in heavy machinery and structural applications.
• Superior Corrosion Resistance – Zinc yellow-chromate plating provides a durable barrier against rust and environmental degradation, extending service life in harsh conditions.
• Optimized Thread Engagement – UNC coarse thread spacing with Class 2A fit ensures quick, secure installation and reliable vibration resistance in industrial assemblies.
• Enhanced Durability – Rockwell C33 hardness offers excellent wear resistance and maintains fastener integrity under repeated loading.
• Efficient Installation & Removal – External hex drive and standard 3/4" head width allow for high-torque application using common tools, reducing assembly time.
• Partial Threading Design – Combines a fully threaded section for grip with an unthreaded shank for shear strength, ideal for dynamic load applications.
• Regulatory Compliance – Meets ASME B18.2.1, SAE J429, RoHS 3, and REACH standards, ensuring safety and environmental responsibility in global supply chains.

Professional Applications & Engineering Value

Engineered for heavy-duty industrial fastening, this Grade 8 hex head screw addresses critical challenges in construction, machinery, and structural frameworks. The 1/2"-13 UNC coarse thread with Class 2A fit provides superior holding power in high-vibration environments, preventing loosening in equipment and steel connections. Zinc yellow-chromate plating delivers reliable corrosion protection, making it suitable for outdoor or chemically exposed settings. With 150,000 psi tensile strength and a partially threaded design, it effectively distributes stress, reducing the risk of fatigue failure in dynamic applications like vehicle chassis, industrial conveyors, and building supports. This combination of material strength, precise thread spacing, and protective finish ensures long-term performance and reduced maintenance costs.

Specification Summary & Compliance

This fastener adheres to Class 2A thread fit and UNC coarse thread spacing per ASME B18.2.1 and SAE J429 specifications. It is manufactured from high-strength steel with a zinc yellow-chromate plated finish and complies with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring it meets international safety and sustainability standards for industrial use.