S-91257A833 5/8"-18 x 5" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 150,000 psi ensures reliable performance in high-stress applications, preventing fastener failure under heavy loads.
• Superior corrosion resistance from zinc yellow-chromate plating protects against rust and environmental degradation, extending service life in harsh conditions.
• Precision Class 2A thread fit guarantees smooth assembly and secure fastening, reducing the risk of cross-threading and improving installation efficiency.
• High hardness (Rockwell C33) provides excellent wear resistance, maintaining thread integrity and fastener shape through repeated use.
• Partially threaded design allows for controlled clamping force and secure grip on materials, ideal for applications requiring precise joint compression.
• External hex drive and hex head enable easy installation with standard tools, offering high torque capability and reducing slippage during tightening.
• Compliance with industry standards including ASME B18.2.1 and SAE J429 ensures consistent quality, reliability, and interchangeability in industrial assemblies.

Professional Applications & Engineering Value

This 5/8"-18 UNF Grade 8 hex head screw is engineered to address critical challenges in heavy-duty industrial environments, such as structural steel connections, machinery assembly, and automotive systems. The fine thread spacing and Class 2A thread fit provide enhanced vibration resistance and secure fastening in dynamic applications, reducing maintenance needs. Made from high-strength steel and finished with zinc yellow-chromate plating, it combats corrosion in outdoor or chemically exposed settings, ensuring long-term durability. The partially threaded design concentrates clamping force where needed, preventing joint loosening and improving load distribution. Ideal for construction, manufacturing, and equipment repair, this fastener delivers reliable performance under extreme mechanical stress while meeting rigorous ASME B18.2.1 and SAE J429 specifications.

Specification Summary & Compliance

This screw features a 5/8"-18 UNF thread with Class 2A tolerance for precise fit, a 5" length, and partial threading with a minimum thread length of 1 1/2". It adheres to ASME B18.2.1 and SAE J429 standards for dimensional accuracy and performance. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, it ensures environmental safety and material restrictions are met for industrial use.