S-91257A828 5/8"-18 x 3 1/2" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional load-bearing capacity with a tensile strength of 150,000 PSI, ideal for high-stress industrial environments.
• Superior corrosion resistance provided by zinc yellow-chromate plating, extending service life in harsh conditions.
• Reliable thread engagement with UNF fine threading and Class 2A fit, ensuring precise, vibration-resistant connections.
• High hardness rating of Rockwell C33, offering excellent wear resistance and durability under repetitive use.
• Optimized for heavy-duty torque application through an external hex drive and hex head design, facilitating easy installation with standard tools.
• Partial threading allows for controlled clamping force, making it suitable for applications requiring specific unthreaded shank sections.
• Compliance with major industry standards including ASME B18.2.1 and SAE J429, guaranteeing consistent quality and performance.

Professional Applications & Engineering Value

Engineered for demanding industrial settings, this Grade 8 hex head screw addresses critical challenges in heavy machinery, construction, and automotive assemblies. The steel material and UNF fine thread design provide superior resistance to loosening under vibration, a common issue in dynamic load applications. The zinc yellow-chromate finish not only enhances corrosion protection but also maintains integrity in outdoor or chemically exposed environments. With a 3 1/2" length and partial threading, it offers versatility for components requiring high clamp load without full thread engagement, reducing stress concentration. This fastener is ideal for structural frames, engine components, and equipment where high tensile strength and reliability are non-negotiable, ensuring long-term operational safety and reducing maintenance frequency.

Specification Summary & Compliance

This product adheres to precise dimensional tolerances, including a Class 2A thread fit for consistent assembly. It conforms to ASME B18.2.1 and SAE J429 specifications, ensuring interoperability and performance reliability. Additionally, it is RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, meeting environmental and safety regulations for hazardous substances.