S-91257A598 5/16"-18 x 4" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws
High-Strength Grade 8 Steel Hex Head Screws
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Basic Information
Head Parameters
Dimensions
Thread Parameters
Tip & Drive Parameters
Material & Strength
Temperature & Environment
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Key Features & Benefits at a Glance
- Exceptional load-bearing capacity with 150,000 psi tensile strength for reliable performance in high-stress applications
- Superior corrosion resistance through zinc yellow-chromate plating, extending service life in harsh environments
- Optimized torque transmission with external hex drive design for secure installation and removal
- Enhanced thread engagement with UNC coarse threading and Class 2A fit for vibration resistance
- Reduced assembly weight through partial threading while maintaining full strength in critical sections
- Industry-standard compliance meeting ASME B18.2.1 specifications for consistent quality and interchangeability
- Environmental responsibility with RoHS 3 and REACH compliance for sustainable industrial operations
Professional Applications & Engineering Value
These Grade 8 hex head screws deliver critical performance in demanding industrial settings where failure is not an option. The Rockwell C33 hardness combined with 150,000 psi tensile strength ensures reliable fastening in heavy machinery, construction equipment, and structural applications. The zinc yellow-chromate finish provides superior protection against corrosion in outdoor or chemically aggressive environments, while the UNC coarse thread design prevents loosening under vibration. The partially threaded configuration offers optimal clamping force distribution, making these external hex drive fasteners ideal for applications requiring precise joint compression without compromising structural integrity.
Specification Summary & Compliance
Manufactured to exacting Class 2A thread fit tolerances with 5/16"-18 UNC coarse thread specifications. Complies with ASME B18.2.1 standards and SAE J429 Grade 8 requirements for dimensional accuracy and mechanical properties. Meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring safe use across global industrial markets.
