S-91257A939 7/8"-14 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 Rockwell C33 hardness, this screw withstands extreme mechanical stresses, reducing failure risks in critical assemblies.
• Superior Corrosion Resistance: Zinc yellow-chromate plating provides a durable barrier against rust and environmental degradation, extending service life in harsh industrial settings.
• Precise Thread Engagement: UNF fine threads with Class 2A fit ensure tight, secure fastening with minimal risk of cross-threading or loosening under vibration.
• High-Torque Application Ready: The external hex head design (1 5/16" width) allows for easy installation with standard wrenches, enabling efficient assembly in confined spaces.
• Optimized for Heavy-Duty Use: Grade 8 classification and compliance with ASME B18.2.1/SAE J429 standards guarantee consistent performance in demanding mechanical and structural applications.
• Enhanced Durability with Partial Threading: The 2" minimum threaded section on a 4 1/2" length provides focused grip strength where needed, improving resistance to shear and fatigue.
• Environmental and Regulatory Safety: Meets RoHS 3 and REACH compliance, ensuring safe use in regulated industries without hazardous substance concerns.

Professional Applications & Engineering Value

This 7/8"-14 UNF Grade 8 hex head screw is engineered to address common challenges in heavy machinery, construction, and automotive sectors where high tensile strength and corrosion resistance are critical. The zinc yellow-chromate plating combats oxidation in humid or outdoor environments, while the fine thread spacing and Class 2A thread fit ensure reliable clamping force in vibrating equipment. Its partially threaded design concentrates stress on the shank, minimizing thread wear and preventing joint failure. Ideal for bolting structural frames, engine components, or industrial assemblies, this fastener delivers long-term reliability under 150,000 PSI tensile loads, reducing maintenance downtime and enhancing operational safety.

Specification Summary & Compliance

This screw adheres to Class 2A thread fit tolerances for precise alignment and meets ASME B18.2.1 and SAE J429 specifications for dimensional accuracy and mechanical properties. It is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental safety and material sustainability. The UNF thread type with fine spacing and right-hand direction follows standardized industrial practices for compatibility and ease of installation.