S-91257A561 1/4"-20 x 5 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 Capacity: With a tensile strength of 150,000 PSI and Grade 8 classification, this screw withstands extreme mechanical stresses, reducing the risk of fastener failure in critical applications.
• Superior Corrosion Protection: Zinc yellow-chromate plating offers enhanced resistance to rust and environmental degradation, extending service life in harsh industrial or outdoor settings.
• Optimized Installation Efficiency: UNC coarse threading and external hex drive enable quick, secure fastening with standard tools, minimizing assembly time and labor costs.
• Exceptional Durability: Rockwell C33 hardness ensures the screw maintains its structural integrity under repetitive loads and vibrations, ideal for heavy machinery and construction.
• Reliable Thread Engagement: Partially threaded design with Class 2A fit provides precise alignment and consistent clamping force, preventing loosening in dynamic environments.
• Broad Industrial Compliance: Meets ASME B18.2.1 and SAE J429 standards, ensuring interchangeability and performance reliability across North American engineering projects.
• Environmental and Safety Assurance: RoHS 3 and REACH compliance guarantees the screw is free from hazardous substances, supporting sustainable and safe workplace practices.

Professional Applications & Engineering Value

Engineered for demanding industrial applications, this Grade 8 hex head screw combines high-strength steel material with a zinc yellow-chromate finish to address common challenges like corrosion in construction, heavy equipment assembly, and infrastructure projects. The UNC coarse thread and external hex drive facilitate rapid installation in high-vibration environments, reducing downtime. With a 1/4"-20 thread size and 5 1/2" length, it provides secure fastening in thick materials, while the partially threaded design ensures optimal grip without compromising joint integrity. Ideal for use in automotive, manufacturing, and structural frameworks, this fastener delivers long-term reliability under 150,000 PSI tensile stress, minimizing maintenance needs and enhancing operational safety.

Specification Summary & Compliance

This screw adheres to precise Class 2A thread fit and UNC coarse threading standards, ensuring dimensional accuracy per ASME B18.2.1 and SAE J429 specifications. It is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its suitability for global markets and environmentally conscious operations.