S-91257A421 1/4"-28 x 5" 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 150,000 psi tensile strength and Grade 8 classification, ensuring reliable performance in high-stress industrial environments.
• Superior corrosion protection through zinc yellow-chromate plating, extending service life in harsh or outdoor conditions.
• Precise thread engagement with UNF fine threads and Class 2A fit, reducing the risk of cross-threading and providing secure fastening.
• Enhanced durability from Rockwell C33 hardness, resisting wear and deformation under heavy loads.
• Optimized for high-torque applications with an external hex drive and hex head design, allowing for easy installation with standard tools.
• Versatile partial threading enabling unthreaded shank sections to bear shear loads effectively in structural assemblies.
• Compliance with industry standards including ASME B18.2.1 and SAE J429, guaranteeing interchangeability and quality assurance.

Professional Applications & Engineering Value

Engineered for demanding industrial applications, this Grade 8 hex head screw addresses critical challenges in machinery, construction, and heavy equipment assembly. The steel construction combined with zinc yellow-chromate plating provides a robust barrier against rust and chemical exposure, essential in environments with moisture or corrosive agents. Its UNF fine thread design ensures tighter sealing and vibration resistance, minimizing loosening in dynamic systems. The partially threaded configuration allows the unthreaded portion to act as a precision dowel, absorbing shear forces in bolted joints. By meeting ASME B18.2.1 specifications, it offers reliable dimensional consistency for replacement and OEM use, reducing downtime and maintenance costs in high-tensile strength scenarios.

Specification Summary & Compliance

This fastener adheres to Class 2A thread fit tolerances for consistent engagement and is manufactured in accordance with ASME B18.2.1 and SAE J429 standards. Key specifications include a 1/4"-28 UNF fine thread, 5" length with a minimum threaded portion of 3/4", and external hex drive compatibility. The product conforms to industry-recognized metrics for Grade 8 strength and material integrity, ensuring compliance with common engineering and procurement requirements.