S-91257A554 1/4"-20 x 3" 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 150,000 psi tensile strength, ideal for high-stress industrial applications.
• Superior corrosion resistance provided by zinc yellow-chromate plating, extending service life in harsh environments.
• High hardness rating of Rockwell C33 ensures minimal wear and deformation under heavy use.
• Reliable thread engagement with Class 2A UNC coarse threads, enabling quick assembly and reduced cross-threading risk.
• Optimized for high-torque applications thanks to the external hex drive and hex head design.
• Partial threading allows for unthreaded shank strength where maximum clamping force is needed.
• Compliance with major industry standards including ASME B18.2.1, ensuring consistent quality and interchangeability.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to address critical fastening challenges in heavy machinery, construction, and automotive assemblies. The steel material combined with zinc yellow-chromate plating provides a robust barrier against rust and chemical exposure, significantly reducing maintenance frequency. Its 1/4"-20 UNC coarse thread and Class 2A thread fit ensure secure, vibration-resistant connections, even in dynamic load conditions. The partially threaded design concentrates strength in the shank, preventing shear failure. Ideal for high tensile strength requirements, this fastener delivers reliable performance in structural frameworks, engine components, and industrial equipment where failure is not an option.

Specification Summary & Compliance

This screw adheres to ASME B18.2.1 and SAE J429 specifications, with precise Class 2A thread fit for consistent dimensional accuracy. It is fully RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, meeting stringent environmental and safety regulations for industrial use.