S-91257A556 1/4"-20 x 3 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 Grade 8 steel construction and 150,000 psi tensile strength for critical structural applications
• Superior corrosion protection through zinc yellow-chromate plating that withstands harsh industrial environments
• Optimized thread engagement with UNC coarse threading and Class 2A fit ensuring reliable fastening in various materials
• Enhanced installation efficiency featuring external hex drive design for secure tool engagement and torque application
• Partial threading design providing unthreaded shank strength where maximum clamping force is required
• Industry-standard compliance meeting ASME B18.2.1 specifications for dimensional accuracy and performance reliability
• Environmental responsibility with RoHS 3 and REACH compliance for sustainable manufacturing practices

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver exceptional engineering value in demanding industrial applications where failure is not an option. The high-strength steel construction combined with Rockwell C33 hardness provides superior resistance to vibration loosening and shear forces in heavy machinery, structural steel connections, and equipment manufacturing. The zinc yellow-chromate plating offers enhanced corrosion protection, making these 1/4"-20 UNC threaded fasteners ideal for outdoor construction, automotive assemblies, and industrial equipment exposed to moisture and chemicals. The partially threaded design ensures maximum clamping force distribution while the external hex drive allows for high-torque installation in confined spaces. These heavy-duty screws solve critical fastening challenges in applications requiring both exceptional tensile strength and long-term corrosion resistance.

Specification Summary & Compliance

This 3-1/2" hex head screw features precise 1/4"-20 UNC coarse threading with Class 2A thread fit for optimal engagement and dimensional accuracy. Manufactured to ASME B18.2.1 specifications and SAE J429 Grade 8 standards, ensuring consistent performance and interchangeability. The fastener is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, confirming adherence to the latest substance restriction requirements for industrial applications worldwide.