S-91253A371 1/2"-20 x 3/4" ASTM F835 Alloy Steel Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 130,000 psi ensures reliable performance in high-stress industrial applications, reducing the risk of fastener failure.
• Superior corrosion resistance from the black-oxide finish on alloy steel extends service life in harsh environments, minimizing maintenance needs.
• Precision Class 3A thread fit guarantees tight, secure connections with minimal backlash, enhancing assembly accuracy and vibration resistance.
• Fully threaded design provides consistent clamping force along the entire length, improving load distribution and joint integrity.
• 82° countersink angle and flat head profile allow for flush mounting, creating smooth surfaces and reducing snag hazards in machinery.
• Hex drive (5/16") enables high-torque installation with common tools, speeding up assembly while preventing stripping.
• Compliance with ASME B18.3 and ASTM F835 ensures adherence to rigorous industrial standards, offering peace of mind for quality-critical projects.

Professional Applications & Engineering Value

Engineered for demanding environments, these 1/2"-20 UNF flat head screws in black-oxide alloy steel address common industrial challenges such as vibration loosening and corrosion. The fine thread spacing and Class 3A fit provide superior grip in materials like metals and high-density plastics, reducing the need for frequent retightening in machinery, automotive, and aerospace assemblies. The combination of 130,000 psi tensile strength and Rockwell C39 hardness ensures durability under dynamic loads, while the fully threaded design maximizes engagement in thin-section components. Ideal for applications requiring flush surfaces, the 82° countersink integrates seamlessly, enhancing safety and aesthetics in finished products.

Specification Summary & Compliance

This screw features a 1/2"-20 UNF thread with Class 3A precision tolerance for consistent fit, and is manufactured to ASME B18.3 and ASTM F835 specifications. It complies with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental safety and material restrictions are met for global supply chains.