S-91263A503 4-40 x 1/2" ASTM F835 Alloy Steel Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with zinc plating, extending service life in demanding industrial environments
• Exceptional tensile strength of 130,000 psi ensures reliable, vibration-resistant fastening under high-stress conditions
• Precision Class 3A thread fit provides consistent, secure engagement and reduces cross-threading risks
• 82° countersink angle allows for flush mounting in standard countersunk holes, improving aesthetics and safety
• Full threading along the 1/2" length maximizes grip and load distribution across the entire fastener
• High Rockwell C39 hardness enhances wear resistance and maintains thread integrity during repeated use
• Hex drive design (1/16") enables easy installation and removal with standard tools, reducing assembly time

Professional Applications & Engineering Value

These 4-40 UNC flat head screws are engineered from zinc-plated alloy steel to address critical industrial fastening challenges, such as vibration loosening and environmental corrosion. The coarse thread spacing and Class 3A thread fit ensure rapid, secure installation in materials where fine threads might strip, making them ideal for assembly lines and machinery requiring consistent, high-volume fastening. The 82° flat head profile sits flush with surfaces, eliminating protrusions in automotive, aerospace, and electronics enclosures. With full threading and right-hand direction, they provide uniform clamping force, reducing the risk of joint failure in dynamic load applications. Compliant with ASTM F835, these screws deliver reliable performance in harsh conditions while meeting stringent industry standards for safety and durability.

Specification Summary & Compliance

These screws feature a 4-40 UNC thread size with Class 3A thread fit for precise dimensional accuracy, ensuring compatibility with standard nuts and tapped holes. Manufacturing adheres to ASTM F835 specifications, guaranteeing consistent quality and performance. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming the absence of restricted hazardous substances and supporting environmentally responsible sourcing for global industrial supply chains.