S-91266A085 2-56 x 1/4" ASTM F835 Alloy Steel Thread-Locking Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Vibration-resistant performance with nylon patch thread locker that maintains integrity from -65° to 250°F
• Superior corrosion protection through black-oxide coating on alloy steel for extended service life
• Precise installation control with hex drive design ensuring secure torque application
• Reliable thread engagement achieved through Class 3A fit for minimal backlash in critical assemblies
• High-load capacity with 130,000 psi tensile strength supporting demanding mechanical applications
• Optimized flush mounting featuring 82° countersink angle for seamless surface integration
• Full-thread engagement along the 1/4" length providing maximum holding power

Professional Applications & Engineering Value

These 2-56 UNC flat head screws deliver critical vibration resistance in industrial equipment, electronics enclosures, and precision machinery where loosening under dynamic loads compromises safety. The black-oxide alloy steel construction combined with Class 3A thread fit ensures dimensional stability in high-cycle applications, while the nylon patch thread locker eliminates the need for secondary locking components. The hex drive configuration enables precise installation in confined spaces, and the 82° countersink maintains aerodynamic surfaces in transportation and aerospace assemblies. Engineered for coarse thread applications requiring rapid assembly, these fully threaded fasteners provide uniform stress distribution across the entire engagement length.

Specification Summary & Compliance

Manufactured to ASTM F835 specifications with Class 3A thread fit precision and UNC coarse threading. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental standards. Features 130,000 psi tensile strength and Rockwell C39 hardness with fully threaded 1/4" length and standardized 82° countersink angle.