S-91266A539 1/4"-20 x 5/8" ASTM F835 Alloy Steel Thread-Locking Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Secure vibration-resistant locking with nylon patch thread locker that maintains integrity across a wide temperature range from -65° to 250°F
• Exceptional tensile strength rated at 130,000 psi ensures reliable performance in demanding industrial applications
• Precise Class 3A thread fit provides superior engagement and reduces the risk of cross-threading during installation
• Corrosion-resistant black-oxide finish on alloy steel extends service life in challenging environments
• Optimized flat head design with 82° countersink angle allows for flush mounting in various materials
• Hex drive compatibility with 5/32" drive size enables efficient installation with standard tools
• Full threading along the 5/8" length ensures maximum grip strength throughout the fastener engagement

Professional Applications & Engineering Value

These black-oxide alloy steel flat head screws with nylon patch thread locking technology address critical industrial fastening challenges where vibration resistance and thermal stability are paramount. The UNC coarse thread configuration combined with Class 3A precision threading ensures rapid installation and superior holding power in metals, plastics, and composite materials. Engineered for machinery, equipment assembly, and structural applications, these fully threaded screws provide reliable performance where loosening under dynamic loads could compromise safety. The 82° countersink angle facilitates seamless integration with standard chamfered holes, while the hex drive design allows for high-torque installation without cam-out issues common in Phillips drives.

Specification Summary & Compliance

Manufactured to exacting ASTM F835 specifications with Class 3A thread fit tolerance for precision engagement. These 1/4"-20 UNC coarse thread screws feature fully threaded design with right-hand thread direction. Compliance includes RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring they meet current industry standards for hazardous substance restrictions and chemical safety protocols.