S-91266A577 5/16"-18 x 1/2" ASTM F835 Alloy Steel Thread-Locking Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Vibration-resistant locking with nylon patch thread locker that maintains secure fastening in temperatures from -65° to 250°F
• Superior corrosion protection through black-oxide coating on alloy steel, extending service life in demanding environments
• Precise thread engagement with Class 3A fit ensuring reliable installation and consistent clamping force
• Exceptional mechanical strength delivering 130,000 psi tensile strength and Rockwell C39 hardness for heavy-duty applications
• Optimized drive efficiency with 3/16" hex drive providing positive torque transmission and reduced cam-out risk
• Full-thread design offering maximum thread engagement along the entire 1/2" length for enhanced load distribution
• Industry compliance assurance meeting ASTM F835 specifications while being RoHS 3 and REACH compliant

Professional Applications & Engineering Value

These 5/16"-18 UNC flat head screws with nylon patch thread locker provide critical vibration resistance in industrial machinery, automotive assemblies, and electrical enclosures where thermal cycling and dynamic loads compromise joint integrity. The black-oxide alloy steel construction combines corrosion resistance with the high tensile strength needed for structural applications, while the Class 3A thread fit ensures precise installation without galling or cross-threading. The 82° countersink angle creates flush mounting in standard chamfered holes, making these fully threaded screws ideal for applications requiring consistent clamping force across the entire fastener length. Engineered to maintain performance under extreme conditions, these screws prevent costly downtime through reliable vibration-resistant fastening.

Specification Summary & Compliance

Manufactured to exacting UNC coarse thread specifications with Class 3A thread fit for superior dimensional accuracy. These flat head screws comply with ASTM F835 standards for mechanical properties and performance. The product meets RoHS 3 (2015/863/EU) compliance for hazardous substance restrictions and REACH (EC 1907/2006) requirements for chemical safety. The right-hand threading and standard flat head profile ensure compatibility with industry-standard installations and tools.