S-91266A560 1/4"-28 x 1/2" ASTM F835 Alloy Steel Thread-Locking Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Vibration-resistant performance with permanent nylon patch thread locker that maintains secure fastening in high-stress environments
• Superior corrosion protection through black-oxide coating on alloy steel, extending service life in demanding industrial conditions
• Precise flush mounting with standard 82° countersink angle and flat head design for seamless surface integration
• Exceptional mechanical strength delivering 130,000 psi tensile strength and Rockwell C39 hardness for heavy-duty applications
• Reliable temperature tolerance maintaining locking integrity across a wide operating range from -65° to 250°F
• Premium threading accuracy with Class 3A UNF fine threads ensuring precise fit and consistent clamping force
• Easy installation and removal using standard 5/32" hex drive for efficient assembly and maintenance procedures

Professional Applications & Engineering Value

These nylon patch locking flat head screws provide critical vibration resistance in machinery, automotive, and aerospace assemblies where loosening under dynamic loads poses significant reliability concerns. The black-oxide alloy steel construction combined with Class 3A UNF fine threading ensures superior corrosion resistance and precise fit in tight-tolerance applications. The permanent thread locker patch eliminates the need for secondary locking compounds while maintaining performance across extreme temperature variations from -65° to 250°F. The 82° countersink angle and flat head profile enable flush mounting in precision equipment where surface protrusions are unacceptable, making these fully threaded screws ideal for critical joints in manufacturing equipment, electronic enclosures, and structural frameworks requiring dependable, maintenance-free fastening solutions.

Specification Summary & Compliance

Manufactured to exact Class 3A thread fit standards with 1/4"-28 UNF fine threading and complete compliance with ASTM F835 specifications. These screws meet RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring safe use in global industrial markets. The fully threaded design with right-hand thread direction provides consistent engagement throughout the fastener length, while the standardized 82° countersink angle guarantees proper seating in corresponding chamfered holes.