S-91253A312 1/4"-28 x 1 1/8" ASTM F835 Alloy Steel Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with black-oxide coating on alloy steel, extending service life in demanding industrial environments
• Exceptional load-bearing capability with 130,000 psi tensile strength and Rockwell C39 hardness for heavy-duty applications
• Precision thread engagement through Class 3A fit and UNF fine threading, ensuring vibration resistance and secure fastening
• Efficient installation and removal with 5/32" hex drive design, reducing assembly time and tool slippage risks
• Flush surface finishing achieved through 82° countersink angle and standard flat head profile for streamlined assemblies
• Full-threaded design providing consistent clamping force along the entire 1-1/8" length for uniform stress distribution
• Regulatory compliance assurance meeting ASTM F835, RoHS 3, and REACH standards for global industrial applications

Professional Applications & Engineering Value

Engineered for high-stress industrial assemblies, these 1/4"-28 UNF flat head screws address critical challenges in machinery, automotive, and equipment manufacturing. The black-oxide alloy steel construction provides enhanced corrosion protection where environmental factors threaten fastener integrity. With Class 3A thread fit and UNF fine threading, these screws maintain clamp load under vibration, preventing loosening in dynamic applications. The hex drive configuration delivers superior torque transmission compared to slotted drives, while the 82° countersink enables seamless integration into precision-machined components. These fully threaded fasteners ensure maximum thread engagement in thick materials, making them ideal for structural applications requiring 130,000 psi tensile strength and reliable performance in demanding operating conditions.

Specification Summary & Compliance

Manufactured to precision inch system dimensions with Class 3A thread fit tolerance and UNF (Unified National Fine) thread standard. Complies with ASTM F835 specification for alloy steel hex drive screws and maintains full compliance with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations. The black-oxide surface treatment provides additional corrosion protection while maintaining dimensional accuracy across all critical parameters including head diameter, drive size, and thread specifications.