S-90585A055 5/16"-18 x 1 1/8" ASME B18.3 Stainless Steel Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with 316 stainless steel construction, ideal for harsh chemical and marine environments
• Exceptional thread reliability with Class 3A fit ensuring precise engagement and vibration resistance in critical assemblies
• High mechanical strength with 70,000 psi tensile strength and Rockwell B55 hardness for demanding load applications
• Optimized flush mounting with standard 82° countersink angle and flat head design for seamless surface finishing
• Enhanced durability through passivated surface treatment providing extra protection against oxidation and wear
• Efficient installation with hex drive design allowing high-torque application without cam-out risks
• Full thread engagement along the entire 1-1/8" length for maximum grip strength in varied material thicknesses

Professional Applications & Engineering Value

These 316 stainless steel flat head screws deliver critical performance advantages in corrosive and high-stress environments. The combination of UNC coarse threading and Class 3A thread fit provides superior vibration resistance in machinery, industrial equipment, and structural assemblies where loosening under dynamic loads is a concern. The passivated finish significantly enhances the natural corrosion resistance of 316 stainless, making these hex drive screws ideal for chemical processing, marine applications, and food processing equipment where frequent washdowns occur. The 82° countersink angle ensures proper seating in standard chamfered holes, creating flush surfaces that prevent snagging while maintaining structural integrity. These fully threaded fasteners are engineered to solve common challenges in maintenance-heavy industries where durability and reliability are paramount.

Specification Summary & Compliance

Manufactured to ASME B18.3 specifications with Class 3A thread fit tolerance for precision assembly. Features 5/16"-18 UNC coarse threads with right-hand direction and standard flat head profile. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring safe use across global industrial markets. All dimensional tolerances including head diameter (-0.056" to 0") and thread diameter (0.313") meet established industrial standards for consistent performance.