S-93791A408 4-40 x 5/16" ASME B18.3 Stainless Steel Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Exceptional corrosion resistance with 18-8 stainless steel construction and black-oxide passivated finish, ideal for harsh industrial environments.
• Superior mechanical strength offering 70,000 psi tensile strength and Rockwell B55 hardness for reliable, long-term performance under high stress.
• Precise Class 3A thread fit ensures tight, secure fastening with minimal risk of loosening in critical assemblies.
• Optimized for flush mounting with an 82° countersink angle and standard flat head profile, providing a smooth, unobtrusive finish.
• Easy installation and removal using a 1/16" hex drive, reducing assembly time and tool wear.
• Full threading along the 5/16" length maximizes grip and load distribution across the entire fastener.
• Compliance with major standards including ASME B18.3, RoHS 3, and REACH, ensuring safety and regulatory acceptance in global markets.

Professional Applications & Engineering Value

These 4-40 UNC flat head screws are engineered to address common challenges in precision machinery, electronics, and automotive assemblies where space constraints and corrosion are concerns. The 18-8 stainless steel base material, enhanced by a black-oxide passivated finish, provides excellent resistance to oxidation and chemical exposure, extending service life in demanding conditions. The Class 3A thread fit and coarse UNC threading ensure rapid, secure installation with high vibration resistance, reducing maintenance needs. Ideal for applications requiring flush mounting, such as panel fastening or enclosure systems, the 82° countersink angle and flat head design prevent protrusion, safeguarding against snagging and improving aesthetic integration. With full threading and a hex drive, these screws offer consistent clamping force and ease of use in automated or manual assembly lines, supporting efficient production workflows.

Specification Summary & Compliance

This product adheres to precise dimensional and performance criteria, including a Class 3A thread fit per UNC standards for tight tolerance fastening. It meets ASME B18.3 specifications for flat head screws, ensuring interoperability and reliability. The manufacturing process complies with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming the absence of hazardous substances and supporting environmental and safety standards in industrial supply chains.