S-91253A323 1/4"-28 x 2 3/4" ASTM F835 Alloy Steel Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Exceptional Tensile Strength – Withstands up to 130,000 psi, ensuring reliable performance in high-stress industrial environments.
• Precision Thread Fit – Class 3A thread tolerance provides superior engagement and vibration resistance in critical assemblies.
• Enhanced Corrosion Resistance – Black-oxide coating on alloy steel offers durable protection against rust and wear.
• Optimized Head Design – Flat head with 82° countersink angle allows for flush mounting, reducing snagging and improving aesthetics.
• Secure Hex Drive – 5/32" hex drive enables high-torque installation without cam-out, speeding up assembly processes.
• Fine Thread Spacing – UNF fine threads deliver better adjustment control and holding power in precision applications.
• Partial Threading – Allows for focused clamping force where needed, minimizing material stress and thread damage.

Professional Applications & Engineering Value

These 1/4"-28 UNF flat head screws are engineered to address common challenges in machinery, automotive, and structural assemblies where vibration loosening and corrosion are concerns. The black-oxide alloy steel construction, combined with a Rockwell C39 hardness, ensures long-term durability under dynamic loads. The hex drive and fine thread spacing facilitate precise installation in tight spaces, reducing the risk of stripping and improving repeatability in production lines. Ideal for industrial fastening applications requiring flush surfaces and high tensile strength, these screws help minimize maintenance downtime and enhance operational safety.

Specification Summary & Compliance

Manufactured to ASTM F835 specifications, these screws feature a Class 3A thread fit for precise dimensional accuracy and a right-hand UNF thread type. They are fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental safety and material traceability. The inch system measurements and 82° countersink angle adhere to industry standards for compatibility with existing tooling and components.