S-91251A991 7/8"-9 x 3 1/4" ASTM A574 Alloy Steel Socket Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 170,000 psi ensures reliable performance under extreme loads, reducing the risk of fastener failure in critical applications.
• Black-oxide coating on alloy steel provides superior corrosion resistance and a durable, non-reflective finish for extended service life in harsh environments.
• Class 3A thread fit offers precise, tight-tolerance engagement for secure fastening and vibration resistance in demanding assemblies.
• 3/4" hex drive and standard socket head allow for high-torque installation with common tools, facilitating efficient assembly and maintenance.
• UNRC coarse thread design enables quick installation and superior holding power in a wide range of materials, saving time during production.
• Partially threaded shank provides unthreaded bearing surface for accurate clamping and alignment in structural applications.
• Compliance with ASTM A574 guarantees consistent quality and mechanical properties, ensuring reliability for industrial and engineering uses.

Professional Applications & Engineering Value

These socket head cap screws are engineered to address common industrial challenges such as vibration loosening, high-stress fatigue, and environmental corrosion. The black-oxide alloy steel construction, combined with a Rockwell C37 hardness, ensures durability in heavy machinery, automotive assemblies, and construction equipment where repeated loading and harsh conditions are prevalent. The UNRC coarse thread and Class 3A fit provide secure fastening in metals and composites, minimizing the need for frequent retightening and reducing maintenance downtime. Ideal for use in industrial fasteners requiring high clamp load and reliability, these screws deliver consistent performance in applications demanding maximum strength and longevity.

Specification Summary & Compliance

This product features precise Class 3A thread fit per UNRC standards, with a thread size of 7/8"-9 and a minimum thread length of 2 1/4". It is manufactured in accordance with ASTM A574 specifications, ensuring high tensile strength and dimensional accuracy. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, it meets environmental and safety standards for global industrial use.