S-91205A112 4-40 x 3/4" ASME B18.3, ASTM A574 Alloy Steel Thread-Locking Socket Head Screws

Key Features & Benefits at a Glance

• Vibration-resistant secure fastening with permanent Nylon Patch thread locker that maintains integrity from -70° to 250°F, preventing loosening in dynamic environments.
• Exceptional tensile strength and durability from alloy steel construction, rated at 170,000 psi and Rockwell C37 hardness for high-stress applications.
• Precise thread engagement and reliability with Class 3A UNC coarse threads, ensuring consistent fit and reduced risk of cross-threading.
• Corrosion-resistant black-oxide finish enhances longevity and provides a professional appearance in demanding industrial settings.
• Compact, high-torque installation capability via 3/32" hex drive and standard socket head, ideal for confined spaces with standard tools.
• Full-threaded design for maximum grip along the entire 3/4" length, offering versatile fastening depth and uniform load distribution.
• Compliance with major industrial standards including ASME B18.3 and ASTM A574, guaranteeing interchangeability and quality assurance.

Professional Applications & Engineering Value

This 4-40 UNC Socket Head Cap Screw is engineered to address critical challenges in machinery, automotive, and electronics assembly where vibration and thermal cycling compromise fastener integrity. The Black-Oxide Alloy Steel construction resists corrosion while the Nylon Patch thread locker provides a permanent locking mechanism without requiring secondary adhesives, streamlining production. Its Class 3A thread fit and coarse UNC thread form enable quick installation and high clamp force retention in metals and composites, reducing maintenance downtime. Ideal for motor mounts, enclosures, and precision equipment, this screw delivers reliable performance under cyclic loads and temperature extremes from -70° to 250°F, ensuring long-term operational safety.

Specification Summary & Compliance

This screw adheres to ASME B18.3 dimensional standards and ASTM A574 material specifications, with precise Class 3A thread fit for superior tolerance control. The UNC coarse thread (4-40 size) and fully threaded 3/4" length ensure consistent performance. It is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming the absence of restricted substances for global industrial use.