S-91251A516 5-40 x 2 1/2" ASTM A574 Alloy Steel Socket Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 170,000 psi ensures reliable performance in high-stress applications, reducing the risk of fastener failure.
• Precision Class 3A thread fit provides superior engagement and vibration resistance, minimizing loosening in dynamic environments.
• Black-oxide coating on alloy steel offers enhanced corrosion resistance, extending service life in harsh industrial conditions.
• Partially threaded design allows for precise clamping force control and secure fastening in specific assembly requirements.
• Hex socket drive enables high-torque installation with standard tools, improving assembly efficiency and reducing strip-out risks.
• Rockwell C37 hardness ensures excellent wear resistance and durability under repetitive loading conditions.
• Coarse UNC threads facilitate quicker installation and better performance in materials prone to stripping or cross-threading.

Professional Applications & Engineering Value

These 5-40 UNC Socket Head Cap Screws deliver critical engineering advantages in demanding industrial applications. The black-oxide alloy steel construction provides superior corrosion resistance compared to standard finishes, making them ideal for machinery, automotive components, and equipment exposed to moisture or chemicals. The Class 3A thread fit ensures precise tolerance control, eliminating play in precision assemblies while the partially threaded configuration allows engineers to designate exact clamping zones. With 170,000 psi tensile strength and Rockwell C37 hardness, these screws maintain integrity under extreme vibration and load conditions commonly encountered in manufacturing equipment, aerospace components, and heavy machinery. The hex socket drive design accommodates high torque applications where space constraints prevent conventional wrench access.

Specification Summary & Compliance

Manufactured to exacting inch system dimensions with Class 3A thread fit per UNC standards, ensuring precise mechanical engagement. These screws meet ASTM A574 specification for alloy steel socket head cap screws and maintain compliance with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations. The coarse thread spacing and partial threading provide optimal performance in various materials while the black-oxide surface treatment enhances corrosion protection without compromising dimensional accuracy.