S-91257A563 1/4"-20 x 6 1/2" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional strength and durability with Grade 8 classification, 150,000 psi tensile strength, and Rockwell C33 hardness for reliable performance in the most demanding applications.
• Superior corrosion resistance provided by the zinc yellow-chromate plating, extending the fastener's service life in harsh or outdoor environments.
• Optimized for high-torque assembly thanks to the external hex head design, allowing for secure installation with standard tools.
• Reliable and fast engagement from the UNC coarse thread and Class 2A fit, reducing cross-threading risks and speeding up installation.
• Versatile partial threading offers an unthreaded shank for precise clamping in structural and machinery applications.
• Guaranteed compliance and interchangeability by meeting ASME B18.2.1 and SAE J429 standards, ensuring consistent quality and fit.
• Ideal for heavy-load scenarios with a substantial 6-1/2" length and 1/4"-20 thread size, providing a robust solution for thick materials.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to solve critical challenges in heavy-duty industrial and construction applications. The high-strength steel construction, combined with a Rockwell C33 hardness and 150,000 psi tensile strength, ensures it can withstand extreme vibrational loads and high stress without failing. The zinc yellow-chromate plating provides a robust barrier against corrosion, making it suitable for outdoor machinery, agricultural equipment, and structural frameworks exposed to the elements. Its UNC coarse thread and Class 2A fit allow for quick, secure fastening in steel-to-steel connections, reducing assembly time while minimizing the risk of thread stripping. The partially threaded design ensures that the unthreaded shank bears the shear load effectively, providing superior clamping force in pulley systems, brackets, and heavy machinery where joint integrity is paramount.

Specification Summary & Compliance

This fastener features a 1/4"-20 UNC coarse thread with a Class 2A thread fit for standard tolerance and easy assembly. It is manufactured to meet ASME B18.2.1 and SAE J429 specifications, ensuring dimensional accuracy and mechanical properties. The screw is partially threaded with a minimum thread length of 1 inch and a total length of 6-1/2 inches. The zinc yellow-chromate finish complies with common industry requirements for corrosion protection. This product conforms to RoHS and REACH environmental regulations, making it suitable for global industrial supply chains.