S-91257A815 5/8"-11 x 4 1/4" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional Tensile Strength – With a 150,000 psi rating, this screw withstands extreme loads, reducing the risk of failure in demanding applications.
• Superior Corrosion Resistance – The zinc yellow-chromate plating provides a durable barrier against rust and environmental degradation, extending service life.
• High Hardness for Durability – Rockwell C33 hardness ensures the screw maintains its shape and thread integrity under high stress and repeated use.
• Reliable Fastening with Coarse Threads – UNC coarse threading allows for quick installation and secure holding power, even in softer materials or dirty conditions.
• Optimized for Heavy-Duty Use – Partially threaded design and Grade 8 classification make it ideal for structural and machinery applications requiring high clamp force.
• Precision Thread Fit – Class 2A thread fit ensures consistent engagement and ease of assembly, minimizing cross-threading and improving installation efficiency.
• External Hex Drive for High Torque – The hex head design enables easy application of high torque with standard tools, speeding up assembly in industrial settings.

Professional Applications & Engineering Value

Engineered for heavy-duty industrial applications, this Grade 8 hex head screw addresses critical challenges in construction, machinery, and structural assemblies where high tensile strength and corrosion resistance are paramount. The zinc yellow-chromate plated steel construction combats harsh environments, preventing fastener degradation and maintenance downtime. With UNC coarse threads and a partially threaded shank, it provides optimal grip and load distribution, reducing vibration loosening in equipment and frameworks. Ideal for use in bolted connections requiring compliance with ASME B18.2.1 and SAE J429 standards, it ensures reliability in automotive, manufacturing, and infrastructure projects, delivering long-term performance and safety.

Specification Summary & Compliance

This screw features precise Class 2A thread fit and UNC coarse threading with a thread size of 5/8"-11, ensuring dimensional accuracy per industry standards. It complies with ASME B18.2.1 and SAE J429 specifications, guaranteeing consistent quality and performance. The manufacturing adheres to strict tolerances for length (4 1/4"), thread diameter (0.625"), and material properties, with no specified RoHS or REACH data provided. Designed for reliability in heavy-duty applications, it meets the requirements for high-strength fastening in various industrial sectors.