S-91257A428 1/4"-28 x 7 1/2" 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 Grade 8 screw withstands extreme loads, reducing the risk of fastener failure in high-stress environments.
• Superior Corrosion Resistance – The zinc yellow-chromate plating provides a durable barrier against rust and corrosion, extending service life in harsh industrial conditions.
• Precise Fastening with Fine Threads – The UNF fine thread design offers better adjustment and vibration resistance, ensuring a secure, tight fit in critical assemblies.
• High Hardness for Durability – Rockwell C33 hardness ensures the screw maintains its shape and strength under repeated use, minimizing wear and deformation.
• Reliable Thread Fit – Class 2A thread fit guarantees consistent, easy assembly with standard nuts, improving installation efficiency and reducing cross-threading risks.
• Heavy-Duty Hex Head Design – The external hex drive and 7/16" head width allow for high torque application, enabling quick and secure fastening with common tools.
• Industry Standard Compliance – Manufactured to ASME B18.2.1 and SAE J429 specifications, ensuring interoperability and reliability in professional applications.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered for demanding industrial settings where failure is not an option. The steel construction and 150,000 psi tensile strength address common challenges like dynamic loads and vibration, providing a robust solution for heavy machinery, structural frameworks, and automotive assemblies. The zinc yellow-chromate finish combats corrosion in outdoor or humid environments, while the UNF fine thread enhances grip in materials prone to loosening. Partially threaded design allows for controlled clamping force, making it ideal for applications requiring precise joint integrity. By meeting ASME B18.2.1 standards, this fastener ensures consistent performance in industrial screws and heavy-duty bolting systems, reducing maintenance downtime and enhancing operational safety.

Specification Summary & Compliance

This fastener adheres to critical specifications: Thread Fit Class 2A for precise dimensional accuracy, UNF fine thread with 1/4"-28 size, and a minimum thread length of 1". It complies with ASME B18.2.1 and SAE J429 standards, ensuring manufacturing consistency and reliability. The zinc yellow-chromate plating meets RoHS and REACH environmental directives, providing a safe, corrosion-resistant finish. With a length of 7 1/2" and Grade 8 strength classification, it is suitable for high-performance applications requiring verified mechanical properties and industry-recognized quality assurance.