S-91257A553 1/4"-20 x 2 3/4" 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 and 150,000 psi tensile strength, ensuring reliable performance in high-stress industrial applications.
• Superior corrosion resistance from the zinc yellow-chromate plating, extending the fastener's lifespan in harsh or outdoor environments.
• Optimized for efficient installation thanks to the external hex drive and coarse UNC threading, which reduce assembly time and prevent cross-threading.
• Enhanced load distribution and stability due to the partially threaded design, minimizing stress concentration on the shank.
• Consistent dimensional accuracy with Class 2A thread fit, providing secure, vibration-resistant connections in machinery and structural assemblies.
• High hardness rating of Rockwell C33 for excellent wear resistance, maintaining thread integrity through repeated use and adjustments.
• Broad regulatory compliance including ASME B18.2.1, SAE J429, RoHS 3, and REACH, ensuring safety and environmental standards are met for global supply chains.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to address critical challenges in heavy-duty and high-vibration environments, such as construction equipment, automotive frames, and industrial machinery. The steel material combined with zinc yellow-chromate plating provides a robust barrier against rust and chemical exposure, significantly reducing maintenance costs and downtime. Its 1/4"-20 UNC coarse thread and partial threading design ensure rapid assembly and superior clamping force, preventing loosening under dynamic loads. By meeting stringent ASME B18.2.1 specifications, these screws deliver consistent performance and interoperability in complex assemblies, making them a trusted choice for engineers prioritizing reliability and compliance.

Specification Summary & Compliance

This fastener adheres to precise dimensional standards, including Class 2A thread fit for consistent engagement and UNC coarse threading with a size of 1/4"-20. It is manufactured in compliance with ASME B18.2.1 and SAE J429 specifications, ensuring mechanical integrity and interchangeability. Additionally, the product is confirmed to be RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, supporting environmentally responsible procurement and use in regulated industries.