S-91257A105 1/4"-20 x 4 3/4" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Maximum load-bearing capability with Grade 8 classification and 150,000 psi tensile strength for critical structural applications
• Superior corrosion protection through zinc yellow-chromate plating that withstands harsh industrial environments
• Optimized thread engagement with UNC coarse threading and Class 2A fit ensuring reliable installation and vibration resistance
• Enhanced installation efficiency featuring external hex drive design for high-torque applications and easy wrench access
• Precision manufacturing compliance meeting ASME B18.2.1 and SAE J429 specifications for consistent quality and interchangeability
• Strategic partial threading providing unthreaded shank section for improved shear strength in joint applications
• Exceptional hardness durability with Rockwell C33 rating maintaining fastener integrity under repeated stress cycles

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver critical performance in heavy machinery, structural steel connections, and industrial equipment where failure is not an option. The zinc yellow-chromate plating provides essential corrosion resistance in manufacturing environments exposed to moisture and chemicals, while the UNC coarse threading ensures rapid assembly and superior vibration resistance compared to fine-thread alternatives. The partially threaded design concentrates thread engagement where needed most, preventing stress concentration in the threaded portion and maximizing the screw's clamping force in structural applications. Engineered to ASME B18.2.1 and SAE J429 standards, these fasteners offer predictable performance and reliable interchangeability across industrial maintenance and construction projects.

Specification Summary & Compliance

Manufactured to precise dimensional standards with Class 2A thread fit tolerance for consistent installation performance. The 1/4"-20 UNC coarse thread configuration follows standardized threading specifications, while the 4 3/4" length with 3/4" minimum thread length provides optimal engagement characteristics. Compliant with ASME B18.2.1 dimensional requirements and SAE J429 material and mechanical property specifications, ensuring full traceability and quality assurance for industrial applications. The external hex drive design accommodates standard wrenching tools while maintaining the integrity of the fastener head during high-torque installation.