S-91257A840 5/8"-18 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 load-bearing capability with 150,000 psi tensile strength for reliable performance in high-stress environments
• Superior corrosion resistance provided by zinc yellow-chromate plating, extending service life in demanding conditions
• Optimized torque transmission through the external hex drive design for secure installation and removal
• Precise thread engagement with UNF fine threads and Class 2A fit ensuring vibration resistance and consistent clamping force
• Enhanced durability from Rockwell C33 hardness that maintains structural integrity under repeated stress
• Versatile partial threading allowing both secure fastening and adjustable positioning in assembly applications
• Industry compliance assurance meeting ASME B18.2.1 and SAE J429 specifications for quality and interoperability

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver critical engineering solutions for heavy-duty industrial applications where failure is not an option. The combination of high-strength steel construction and UNF fine threading provides superior resistance to vibrational loosening in machinery, construction equipment, and automotive assemblies. The zinc yellow-chromate plating creates a protective barrier against corrosive elements in outdoor or harsh environment applications, while the external hex drive enables high-torque installation without stripping. The partially threaded design offers precise clamping control in structural connections, making these industrial hex bolts ideal for critical joints requiring both strength and adjustability in manufacturing and maintenance operations.

Specification Summary & Compliance

Manufactured to exacting standards with Class 2A thread fit tolerance for consistent performance, these fasteners feature 5/8"-18 UNF fine threads and comply with ASME B18.2.1 dimensional requirements and SAE J429 material specifications. The 4 1/4" length with 1 1/2" minimum thread length provides optimal engagement characteristics. These components meet industry standards for heavy-duty fastening applications and are manufactured in compliance with RoHS and REACH environmental regulations.