S-91257A191 5/8"-18 x 4 3/4" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws
High-Strength Grade 8 Steel Hex Head Screws
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Basic Information
Head Parameters
Dimensions
Thread Parameters
Tip & Drive Parameters
Material & Strength
Temperature & Environment
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Key Features & Benefits at a Glance
- Exceptional tensile strength of 150,000 psi ensures reliable performance in high-stress applications, reducing the risk of fastener failure.
- Superior corrosion resistance from zinc yellow-chromate plating extends service life in harsh industrial environments.
- High hardness rating (Rockwell C33) provides excellent wear resistance and durability under heavy loads.
- Precise Class 2A thread fit with UNF fine threading offers secure, vibration-resistant connections in critical assemblies.
- External hex drive design allows for easy installation and high torque application with standard tools.
- Partial threading enables optimal clamping force distribution for enhanced joint stability.
- Compliance with ASME B18.2.1 and SAE J429 standards guarantees consistent quality and interchangeability.
Professional Applications & Engineering Value
These Grade 8 hex head screws deliver critical engineering solutions where failure is not an option. The UNF fine threading with Class 2A fit provides superior resistance to vibrational loosening in heavy machinery, construction equipment, and automotive assemblies. The zinc yellow-chromate plating creates a protective barrier against corrosion in outdoor or chemically aggressive environments, significantly extending maintenance intervals. With 150,000 psi tensile strength and Rockwell C33 hardness, these partially threaded screws maintain structural integrity under extreme dynamic loads, making them ideal for critical connections in structural steelwork, industrial machinery, and transportation equipment where reliability and safety are paramount.
Specification Summary & Compliance
This 5/8"-18 UNF hex head screw features Class 2A thread fit precision and partial threading with minimum thread length of 1½". Manufactured to meet ASME B18.2.1 and SAE J429 Grade 8 specifications, ensuring dimensional accuracy and mechanical properties. The zinc yellow-chromate plating provides corrosion protection while maintaining compliance with industry standards for heavy-duty fasteners in inch measurement system applications.
