S-91257A420 1/4"-20 x 12" 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
- Superior corrosion resistance through zinc yellow-chromate plating extends service life in harsh environments
- Precise Class 2A thread fit provides consistent engagement and reduces assembly issues
- Heavy-duty Grade 8 rating guarantees maximum durability for industrial applications
- Coarse UNC threading enables faster installation and better performance in softer materials
- External hex drive design allows for high torque application and secure fastening
- Partial threading configuration optimizes clamping force distribution along the shaft
Professional Applications & Engineering Value
This Grade 8 hex head screw delivers critical engineering solutions for heavy machinery, structural assemblies, and industrial equipment where failure is not an option. The combination of 150,000 psi tensile strength and Rockwell C33 hardness ensures these steel fasteners withstand extreme vibrational loads and dynamic stresses. The zinc yellow-chromate plating provides essential corrosion protection in manufacturing environments exposed to moisture and chemicals. With 1/4"-20 UNC coarse threading and partial threading design, these screws offer superior grip in both metal and composite materials, preventing loosening under continuous operation. The external hex drive accommodates standard tools for efficient installation in confined spaces, making them ideal for construction, automotive, and heavy equipment applications requiring reliable, high-strength fastening solutions.
Specification Summary & Compliance
This heavy-duty hex head screw features precise Class 2A thread fit with 1/4"-20 UNC coarse thread specifications and 12-inch length with partial threading. Manufactured to meet ASME B18.2.1 and SAE J429 standards, ensuring dimensional accuracy and performance reliability. The fastener complies with industry standards for Grade 8 strength classification and maintains consistent quality across production batches for engineering applications requiring certified components.
