S-91253A578 5/16"-18 x 1/2" ASME B18.3 Alloy Steel Hex Drive Flat Head Screws
Alloy Steel Hex Drive Flat 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
- Superior corrosion resistance with black-oxide coating, extending service life in demanding industrial environments
- Exceptional mechanical strength with 130,000 PSI tensile rating and Rockwell C39 hardness for heavy-duty applications
- Precision Class 3A thread fit ensures secure fastening with minimal risk of cross-threading or loosening
- Optimized 82° countersink angle provides flush mounting in standard countersunk holes
- Hex drive design delivers maximum torque transmission during installation
- Coarse UNC threading enables rapid installation and superior resistance to vibration
- Full threading along entire length allows for maximum adjustability and holding power
Professional Applications & Engineering Value
These black-oxide alloy steel flat head screws are engineered to address critical challenges in industrial assembly where vibration resistance, corrosion protection, and high-strength fastening are paramount. The combination of 5/16"-18 UNC coarse threading with Class 3A precision fit ensures reliable performance in machinery, automotive components, and structural applications where vibration-induced loosening compromises safety. The 82° countersink angle and flat head profile create seamless surface finishes while the hex drive configuration prevents cam-out during high-torque installation. Ideal for OEM manufacturing and maintenance applications requiring RoHS and REACH compliance without sacrificing mechanical performance.
Specification Summary & Compliance
Manufactured to exacting Class 3A thread tolerances with UNC coarse thread form and right-hand threading. Fully compliant with ASME B18.3 dimensional specifications and ASTM F835 mechanical properties. Meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations for industrial use. The black-oxide surface treatment provides additional corrosion protection while maintaining the 130,000 PSI tensile strength and Rockwell C39 hardness of the underlying alloy steel material.
