S-91255A558 1/4"-28 x 7/8" ASTM F835 Steel Button Head Hex-Drive Screws
Steel Button Head Hex-Drive 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 harsh industrial environments.
- Exceptional tensile strength of 120,000 psi ensures reliable performance under high-stress applications.
- Precision Class 3A thread fit guarantees secure, vibration-resistant connections with minimal risk of loosening.
- High hardness (Rockwell C39) provides excellent wear resistance and durability for repeated use.
- 5/32" hex drive design allows for easy installation and removal with standard tools, improving assembly efficiency.
- Fully threaded UNF fine spacing offers superior grip and load distribution in demanding assemblies.
- Compliance with ASME B18.3 and ASTM F835 ensures consistent quality and interchangeability in regulated industries.
Professional Applications & Engineering Value
This 1/4"-28 UNF black-oxide alloy steel rounded head screw is engineered to address critical challenges in precision assemblies where vibration resistance, corrosion protection, and high tensile strength are paramount. The Class 3A thread fit and fine thread spacing minimize backlash and enhance joint integrity in machinery, automotive, and aerospace applications. Its rounded button head and 5/32" hex drive facilitate smooth, low-profile installations without compromising torque transmission. The black-oxide finish not only provides a durable barrier against oxidation but also reduces galling, making these screws ideal for repetitive disassembly and maintenance cycles in corrosive or high-humidity settings.
Specification Summary & Compliance
This screw adheres to Class 3A thread tolerance per UNF standards, with a 1/4"-28 thread size and 7/8" length. It meets ASME B18.3 and ASTM F835 specifications for dimensional accuracy and mechanical properties. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental safety and regulatory acceptance in global markets.
