S-91253A305 1/4"-28 x 5/8" ASTM F835 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 that protects against rust and extends service life in harsh industrial environments
- Exceptional tensile strength of 130,000 PSI ensures reliable performance under high-stress applications without fastener failure
- Precision Class 3A thread fit provides tighter tolerances for secure, vibration-resistant connections in critical assemblies
- Optimized 82° countersink angle allows for flush mounting in standard countersunk holes, reducing protrusion and improving aesthetics
- Hex drive design enables high-torque installation with standard tools, preventing cam-out and ensuring efficient assembly
- Full threading along the 5/8" length maximizes grip strength and load distribution across the entire fastener
- Fine UNF thread spacing delivers enhanced clamping force and superior resistance to loosening in dynamic applications
Professional Applications & Engineering Value
These black-oxide alloy steel flat head screws with 1/4"-28 UNF fine threads are engineered to address critical fastening challenges in industrial machinery, automotive systems, and precision equipment. The Class 3A thread fit ensures minimal backlash and superior vibration resistance, preventing costly downtime in high-cycle applications. The combination of 130,000 PSI tensile strength and Rockwell C39 hardness provides exceptional durability against shear and tensile loads, while the black-oxide surface treatment offers reliable corrosion protection without compromising dimensional accuracy. The hex drive configuration allows for secure tool engagement during high-torque installation, making these fully threaded screws ideal for applications requiring flush mounting and reliable performance in demanding environments.
Specification Summary & Compliance
Manufactured to ASME B18.3 and ASTM F835 specifications with Class 3A thread fit and UNF fine thread spacing. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental standards. Features include 82° countersink angle, 5/8" length, and right-hand thread direction.
