S-91255A555 1/4"-28 x 5/8" ASTM F835 Steel Button Head Hex-Drive Screws

Key Features & Benefits at a Glance

• Exceptional corrosion resistance with black-oxide coating, extending service life in harsh industrial environments.
• Superior thread engagement and vibration resistance due to Class 3A fit and UNF fine threading, ensuring reliable, long-term fastening integrity.
• High tensile strength of 120,000 psi and Rockwell C39 hardness for demanding applications requiring robust mechanical performance.
• Easy installation and removal with a 5/32" hex drive, providing secure tool grip and reducing assembly time.
• Fully threaded design offers consistent clamping force along the entire 5/8" length for uniform load distribution.
• Compliance with major industry standards including ASME B18.3 and ASTM F835, guaranteeing quality and interoperability.
• Environmentally responsible manufacturing with RoHS 3 and REACH compliance, meeting global regulatory requirements for safe use.

Professional Applications & Engineering Value

This black-oxide alloy steel rounded head hex screw is engineered to address critical challenges in precision assembly, such as loosening under vibration and corrosion in exposed conditions. The UNF fine thread with Class 3A fit ensures tight tolerances, minimizing the risk of cross-threading and providing excellent fatigue resistance in dynamic loads. Ideal for machinery, automotive, and electronics enclosures, its button head profile offers a low-profile, flush finish that reduces snagging while the alloy steel core delivers consistent strength. By combining high tensile strength with fine threading, it solves issues of joint integrity in applications where space is constrained and reliability is non-negotiable.

Specification Summary & Compliance

This screw adheres to Class 3A thread fit for precise dimensional accuracy, with UNF fine spacing (1/4"-28) and full threading along the 5/8" length. Manufactured in compliance with ASME B18.3 and ASTM F835 specifications, it meets rigorous mechanical and quality standards. Additionally, it is RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, ensuring environmental safety and regulatory acceptance in industrial markets.