S-91259A108 1/4"-20 ASME B18.3, ASTM A574 Shoulder Screws

Key Features & Benefits at a Glance

• Exceptional Load-Bearing Capacity – With 140,000 psi tensile strength and 84,000 psi shear strength, this shoulder screw provides reliable performance in high-stress applications, reducing the risk of fastener failure.
• Superior Corrosion Resistance – The black oxide finish offers enhanced protection against rust and oxidation, extending service life in demanding industrial environments.
• Precision Thread Fit – Class 3A thread fit ensures tight, secure fastening with minimal backlash, improving assembly accuracy and vibration resistance.
• High Material Hardness – Rockwell C32 hardness provides excellent wear resistance, maintaining dimensional stability under repeated use and mechanical loads.
• Knurled Head for Enhanced Grip – The knurled socket head design allows for secure tool engagement and easier installation, even in confined spaces.
• Industry Standard Compliance – Manufactured to ASME B18.3 and ASTM A574 specifications, ensuring consistent quality, interchangeability, and reliability.
• Environmental and Safety Compliance – RoHS 3 and REACH compliant, making it suitable for use in regulated industries and eco-conscious applications.

Professional Applications & Engineering Value

This 1/4"-20 shoulder screw is engineered to address critical challenges in precision assembly and heavy-duty machinery. The alloy steel construction, combined with a black oxide finish, ensures durability and corrosion resistance in harsh conditions such as automotive, aerospace, and industrial equipment. The UNC coarse thread and Class 3A thread fit provide secure, vibration-resistant fastening, reducing maintenance needs and downtime. The shoulder diameter of 5/16" and length of 2 1/4" allow for precise alignment and rotational support in pivoting mechanisms, bearings, and linkages. Ideal for applications requiring high shear strength and reliable performance, this screw minimizes the risk of loosening and wear, enhancing overall system longevity.

Specification Summary & Compliance

This shoulder screw adheres to ASME B18.3 and ASTM A574 manufacturing standards, ensuring dimensional accuracy and mechanical consistency. Thread specifications include UNC coarse thread with a Class 3A fit for precise engagement. The shoulder diameter tolerance is -0.004" to -0.002", and shoulder length tolerance is -0.005" to 0.005", guaranteeing tight fits in precision assemblies. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its suitability for environmentally sensitive and regulated industrial applications.