S-8077A643 1/4"-20 ASME B18.3 Shoulder Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance thanks to 316 stainless steel construction with black oxide finish, ideal for harsh environments and extended service life.
• Exceptional mechanical strength with 70,000 psi tensile and 35,000 psi shear strength, ensuring reliable performance under high-stress conditions.
• Precise alignment and secure positioning enabled by the knurled head and standard shoulder fit, reducing assembly time and improving component stability.
• High thread reliability with Class 3A fit and coarse UNC thread, providing consistent engagement and vibration resistance in demanding applications.
• Easy installation and removal using a standard hex drive (3/16"), allowing for efficient maintenance and reducing tooling complexity.
• Compliance with major industry standards including ASME B18.3, RoHS 3, and REACH, ensuring safety, environmental responsibility, and global acceptance.
• Durable wear resistance from Rockwell B79 hardness, maintaining integrity in repetitive motion and high-load scenarios.

Professional Applications & Engineering Value

This shoulder screw is engineered to address critical challenges in precision assemblies, such as misalignment and component wear. The 316 stainless steel material, combined with a black oxide finish, offers excellent protection against corrosion in moist or chemical-rich settings, making it suitable for marine, chemical processing, and food machinery applications. The UNC coarse thread and Class 3A thread fit ensure tight, reliable fastening that resists loosening under vibration, while the knurled head enhances grip during manual adjustments. Its robust shoulder design provides a precise pivot or spacer in rotating parts, reducing friction and extending the lifespan of connected components in automation, robotics, and heavy equipment.

Specification Summary & Compliance

This shoulder screw adheres to tight dimensional tolerances, including a Class 3A thread fit for high precision and a shoulder diameter tolerance of -0.004" to -0.002". It conforms to ASME B18.3 specifications for consistent manufacturing quality and is compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring it is free from hazardous substances and safe for various industrial and international markets.