S-91259A109 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 for reliable performance in high-stress applications
• Precision-engineered shoulder with tight diameter and length tolerances ensures accurate alignment and smooth rotational movement in assemblies
• Superior corrosion resistance through black oxide finish that provides durable protection in demanding industrial environments
• Optimized thread engagement with Class 3A thread fit and UNC coarse threads for secure fastening and vibration resistance
• Enhanced installation control with knurled socket head and hex drive design for secure tool grip and precise torque application
• High material integrity from alloy steel construction with Rockwell C32 hardness for consistent performance and durability
• Regulatory compliance assurance meeting ASME B18.3 specifications and environmental standards including RoHS 3 and REACH

Professional Applications & Engineering Value

This alloy steel shoulder screw delivers critical engineering solutions for precision machinery and industrial equipment where alignment accuracy and rotational stability are paramount. The 2-1/2" shoulder length with controlled tolerances serves as a precise locating diameter for bearings, gears, and rotating components, eliminating the need for additional bushings or spacers. The black oxide finish provides essential corrosion protection while maintaining dimensional stability in harsh operating conditions. With its Class 3A thread fit and UNC coarse threads, this fastener ensures secure attachment while resisting loosening from vibration, making it ideal for automation equipment, precision instruments, and mechanical assemblies requiring reliable shoulder screw performance.

Specification Summary & Compliance

This precision shoulder screw features a 1/4"-20 UNC thread with Class 3A fit for superior engagement, combined with a 2-1/2" shoulder length maintaining tight tolerances (-0.005" to 0.005"). The shoulder diameter of 5/16" is manufactured to precise tolerances (-0.004" to -0.002") for optimal fit. Manufactured from alloy steel with Rockwell C32 hardness, the screw complies with ASME B18.3 specifications and meets environmental standards including RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) compliance requirements.