S-91259A121 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 shoulder fit ensures accurate alignment and smooth rotation in assemblies, reducing wear and maintenance
• Corrosion-resistant black oxide finish provides durable protection against rust in demanding industrial environments
• Knurled socket head design offers superior grip and prevents tool slippage during installation
• Class 3A thread fit delivers tight tolerances and secure fastening in critical applications
• 4" shoulder length accommodates various component thicknesses for versatile design applications
• Industry compliance meets ASME B18.3 specifications and environmental regulations including RoHS 3 and REACH

Professional Applications & Engineering Value

This alloy steel shoulder screw delivers exceptional engineering value in precision mechanical systems where alignment and rotational accuracy are critical. The 4" shoulder length provides stable bearing surfaces for gears, pulleys, and rotating components, eliminating the need for additional bushings or spacers. The black oxide finish protects against corrosion in industrial environments while maintaining dimensional stability. With its UNC coarse thread and Class 3A fit, this socket head shoulder screw ensures secure fastening in high-vibration applications common in machinery, automation equipment, and precision instruments. The knurled head texture combined with hex drive design prevents cam-out during torque application, making installation and maintenance more efficient in confined spaces.

Specification Summary & Compliance

This shoulder screw features precision 1/4"-20 UNC coarse threads with Class 3A fit for tight tolerance applications. The shoulder maintains a diameter of 5/16" with tolerance of -0.004" to -0.002" and length of 4" with tolerance of -0.005" to 0.005". Manufactured from alloy steel with Rockwell C32 hardness, the screw complies with ASME B18.3 specifications where identified as ASTM A574. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations.