S-91273A586 1/4"-28 Shoulder Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with 18-8 stainless steel construction, ideal for harsh industrial environments and extended service life.
• Enhanced durability and wear resistance provided by the black oxide finish, reducing galling and offering a sleek, protective layer.
• Precise alignment and smooth rotation ensured by the Class 2A thread fit and standard shoulder fit, minimizing assembly play and vibration loosening.
• High mechanical strength with 70,000 psi tensile and 35,000 psi shear strength, reliably handling significant loads in demanding applications.
• Secure and easy installation using the 1/8" hex socket drive and knurled head, providing excellent grip and torque transmission without stripping.
• Accurate positioning due to the fine 1/4"-28 UNF threading and consistent 3/4" shoulder length, ensuring repeatable performance in assemblies.
• Compliance with global standards including RoHS 3 and REACH, making it suitable for international markets and regulated industries.

Professional Applications & Engineering Value

This 1/4"-28 UNF shoulder screw is engineered to address critical alignment and pivot point requirements in machinery and equipment. The 18-8 stainless steel material offers excellent resistance to rust and corrosion, which is vital in humid or chemically aggressive settings like food processing, marine, or outdoor applications. The black oxide finish not only enhances the aesthetic but also reduces friction during installation, preventing seizing. With a 3/4" shoulder length and Class 2A thread fit, it provides a precise unthreaded bearing surface that supports rotating components such as gears, pulleys, and linkages, minimizing wear and maintaining concentricity. The fine thread and socket head design allow for compact installations in tight spaces, making it a reliable choice for precision assemblies in automation, automotive, and aerospace engineering.

Specification Summary & Compliance

This shoulder screw adheres to UNF thread standards with a Class 2A thread fit for consistent, precise engagement. The shoulder diameter tolerance is -0.004" to -0.002", and shoulder length tolerance is -0.005" to 0.005", ensuring high dimensional accuracy. Manufactured from 18-8 stainless steel with a Rockwell B55 hardness, it meets mechanical performance criteria. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its suitability for environmentally conscious and regulated industrial applications.