S-91327A285 4-40 ASME B18.3 Shoulder Screws

Key Features & Benefits at a Glance

• Superior vibration resistance with a permanent Nylon patch thread locker, maintaining secure fastening from -50° to 250°F in demanding environments.
• Exceptional durability and corrosion resistance thanks to 18-8 stainless steel construction and passivated finish, ideal for harsh industrial settings.
• High tensile strength of 70,000 psi and Rockwell B55 hardness ensure reliable performance under heavy loads without stripping or shearing.
• Precise alignment and smooth rotation with a 1/8" shoulder diameter and 3/4" shoulder length, minimizing component wear and misalignment.
• Accurate and secure threading with Class 3A UNC coarse threads, providing a tight fit and easy installation in right-hand applications.
• Easy installation and removal using a standard 5/64" hex drive socket head, reducing assembly time and tooling requirements.
• Compliance with industry standards including ASME B18.3, RoHS 3, and REACH, ensuring safety and environmental responsibility.

Professional Applications & Engineering Value

This 4-40 UNC thread shoulder screw is engineered to address critical challenges in precision machinery, such as maintaining alignment in rotating assemblies and resisting loosening under continuous vibration. The 18-8 stainless steel material, combined with a passivated finish, offers excellent resistance to corrosion and wear, extending service life in automotive, aerospace, and electronic enclosures. The integrated Nylon patch locking feature ensures that the screw remains securely fastened without the need for additional adhesives, simplifying maintenance. Its Class 3A thread fit and precise shoulder dimensions (1/8" diameter and 3/4" length) enable exact positioning in bearing mounts and linkage systems, reducing downtime and improving operational reliability. This makes it an ideal choice for high-stress applications where vibration resistance and dimensional accuracy are paramount.

Specification Summary & Compliance

This shoulder screw features a Class 3A thread fit with UNC coarse threads, ensuring high precision and interchangeability. Key dimensions include a shoulder diameter of 1/8" (tolerance: -0.004" to -0.002") and shoulder length of 3/4" (tolerance: -0.005" to 0.005"), manufactured to ASME B18.3 specifications. It is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its adherence to environmental and safety standards for industrial use.