S-90251A169 4-40 x 1/4" ASME B18.3 Set Screws

Key Features & Benefits at a Glance

• Permanent vibration resistance with nylon patch thread locker that maintains consistent locking performance even under thermal cycling from -50° to 250°F
• Superior corrosion resistance in harsh environments thanks to 316 stainless steel construction with Rockwell B80 hardness
• Precise thread engagement with Class 3A fit UNC coarse threads ensuring reliable fastening and reduced cross-threading risk
• Secure installation and removal through hex drive design with 0.050" drive size providing positive torque transmission
• Concentrated holding force from cup tip design that bites into mating surfaces for maximum grip
• Space-saving headless design allowing flush mounting in confined spaces and rotating assemblies
• Right-hand thread configuration for standard installation procedures and compatibility with common equipment

Professional Applications & Engineering Value

This 4-40 UNC nylon patch locking set screw delivers critical vibration resistance in demanding industrial applications where loosening under dynamic loads poses significant safety and performance risks. The 316 stainless steel construction provides exceptional corrosion resistance in chemical processing, marine, and food processing environments, while the nylon patch locking technology maintains consistent clamping force across a wide temperature range from -50° to 250°F. The Class 3A thread fit with UNC coarse threads ensures precise engagement in precision assemblies, reducing the risk of cross-threading during installation. The combination of cup tip design and hex drive allows for concentrated holding power and reliable torque application in shaft collars, gears, and pulleys where permanent positioning is required.

Specification Summary & Compliance

This set screw features precision 4-40 UNC coarse threads with Class 3A fit for superior dimensional accuracy and reliable fastening performance. Manufactured in compliance with ASME B18.3 standards for set screw dimensional requirements. The product is RoHS 3 (2015/863/EU) compliant and REACH (EC 1907/2006) compliant, meeting current environmental regulations for industrial components. The nylon patch thread locker maintains effectiveness across the specified temperature range of -50° to 250°F, ensuring consistent locking performance in various operating conditions.