S-91770A108 4-40 x 3/8" ASME B18.6.3 Stainless Steel Truss Head Phillips Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with passivated 18-8 stainless steel construction, ideal for harsh environments and extended service life
• Enhanced load distribution through the wide truss head design, reducing surface damage and preventing pull-through in softer materials
• High tensile strength of 70,000 psi ensures reliable fastening under significant mechanical stress and vibration
• Optimized drive engagement with Phillips No. 1 drive style, providing secure torque application and reducing cam-out risks
• Precision threading with Class 2A fit guarantees consistent engagement and easy assembly in coarse UNC thread applications
• Full threading along the 3/8" length allows for maximum adjustability and holding power across various material thicknesses
• Compliance with ASME B18.6.3 and environmental regulations ensures product reliability and safe use in regulated industries

Professional Applications & Engineering Value

These 4-40 UNC rounded truss head screws deliver critical performance in demanding industrial settings where corrosion resistance and mechanical integrity are paramount. The passivated 18-8 stainless steel material effectively combats oxidation and chemical exposure, making these fasteners suitable for outdoor equipment, marine components, and food processing machinery. The wide truss head distributes clamping force over a larger area, minimizing the risk of material deformation in sheet metal, plastics, and electronic enclosures. Combined with a coarse thread spacing and Class 2A fit, they provide quick installation and reliable retention in assemblies subject to vibration. Engineers value the fully threaded design for versatile grip range and the Phillips drive for efficient manual or automated driving, streamlining production while maintaining high tensile strength.

Specification Summary & Compliance

This screw features a 4-40 UNC coarse thread with Class 2A tolerance for consistent fit and assembly ease. It is manufactured from 18-8 stainless steel with a passivated surface treatment, measuring 3/8" in length with a Rockwell B70 hardness. The product conforms to ASME B18.6.3 specifications for dimensional and mechanical requirements, and is verified as RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, ensuring adherence to environmental and safety standards.