S-91381A359 1/4"-28 x 1" ASME B18.3 Set Screws

Key Features & Benefits at a Glance

• Superior Thread Precision – Class 3A thread fit ensures tighter tolerances and reliable, vibration-resistant fastening in demanding applications.
• Enhanced Durability & Corrosion Resistance – Black-Oxide Alloy Steel with Rockwell C28 hardness provides long-lasting strength and moderate corrosion protection.
• Surface-Safe Fastening – Integrated brass soft tip prevents damage to mating surfaces while maintaining a secure, non-marring hold.
• Easy Installation in Confined Spaces – Headless design with 1/8" hex drive allows for simple tool access and adjustment in tight assemblies.
• Consistent Performance Under Stress – Fine thread spacing (UNF) offers improved load distribution and resistance to loosening under dynamic conditions.
• Broad Industry Compliance – Meets ASME B18.3 specifications and is RoHS 3 & REACH compliant, ensuring suitability for regulated and international markets.
• Reliable Right-Hand Threading – Standard thread direction facilitates straightforward installation and removal with common tools.

Professional Applications & Engineering Value

This 1/4"-28 UNF Class 3A set screw is engineered to address common industrial challenges such as component slippage, surface damage, and fastener failure under vibration. The Black-Oxide Alloy Steel construction, combined with a Rockwell C28 hardness, ensures the screw withstands repetitive stress and moderate environmental exposure. The brass soft tip is critical for applications requiring frequent adjustments—like precision machinery, motor shafts, and coupling assemblies—where it protects costly components from scratching or indentation. Its headless hex drive design is ideal for compact spaces, allowing secure fastening without protruding hardware. By integrating fine UNF threads and a Class 3A fit, this set screw delivers enhanced clamping force and resistance to loosening, making it a dependable choice for OEMs and maintenance teams in automotive, aerospace, and industrial equipment sectors.

Specification Summary & Compliance

This set screw adheres to ASME B18.3 standards, with a Class 3A thread fit for precise, high-tolerance assemblies. It features a 1/4"-28 UNF fine thread with right-hand direction and is manufactured from Black-Oxide Alloy Steel for consistent performance. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring it meets environmental and safety requirements for global supply chains.