S-90390A551 1/4"-20 x 2 1/4" Tapping Screws

Key Features & Benefits at a Glance

• Superior torque transfer with T30 Torx drive, reducing cam-out and tool wear during installation
• Enhanced corrosion resistance from black-phosphate steel coating, ideal for demanding industrial environments
• Self-tapping efficiency with Type F thread cutting design for fast, secure installation in aluminum, brass, cast iron, and sheet metal
• Precise flush mounting enabled by 82° countersink angle and standard flat head profile
• Full-thread engagement along the 2 1/4" length for maximum holding power in various material thicknesses
• Optimized drilling compatibility with No. 1 drill bit (0.228" diameter) for accurate pilot hole preparation
• Reliable coarse threading (UNC 1/4-20) providing strong grip and resistance to vibration loosening

Professional Applications & Engineering Value

These 1/4-20 UNC tapping screws deliver exceptional performance in metal fabrication and assembly operations. The black-phosphate steel construction provides a durable barrier against oxidation, while the Type F thread cutting design eliminates the need for pre-tapped holes, significantly reducing installation time in aluminum, brass, cast iron, and sheet metal applications. The T30 Torx drive ensures maximum torque transmission without slippage, preventing damage to fastener heads and extending tool life. With fully threaded coverage and 82° countersink geometry, these screws create secure, flush-mount connections that maintain integrity under vibration and load stresses common in industrial equipment, automotive components, and structural frameworks.

Specification Summary & Compliance

Manufactured to UNC 1/4-20 thread standards with coarse spacing for rapid installation. Features Class 2A thread tolerances ensuring consistent fit and performance. The flat head profile conforms to industry standards with 82° countersink angle for proper seating. Compatible with No. 1 drill bit (0.228" diameter) for pilot hole preparation. Constructed from steel with black phosphate coating for corrosion protection. Right-hand thread cutting (Type F) design optimized for metal applications. Complies with RoHS and REACH environmental standards for industrial use.