Osg 0144808 Spiral Flute Sti Tap 4-40 Unc Hss

Product Description

The OSG 0144808 is a high-speed steel spiral flute STI tap designed for cutting Screw Thread Insert (STI) threads in a 4-40 UNC configuration. With a 45-degree right-hand helix and a bottoming chamfer, this tap drives chips up and out of the hole, making it well-suited for blind-hole tapping operations where chip evacuation is critical. The V finish coating provides surface hardness and lubricity to extend tool life under production conditions. At 2 inches overall length with a 0.141-inch shank diameter, this is a compact threading tool sized for small-fastener work in metal components.

This tap is used in machining and metalworking applications where STI threaded inserts are required to repair or reinforce tapped holes. The 4-40 UNC thread standard and 2B class of fit make it appropriate for precision assemblies in aerospace, electronics, and general manufacturing. The bottoming chamfer allows threads to be cut close to the bottom of a blind hole, maximizing usable thread engagement. Licensed machinists, tool-and-die makers, and maintenance technicians working with fine-thread fastener systems will find this tap useful for both production and repair tapping jobs.

Key Features

• 4-40 UNC thread form with STI profile for screw thread insert applications
• 45-degree right-hand spiral flute helix promotes upward chip evacuation in blind holes
• Bottoming chamfer enables threading close to the bottom of blind holes
• High-speed steel construction provides toughness for a wide range of workpiece materials
• V finish coating adds surface lubricity and wear resistance
• H2 thread limit and 2B class of fit for consistent, controlled thread tolerance

Compatibility

Designed for use in standard 4-40 UNC STI tapping applications requiring a bottoming chamfer and spiral flute geometry; compatible with standard tapping chucks and holders accepting a 0.141-inch round shank.

Installation Notes

This tap should be installed by a qualified machinist or maintenance technician using appropriate tapping equipment. Ensure the workpiece is securely fixtured and the tap is properly aligned with the pre-drilled STI pilot hole before engaging the cut. Apply cutting fluid suitable for the workpiece material to reduce heat buildup and extend tap life. Inspect the tap for wear or chipping before each use and replace if damage is observed.