Heli-coil 04FSB Spiral Point Sti Tap 4-48 Unf Plug Hss

Product Description

The HELI-COIL 04FSB is a spiral point STI tap designed to cut threads for Heli-Coil wire thread inserts in 4-48 UNF applications. Made from high-speed steel with a bright, uncoated finish, it features 2 flutes and a plug chamfer that drives chips forward during through-hole tapping operations. The overall length is 2 inches with a thread length of 11/16 inches. The H1 thread limit and 3B class of fit ensure the oversized thread geometry required for proper insert seating. This tap is used by machinists, maintenance technicians, and field repair professionals who need to restore or install Heli-Coil inserts in threaded bores.

The 04FSB is suited for use in thread repair and insert installation work across industrial, HVAC equipment, and mechanical maintenance applications. It produces the enlarged STI (Screw Thread Insert) tapped hole that accepts a Heli-Coil insert, which in turn restores the bore to standard 4-48 UNF thread dimensions. The plug chamfer makes it appropriate for through-hole and sufficiently deep blind-hole operations where chip clearance is available. It is typically used with a tap wrench or machine tap holder at low speeds.

Key Features

• STI thread form produces oversized bore sized for Heli-Coil wire thread insert installation
• High-speed steel construction provides durability across a range of base materials
• Plug chamfer advances chips forward, suited for through-hole and deep blind-hole tapping
• H1 thread limit with 3B class of fit for consistent insert fit and function
• 2-flute design for efficient chip evacuation in typical repair and production tapping
• Bright, uncoated finish - no coating buildup concerns in close-tolerance STI applications

Compatibility

Designed for use in Heli-Coil insert installation systems requiring a 4-48 UNF STI tapped hole. Compatible with standard Heli-Coil wire thread insert kits and tooling for the 4-48 thread size.

Installation Notes

Installation should be performed by a qualified machinist or maintenance technician familiar with thread insert systems. Power down and de-energize any equipment before performing thread repair work on installed assemblies. Use a calibrated tap wrench or low-speed machine holder to avoid tap breakage in small-diameter applications. Follow the Heli-Coil system procedure for drill size, tapping, and insert installation sequence to ensure proper thread form and insert retention.