Emuge BU513710.5639 Spiral Point Sti Tap 1/4-28 Unf

Product Description

The EMUGE BU513710.5639 is a spiral point STI tap designed for threading 1/4-28 UNF inserts into blind holes. Built from cobalt high-speed steel with a Titanium Nitride (TiN) coating, it delivers extended tool life in demanding materials including stainless steel and carbon steel. The tap features a bottoming chamfer for threading close to the bottom of a blind hole, 3 flutes, an H2 thread limit, and a 3B class of fit. Overall length is 3.543 inches with a thread length of 0.3571 inches. It is intended for use by machinists, maintenance technicians, and trade professionals performing precision threaded insert installations.

This tap is used in applications where a STI (Screw Thread Insert) is required to restore or create a standard 1/4-28 UNF thread in a blind hole. Typical install scenarios include repair work on stripped threads in steel or stainless steel components, as well as new production threading operations where insert-style thread reinforcement is specified. The bottoming chamfer style allows full thread engagement depth even in shallow blind holes, making it well suited for tight-tolerance mechanical assemblies in industrial, aerospace-adjacent maintenance, and heavy equipment service environments.

Key Features

• STI thread form for use with 1/4-28 UNF threaded inserts in blind holes
• Cobalt HSS construction provides heat and wear resistance in stainless steel and alloy steel
• Titanium Nitride (TiN) coating reduces friction and extends cutting edge life
• Bottoming chamfer allows threading to near the base of a blind hole
• H2 thread limit and 3B class of fit ensure consistent, controlled thread tolerances
• 3 flutes with spiral point geometry push chips forward during through and blind hole operations

Compatibility

Designed for cutting 1/4-28 UNF STI threads in stainless steel and steel workpieces. Intended for use with 1/4-28 UNF threaded insert installation in blind hole applications per Series BU513710 specifications.

Installation Notes

This tap should be installed and operated by qualified machinists or skilled maintenance technicians familiar with tapping speeds, cutting fluids, and thread insert procedures. Always secure the workpiece and use appropriate cutting fluid for the material being tapped, particularly when working with stainless steel. Ensure the tap is aligned perpendicular to the workpiece surface before beginning the cut to avoid thread damage or tap breakage. Follow machine shop safety practices and consult applicable tooling manufacturer guidance for recommended RPM and feed rates.