Osg 1714401 Spiral Flute Sti Tap 1/4-28 Unf 3 Flute

Product Description

The OSG 1714401 is a spiral flute STI (Screw Thread Insert) tap designed for cutting oversized internal threads that accept helical wire inserts such as Heli-Coil-style thread repair inserts. Built from vanadium high-speed steel with a steam oxide finish, this tap delivers consistent performance in demanding threading applications. It features a 45-degree helix angle that promotes efficient chip evacuation in blind and through holes. The modified bottoming chamfer allows threading close to the bottom of a hole while maintaining controlled entry. Thread specification is 1/4-28 UNF with an H3 thread limit and 3 right-hand flutes.

This tap is suited for machining and maintenance professionals working with carbon steel, hardened steel, and stainless steel. Typical applications include thread repair and insert preparation in manufacturing, aerospace, automotive, and general metalworking environments. The STI geometry produces the correct oversized thread profile required before installing a helical wire thread insert to restore a damaged or stripped hole to original thread size and strength. Overall length is 2.5 inches with a shank diameter of 0.255 inches and a thread length of 1 inch, making it compatible with standard tap holders and machine spindles used in both manual and CNC operations.

Key Features

• STI thread profile produces the correct oversize thread for helical wire insert installation
• 45-degree helix angle promotes upward chip evacuation, reducing clogging in blind holes
• Modified bottoming chamfer allows threading close to the bottom of a blind hole
• Vanadium high-speed steel construction provides wear resistance and toughness in ferrous materials
• Steam oxide finish improves lubricity and reduces friction during cutting
• H3 thread limit ensures consistent fit with standard helical insert tolerances

Compatibility

Designed for use in carbon steel, hardened steel, and stainless steel workpieces. Produces a 1/4-28 UNF STI thread for use with standard helical wire thread inserts of the corresponding size.

Installation Notes

Installation is performed by machinists or maintenance technicians using a standard tap wrench, tapping head, or CNC spindle with appropriate tap holder. Always apply cutting fluid suited to the workpiece material before and during tapping to reduce heat and extend tool life. Secure the workpiece firmly and ensure the tap is properly aligned with the pilot hole before applying torque. Follow the insert manufacturer's specifications for pilot hole diameter when drilling before using this STI tap.