Import BDNA-22591 Hand Sti Tap 1/4-28 Unf H2 Plug Chamfer

Product Description

The IMPORT BDNA-22591 is a hand STI (Screw Thread Insert) tap ground to 1/4-28 UNF specifications with an H2 thread limit and a 3-flute plug chamfer geometry. It is designed to cut threads into pre-drilled holes in preparation for helical coil thread inserts, restoring or creating strong, wear-resistant threaded connections in metal components. The plug chamfer allows starting in a through-hole or blind hole with adequate depth. Made from high-speed steel with a bright uncoated finish, this tap is suited for hand tapping operations across HVAC, plumbing, electrical, and mechanical service applications where thread repair or insert installation is required.

This tap is used in trade service settings where damaged or stripped threads in aluminum, cast iron, or mild steel components need to be restored using helical coil inserts. It is appropriate for residential and light commercial equipment maintenance and repair work, including field service on HVAC equipment housings, pump bodies, electrical enclosures, and similar threaded assemblies. The Helicoil reference number for this tap is 4FPB, which corresponds to its STI thread geometry.

Key Features

• 1/4-28 UNF thread form with H2 thread limit for controlled fit tolerance
• 3-flute plug chamfer design for starting in through-holes or sufficiently deep blind holes
• STI geometry prepares holes to accept helical coil thread inserts
• High-speed steel construction for durability in ferrous and non-ferrous metals
• Bright uncoated finish suitable for general-purpose hand tapping
• Thread length of 1.125 inches and overall length of approximately 2.719 inches

Compatibility

Designed for use with 1/4-28 UNF helical coil thread insert systems; Helicoil reference number 4FPB. Intended for hand tapping operations only and is not rated for machine or power tapping use.

Installation Notes

This tap is intended for hand use only — apply steady, even torque with an appropriate tap wrench and back off periodically to break chips. Power down and de-energize any equipment before performing thread repair work on or near electrical or mechanical assemblies. Follow applicable safety procedures for the equipment type being serviced. Ensure the pilot hole is drilled to the correct STI tap drill size for 1/4-28 UNF inserts before tapping.