Heli-coil 4FPB Hand Sti Tap 1/4-28 Unf H2 Plug Chamfer

Product Description

The HELI-COIL 4FPB is a hand STI (Screw Thread Insert) tap designed to cut the oversized threads required for installing Heli-Coil thread inserts into damaged or stripped bores. Ground from high-speed steel with a bright uncoated finish, this tap operates at a 1/4-28 UNF thread size with an H2 thread limit and a 3-flute, plug chamfer geometry. The plug chamfer provides a gradual lead-in suited for through-holes and most general tapping applications. Thread length measures 1.125 inches and overall length is approximately 2.72 inches, making it compact and manageable for close-quarters repair work on HVAC equipment, machinery, and mechanical assemblies.

This tap is intended for use by HVAC technicians, machinists, millwrights, and maintenance professionals performing thread repair on ferrous and non-ferrous materials. The STI profile cuts the specific thread form required before installation of 1/4-28 Heli-Coil inserts, restoring thread integrity in aluminum housings, cast iron components, and steel bodies. It is used as a hand tap - driven with a standard tap wrench - making it well suited for field repair scenarios where a machine tapping setup is not practical.

Key Features

• STI thread profile sized for 1/4-28 UNF Heli-Coil insert installation
• H2 thread limit for consistent fit with Class 3B tolerances
• 3-flute plug chamfer geometry for smooth entry in through-holes
• High-speed steel construction for durability across a range of workpiece materials
• Bright uncoated finish - no coating buildup that could affect dimensional accuracy
• Compact overall length of approximately 2.72 inches for use in confined spaces

Compatibility

Designed for use with 1/4-28 UNF Heli-Coil thread inserts requiring an STI-profile tap. This tap is not a standard thread tap and should only be used to prepare bores for Heli-Coil or equivalent screw thread insert installation.

Installation Notes

This tap is driven by hand using a standard tap wrench - it is not intended for machine tapping or power drivers. Secure the workpiece before tapping and apply cutting fluid appropriate to the workpiece material to extend tap life and improve thread quality. Back the tap out periodically to clear chips, especially in blind holes. Follow all applicable shop safety practices and consult thread repair insert manufacturer guidelines for correct drill size before tapping.