Hertel K007051AS Hand Sti Tap 1/4-20 Unc H3 Plug Chamfer

Product Description

The HERTEL K007051AS is a hand STI tap designed for cutting Screw Thread Insert (STI) threads in a 1/4-20 UNC pattern. STI taps cut an oversized thread profile to accept helical wire inserts, restoring or reinforcing threaded holes in softer base materials. This tap carries an H3 thread limit for consistent fit with standard STI insert systems. It features a plug chamfer with 3 flutes, providing a balance of cutting action and chip clearance suitable for through-holes and moderately deep blind holes. Machined from high-speed steel with a bright, uncoated finish, it is suited for hand tapping operations in machine shops, maintenance, and field repair environments.

This tap is used when installing helical wire thread inserts to repair stripped or damaged threads, or to create stronger thread forms in aluminum, magnesium, cast iron, and similar materials. The plug chamfer makes it appropriate for through-holes or blind holes with adequate depth. It is typically used by machinists, maintenance technicians, and field service professionals working on equipment repair, aerospace components, or general industrial assemblies where thread reinforcement is required.

Key Features

• STI thread form cuts oversized profile for helical wire insert installation
• 1/4-20 UNC thread size with H3 thread limit for precise fit
• Plug chamfer with 3-5 thread lead for versatile through-hole and blind-hole use
• 3-flute design balances chip evacuation and cutting efficiency
• High-speed steel construction provides durability across a range of workpiece materials
• Bright uncoated finish suitable for use with standard cutting fluids
• Helicoil reference number 4CPA for cross-referencing with insert system tooling

Compatibility

Compatible with standard Helicoil-style STI insert systems referencing part number 4CPA. Designed as an OEM-style replacement or equivalent hand tap for 1/4-20 UNC STI thread insert applications.

Installation Notes

This tap is intended for hand tapping operations and should be used with a properly sized tap wrench. Apply cutting fluid appropriate for the workpiece material before and during tapping to reduce heat and extend tool life. Ensure the tap is started square to the workpiece surface to avoid thread misalignment or tap breakage. Follow applicable shop safety practices and wear appropriate eye protection when performing tapping operations.