Heli-coil 4CSB Spiral Point Sti Tap 1/4-20 Unc

Product Description

The HELI-COIL 4CSB is a spiral point STI tap designed for cutting internal threads in preparation for Heli-Coil thread insert installation. Built from high-speed steel with a bright, uncoated finish, this tap features a plug chamfer and two flutes for efficient chip evacuation during through-hole tapping operations. It is sized for 1/4-20 UNC threads, carries a Thread Limit of H2, and conforms to a 3B Class of Fit. The overall length is 2-23/32 inches with a thread length of 1-1/8 inches, making it suitable for standard-depth tapping in metal workpieces where thread inserts are required.

This tap is used when restoring stripped or damaged threads or when creating new STI (Screw Thread Insert) threads in materials such as aluminum, cast iron, or steel. The spiral point design pushes chips forward ahead of the tap, making it well-suited for blind or through-hole applications in production and repair environments. It is commonly used by machinists, maintenance technicians, and trade professionals performing thread repair on HVAC equipment housings, plumbing fixtures, and mechanical assemblies.

Key Features

• Spiral point geometry pushes chips forward, reducing clogging in through-hole tapping
• High-speed steel construction provides durability across ferrous and non-ferrous materials
• Plug chamfer allows gradual thread engagement for controlled cutting
• H2 thread limit and 3B class of fit ensure proper STI thread form for insert installation
• Bright, uncoated finish for general-purpose use without added friction from coatings
• Two-flute design balances chip clearance and cutting strength at 1/4-20 UNC size

Compatibility

Designed as an OEM-style STI tap for use with Heli-Coil thread insert systems in 1/4-20 UNC thread repair and new thread formation applications.

Installation Notes

Installation is typically performed by machinists or maintenance technicians using a tap wrench or machine tapping setup. Always ensure the workpiece is securely clamped and the tap is properly aligned before beginning. Power down and de-energize any equipment before performing thread repair on assembled machinery. Use appropriate cutting fluid for the base material to extend tap life and improve thread quality.