Heli-coil A1191-4CNPF500 Free Running Insert 1/4-28 Unf

Product Description

The HELI-COIL A1191-4CNPF500 is a free running helical wire thread insert designed to create or restore strong, durable internal threads in a tapped host material. Manufactured from 304 stainless steel with a primer-free finish, this insert measures 0.5 inches overall length and accepts a 1/4-28 UNF thread. The tanged design allows for installation using a standard installation tool, with the tang providing the driving surface during insertion. This insert carries an 11-3/8 free coil count and a 2D length-to-diameter ratio, making it suitable for applications that require reliable thread strength in a compact footprint. Machinists, maintenance technicians, and field service professionals commonly install these in metalworking and repair operations.

Free running inserts of this type are used across industrial, mechanical, and maintenance applications where thread repair or thread reinforcement is needed. The 1/4-28 UNF thread size is common in precision assemblies, automotive, aerospace ground support, and general manufacturing environments. The primer-free finish is suited for installations where no coating adhesion preparation is required. This insert is sold individually and is typically installed in quantities consistent with the application requirement.

Key Features

• 1/4-28 UNF thread size for precision fine-thread applications
• 304 stainless steel construction for corrosion resistance and strength
• 0.5 inches overall length with a 2D length-to-diameter ratio
• Tanged design for positive engagement during installation with a standard insert tool
• Primer-free finish requires no additional surface preparation before installation
• 11-3/8 free coil count for consistent thread engagement across full insert length

Compatibility

Designed as an OEM-style replacement or new-installation insert for any application requiring a 1/4-28 UNF free running threaded insert in a properly prepared tapped bore.

Installation Notes

Installation is performed using a compatible helical insert installation tool sized for 1/4-28 UNF thread. The tang is used to drive the insert into the tapped hole and should be broken off after installation using a tang break-off tool where the application requires a tang-free bore. Ensure the host material is tapped to the correct STI (Screw Thread Insert) tap size before installation. Always de-energize or isolate any equipment before performing thread repair work on assembled components.