Heli-coil A3591-6CN750 Screw-locking Insert 3/8-24 Unf

Product Description

The HELI-COIL A3591-6CN750 is a tangless screw-locking helical wire insert designed to create a strong, vibration-resistant threaded connection in parent material. Manufactured from Grade 304 stainless steel with a bright finish, this insert accepts a 3/8-24 UNF fastener and measures 0.75 inches in overall length, corresponding to a 2D length-to-diameter ratio. The locking feature is achieved through a section of the coil that applies radial pressure on the mating fastener, resisting loosening under dynamic loads. Licensed electricians, millwrights, and maintenance technicians working in corrosive or high-vibration environments rely on this insert to restore or upgrade thread integrity in metal housings and assemblies.

This insert is suited for applications requiring a locked thread condition in stainless or similar substrates where vibration, thermal cycling, or repeated fastener removal could cause thread wear or loosening. Typical use cases include industrial equipment housings, marine hardware, aerospace ground support structures, and HVAC equipment frames. The tangless design eliminates the need to remove a drive tang after installation, reducing installation steps and eliminating the risk of tang fragments remaining in the assembly.

Key Features

• Tangless design eliminates post-installation tang removal and prevents debris in the assembly
• Grade 304 stainless steel construction resists corrosion in wet or chemically active environments
• Locking coil section delivers a maximum locking torque of 80 inch-pounds
• Minimum breakaway torque of 9.50 ounce-inches maintains thread engagement under vibration
• 15 free coils provide full helical engagement across the installed length
• Bright finish with outside diameter range of 0.448 to 0.468 inches for precise parent thread fit

Compatibility

Designed as an OEM-style screw-locking insert for tapped holes requiring a 3/8-24 UNF internal thread with a 2D insert length. Consult the HELI-COIL installation specification for the corresponding tap drill size and installation tool required for this insert series.

Installation Notes

Installation requires a HELI-COIL-specified 3/8-24 UNF STI tap to prepare the parent hole to the correct oversize diameter before the insert is driven in. Use the appropriate tangless installation tool for this insert series - do not attempt installation with a standard drive tool intended for tanged inserts. Ensure the parent material bore is clean, dry, and free of chips before driving the insert. Follow the manufacturers installation torque specification to seat the insert flush with or slightly below the parent surface.