Heli-coil A3759-4CN500 Threaded Insert 1/4-28 Unf 2D

Product Description

The HELI-COIL A3759-4CN500 is a tangless screw-locking helical wire insert designed to create durable, wear-resistant internal threads in parent materials that require reliable thread reinforcement. Manufactured from stainless steel with a bright finish, this insert measures 0.5 inches in overall length and conforms to a 2D length-to-diameter ratio for the 1/4-28 UNF thread standard. The screw-locking design uses a specific number of coils deformed slightly out of round to apply radial pressure on the mating fastener, resisting loosening from vibration or dynamic loads. Installation is performed by machinists, maintenance technicians, and MRO professionals using a standard Heli-Coil installation tool and the appropriate drill and tap.

This insert is suited for applications where thread stripping in soft base materials is a concern, or where worn threads in metal housings, castings, or structural components need restoration to original specification. The 1/4-28 UNF fine-thread profile is common in aerospace, industrial equipment, and precision mechanical assemblies. The stainless steel construction makes this insert appropriate for environments with exposure to moisture, mild corrosives, or elevated temperatures where carbon steel inserts would be less suitable.

Key Features

• Tangless design eliminates tang removal after installation, reducing the risk of loose fragments in the assembly
• Screw-locking function provides maximum locking torque of 90 in/lb and minimum breakaway torque of 52 in/lb
• 1/4-28 UNF thread standard with 0.5 inch overall length at 2D length-to-diameter ratio
• 8 free coils deliver consistent locking engagement across the insert length
• Stainless steel construction with bright finish for corrosion resistance in demanding service environments

Compatibility

Designed as an OEM-style threaded insert for 1/4-28 UNF tapped holes prepared to standard Heli-Coil installation specifications in metallic or composite parent materials.

Installation Notes

Installation requires a properly sized Heli-Coil drill, tap, and insertion tool specific to the 1/4-28 UNF tangless insert series. The parent material must be drilled and tapped to the correct Heli-Coil oversize dimensions before insert installation. Ensure all chips and debris are cleared from the tapped hole before driving the insert to full depth. Follow applicable torque and inspection requirements per the governing assembly specification or engineering drawing.