Heli-coil A3591-4CNW500 Screw-locking Insert 1/4-28 Unf

Product Description

The HELI-COIL A3591-4CNW500 is a tangless screw-locking helical wire insert designed to create strong, vibration-resistant threads in drilled and tapped parent material. Manufactured from Grade 304 stainless steel with a dry film lubricant finish, this insert measures 0.5 inches in overall length at a 2D length-to-diameter ratio and accepts a 1/4-28 UNF screw thread. The locking feature provides a maximum locking torque of 30 inch-pounds while maintaining a minimum breakaway torque of 3.50 inch-pounds, making it well suited for joints that must resist loosening under load or vibration. Installation and removal do not require a tang break-off step, simplifying both the original assembly process and any future service work.

This insert is used in aerospace, industrial, and general mechanical applications where thread repair or thread reinforcement in softer parent materials is required. The stainless steel construction makes it appropriate for environments where corrosion resistance is a priority, including marine, chemical, and outdoor equipment service. It is installed by licensed mechanics, maintenance technicians, and precision assembly professionals using standard Heli-Coil compatible installation tooling.

Key Features

• Tangless design eliminates the tang break-off step during installation and removal
• Grade 304 stainless steel construction provides corrosion resistance in demanding environments
• Dry film lubricant finish reduces installation torque and protects the coil surface
• Maximum locking torque of 30 inch-pounds resists thread loosening under vibration
• Minimum breakaway torque of 3.50 inch-pounds ensures controlled, repeatable removal
• 2D length-to-diameter ratio with 0.5 inch overall length suits standard thread engagement depths

Compatibility

Designed as an OEM-style helical wire thread insert for tapped holes requiring 1/4-28 UNF internal threads in metallic or composite parent materials.

Installation Notes

Installation should be performed by qualified mechanical technicians using a Heli-Coil compatible tang-drive or tangless installation tool sized for 1/4-28 UNF inserts. The parent hole must be drilled and tapped to the correct Heli-Coil specification before insert installation. Verify that the installed insert sits flush with or slightly below the surface of the parent material before fastener engagement. Always follow the applicable engineering specification or manufacturer installation guide for torque and thread engagement requirements.