Heli-coil A3585-4CNW375 Screw-locking Insert 1/4-20 Unc

Product Description

The HELI-COIL A3585-4CNW375 is a tangless screw-locking helical coil insert designed to create a durable, vibration-resistant threaded connection in parent material tapped to 1/4-20 UNC. Manufactured from Grade 304 stainless steel with a dry film lubricant finish, this insert resists corrosion and galling during installation and service. At 0.375 inches overall length, it provides a 1-1/2D engagement depth suited to thin or medium-section assemblies. The locking feature uses a section of distorted coils to apply radial pressure on the fastener thread, preventing loosening under vibration or dynamic load. Licensed machinists, maintenance technicians, and assembly professionals install this type of insert.

This insert is used in applications where a reliable locking thread is required in aluminum, magnesium, cast iron, plastics, or other materials that cannot sustain direct thread engagement under repeated cycling or high vibration. Typical install scenarios include aerospace assemblies, industrial equipment frames, HVAC component housings, and fluid system manifolds where 1/4-20 UNC fasteners must remain secured without chemical thread-locking compounds. The tangless design eliminates the need for tang removal after installation, reducing debris risk in critical assemblies and simplifying the installation workflow in blind-hole applications.

Key Features

• Grade 304 stainless steel construction resists corrosion and galling in harsh or wet environments
• Tangless design eliminates post-installation tang breakoff, reducing debris contamination risk
• Dry film lubricant finish promotes consistent installation torque and reduces thread damage during driving
• Maximum locking torque of 30 inch-pounds with a minimum breakaway torque of 4.50 inch-pounds for reliable vibration resistance
• 5-3/4 free coils provide consistent thread engagement across the full 0.375-inch insert length
• Outside diameter range of 0.310 to 0.330 inches ensures positive interference fit in a properly tapped hole

Compatibility

Designed as an OEM-style replacement or new-installation insert for 1/4-20 UNC tapped holes requiring a 1-1/2D locking thread insert in stainless steel.

Installation Notes

Installation requires a correctly sized HELI-COIL or compatible tangless insert installation tool; do not attempt to drive the insert with a standard screwdriver or improvised tool. The parent hole must be tapped with the appropriate STI (Screw Thread Insert) tap to achieve the correct minor diameter for proper coil interference. Verify hole depth and cleanliness before installation to prevent cross-threading or incomplete seating. Technicians should follow applicable torque specifications from the assembly drawing or OEM documentation, as insert performance depends on proper hole preparation and installation technique.