Heli-coil A3585-4CN375 Screw-locking Insert 1/4-20 Unc

Product Description

The HELI-COIL A3585-4CN375 is a tangless screw-locking helical coil insert designed to create or restore durable, vibration-resistant threaded holes in a wide range of base materials. Built from Grade 304 stainless steel with a bright finish, it accepts a 1/4-20 UNC screw thread and measures 0.375 inches in overall length, corresponding to a 1-1/2D length-to-diameter ratio. The locking feature is achieved through a deformed coil section that applies controlled radial pressure against the mating fastener, with a maximum locking torque of 30 in/lb and a minimum breakaway torque of 4.50 in/lb. The tangless design eliminates the need to remove a tang after installation, reducing assembly steps and debris risk in blind-hole applications. Machinists, maintenance technicians, and assembly professionals install these inserts.

This insert is suited for applications where thread strength, corrosion resistance, and vibration resistance are required in aluminum, magnesium, cast iron, plastics, and other materials with lower base-thread strength than the fastener. The 1/4-20 UNC thread form is common across general industrial, aerospace, and mechanical assembly work. The 5-3/4 free coil count and 0.375-inch length make it appropriate for standard fastener engagement depths in thinner or space-constrained workpieces. It is sold individually, with a minimum order quantity of 10 units.

Key Features

• Tangless design eliminates post-installation tang removal, reducing assembly time and contamination risk in blind holes
• Grade 304 stainless steel construction provides corrosion resistance and long service life
• 1/4-20 UNC thread form with 0.375 inches overall length at a 1-1/2D length-to-diameter ratio
• Maximum locking torque of 30 in/lb with a minimum breakaway torque of 4.50 in/lb for reliable vibration resistance
• Outside diameter range of 0.310 to 0.330 inches for consistent fit in standard Heli-Coil tapped holes
• Bright finish with 5-3/4 free coils for uniform thread engagement

Compatibility

Designed as an OEM-style replacement or new-installation insert for standard 1/4-20 UNC Heli-Coil tapped holes in base materials requiring thread repair or thread reinforcement.

Installation Notes

Installation requires a properly sized Heli-Coil tap to prepare the receiving hole to the correct diameter and thread form before the insert is driven in. A Heli-Coil installation tool compatible with the tangless insert style should be used to drive the coil to the correct depth without damaging the coil geometry. Power down or de-energize any assembly before thread repair work begins on live components. Follow the tool manufacturer torque guidelines and inspect the installed insert for full seating before assembling the mating fastener.