Heli-coil A3585-4EN500 Screw-locking Insert 1/4-20 Unc

Product Description

The HELI-COIL A3585-4EN500 is a screw-locking helical coil insert designed to create a secure, vibration-resistant threaded hole in a parent material. It accepts a 1/4-20 UNC fastener and installs into a prepared tapped hole to restore or reinforce thread integrity. The insert is manufactured from grade 18-8 stainless steel with an uncoated finish, making it suitable for corrosive or high-humidity environments. At 0.5 inches in overall length with a 2D length-to-diameter ratio, it delivers a compact footprint without sacrificing locking performance. Machinists, maintenance technicians, and field service professionals across HVAC, plumbing, and industrial trades rely on inserts like this to repair stripped threads or build out thread strength in soft-metal housings.

This insert is appropriate for both new installation and thread repair applications in light-gauge aluminum, cast housings, and similar parent materials where thread stripping is a common failure mode. It is well-suited for use in residential and commercial HVAC equipment, pump housings, motor mounts, and other assemblies that experience recurring vibration or thermal cycling. The screw-locking feature - provided by one or more deformed coils that grip the mating fastener - resists loosening under dynamic load without requiring adhesive thread-locking compounds.

Key Features

• 1/4-20 UNC thread size for broad fastener compatibility
• 2D insert length (0.5 inches OAL) for compact installations in thin or shallow bosses
• Grade 18-8 stainless steel construction resists corrosion and oxidation
• Tanged design for standard installation tooling; tang breaks off after installation
• Maximum locking torque of 30 inch-pounds with a minimum breakaway torque of 4.50 inch-pounds
• 8 free coils provide consistent engagement across the full insert length
• Uncoated finish - no coating interference with dimensional tolerances

Compatibility

Designed as an OEM-style and repair-grade threaded insert for any parent material tapped to accept a 1/4-20 UNC helical coil insert with a minimum outside diameter of 0.31 inches and a maximum outside diameter of 0.33 inches.

Installation Notes

Installation requires a properly sized STI (Screw Thread Insert) tap and the appropriate HELI-COIL installation tool for 1/4-20 UNC inserts. Power down and de-energize any equipment before drilling or tapping in the field. After driving the insert to the correct depth, break off the installation tang using the tang break-off tool or needle-nose pliers - never leave the tang in the hole, as it can cause fastener interference or damage. Follow the insert manufacturer's installation guide for correct pre-hole depth and tap drill size to maintain thread class tolerances.