Heli-coil A1185-4CNPF375 Free Running Insert 1/4-20 Unc

Product Description

The HELI-COIL A1185-4CNPF375 is a free running wire thread insert designed to create or restore durable internal threads in tapped holes. The insert accepts a 1/4-20 UNC thread and measures 0.375 inches overall in length, which corresponds to a 1.5D length-to-diameter ratio. Constructed from 304 stainless steel with a primer-free finish, it resists corrosion and requires no additional surface prep before installation. The tanged style allows for standard installation tooling. Machinists, maintenance technicians, and field service professionals use these inserts in metal repair and new-part fabrication where stripped or weak parent-material threads need reinforcement.

This insert is suited for general industrial and MRO applications where 1/4-20 UNC thread repair or reinforcement is required. Typical scenarios include restoring threads in aluminum, cast iron, magnesium, or steel housings across HVAC equipment, electrical enclosures, pumps, and other mechanical assemblies. The 0.375 inch installed length provides a reliable thread engagement depth in moderate-load applications. The primer-free finish allows direct installation without surface pre-treatment.

Key Features

• 1/4-20 UNC thread size fits common fastener stock in trade and industrial applications
• 0.375 inch overall length with 1.5D length-to-diameter ratio for consistent engagement
• 304 stainless steel construction resists corrosion in harsh or outdoor environments
• Tanged design compatible with standard HELI-COIL installation tools
• Primer-free finish allows immediate installation without surface preparation
• 5-3/4 free coils provide full thread coverage across the insert length

Compatibility

Designed as an OEM-style free running insert for use in any tapped hole requiring 1/4-20 UNC internal threads. Suitable for new-build and repair applications in parent materials including aluminum, steel, cast iron, and magnesium.

Installation Notes

Installation should be performed by a qualified machinist or maintenance technician using the appropriate HELI-COIL installation driver for the 1/4-20 insert size. Ensure the tapped hole meets the required oversize drill and tap specifications for free running wire inserts before driving. After installation, break off the drive tang using a tang break-off tool or a sharp punch; verify the tang is fully removed from the hole before assembling fasteners. Shut down and de-energize any equipment before performing thread repair on live assemblies.