Heli-coil A3591-5CN312 Screw-locking Insert 5/16-24 Unf

Product Description

The HELI-COIL A3591-5CN312 is a tangless screw-locking helical wire insert designed to create strong, vibration-resistant threads in tapped holes. It accepts a 5/16-24 UNF mating thread and measures 0.312 inches in overall length, placing it in the 1D length-to-diameter class. Manufactured from Grade 304 stainless steel with a bright finish, it delivers corrosion resistance suitable for demanding service environments. The screw-locking design provides a maximum locking torque of 60 in/lb, keeping fasteners secure against vibration and shock loading. Licensed technicians and maintenance professionals in HVAC, industrial, and equipment repair applications install these inserts to restore or reinforce threaded holes.

This insert is suited for use in metallic and high-strength plastic parent materials where a durable internal thread repair or thread reinforcement is needed. The 5/16-24 UNF thread size is common in precision equipment, automotive, aerospace ground support, and mechanical assemblies. The tangless design eliminates the need for a tang break-off step after installation, simplifying the install process and reducing the risk of loose tang fragments inside assemblies. It is appropriate for residential and commercial maintenance scenarios wherever a stripped or damaged UNF thread must be restored to full rated strength.

Key Features

• 5/16-24 UNF thread size with 1D length-to-diameter ratio for standard-depth installations
• Tangless design removes the tang break-off step and eliminates loose fragment risk
• Grade 304 stainless steel construction provides corrosion and heat resistance
• Maximum locking torque of 60 in/lb holds fasteners against vibration and shock
• Minimum break-away torque of 6.50 oz-in ensures reliable locking engagement
• Bright finish with outside diameter range of 0.380 to 0.400 inches for consistent fit

Compatibility

Designed as an OEM-style screw-locking insert for applications requiring a 5/16-24 UNF internal thread repair or reinforcement in parent materials compatible with helical wire insert installation.

Installation Notes

Installation is performed by machinists, maintenance technicians, and trade professionals using the appropriate HELI-COIL tap and tangless insert tool for the 5/16-24 UNF thread series. The parent material hole must be drilled and tapped to the correct insert tap size before installation. Power down or de-energize any equipment and relieve all pressure or load before performing thread repair in service. Follow the insert manufacturer installation procedures to achieve proper seating depth and avoid over-driving the insert.