Heli-coil 7551-5 Thread Insert Tool 5/16-18 Unc

Product Description

The HELI-COIL 7551-5 is a hand installation tool designed to install wire thread inserts into prepared holes. It uses a Type II Prewinder mechanism to compress the insert for controlled, accurate placement without power tools. The prewinder body measures 0.625 inches in diameter and 4.625 inches in length, with a spinner diameter of 3.719 inches for comfortable hand operation. This tool is sized for 5/16-18 UNC threads and works with both free-running and locking insert types. It is used by machinists, maintenance technicians, and field service professionals performing thread repair or thread reinforcement work on metal assemblies.

This tool is suited for repair shops, production floors, and field maintenance environments where stripped or damaged 5/16-18 UNC threaded holes need to be restored to full thread strength. The Type II Prewinder design allows the installer to load the insert onto the mandrel and drive it into the prepared hole in a single controlled motion. It is appropriate for both free-running inserts, which provide clean thread engagement, and locking inserts, which add prevailing torque resistance to the fastened joint.

Key Features

• Sized for 5/16-18 UNC thread inserts
• Compatible with both free-running and locking wire thread inserts
• Type II Prewinder mechanism compresses insert for clean, accurate installation
• Prewinder body diameter of 0.625 inches fits standard insert installation workflow
• Spinner diameter of 3.719 inches provides controlled hand torque
• Hand-operated design requires no power source for field or bench use

Compatibility

Designed for use with 5/16-18 UNC free-running and locking wire thread inserts in standard hand installation applications.

Installation Notes

Installation is performed by hand and does not require electrical power or compressed air. The threaded hole must be properly drilled and tapped to the correct insert tap size before using this tool. Ensure the insert is correctly seated on the prewinder mandrel before driving to avoid cross-threading or insert damage. Follow the insert manufacturer's depth and engagement specifications for the base material being repaired.