Heli-coil 8187-10 Hand Sti Tap 5/8-11 Unc H3 Plug Chamfer

Product Description

The HELI-COIL 8187-10 is a hand STI (Screw Thread Insert) tap designed to cut oversized threads in a parent material so that a helical wire insert can be installed to restore or create a new threaded bore. Manufactured from high-speed steel with a bright, uncoated finish, this tap cuts a 5/8-11 UNC thread profile to an H3 thread limit, providing consistent sizing for Class 3B fit applications. The 4-flute, plug chamfer geometry eases starting alignment and distributes cutting load evenly across the flute set. Overall length is 4.25 inches with a 2-inch thread length, making it suited for through-hole and moderate-depth blind-hole operations.

This tap is used in MRO, manufacturing, and field repair applications where stripped or damaged 5/8-11 UNC threaded holes need to be rebuilt using helical wire inserts. Typical scenarios include heavy equipment repair, engine block thread restoration, and structural fastener hole rehabilitation in metal components. Installation is performed by hand or with a standard tap wrench. The plug chamfer makes it appropriate for through holes or blind holes with adequate clearance depth. Machinists, millwrights, and field service technicians working in industrial and mechanical trade environments are the primary installers.

Key Features

• 5/8-11 UNC thread profile with H3 thread limit for Class 3B fit precision
• High-speed steel construction for durability across ferrous and non-ferrous base materials
• 4-flute design distributes cutting forces evenly and supports chip clearance
• Plug chamfer geometry aids tap alignment at entry and suits through-hole and open blind-hole applications
• Bright, uncoated finish - no coating buildup to affect final thread dimensions
• 0.59-inch shank diameter and 4.25-inch overall length fit standard tap wrenches and holders

Compatibility

Designed as an OEM-style STI tap for use with helical wire insert systems requiring a 5/8-11 UNC oversized threaded bore prepared to Class 3B fit tolerances.

Installation Notes

This tap is operated by hand using a tap wrench - do not run it in a power driver without appropriate torque control, as HSS taps can snap under sudden torsional overload. Secure the workpiece firmly before tapping and apply a suitable cutting fluid to extend tap life and improve thread finish in steel and aluminum. Back the tap off periodically to break chips and prevent clogging, particularly in blind holes. Follow the thread insert manufacturer's specifications for tap drill size before using this STI tap.