Heli-coil 8CBB Hand Sti Tap 1/2-13 Unc H3 Bottoming

Product Description

The HELI-COIL 8CBB is a hand STI (Screw Thread Insert) tap designed to cut the oversized internal threads required for installing helical wire thread inserts. Ground to an H3 thread limit with a 1/2-13 UNC profile, it produces a 3B class-of-fit thread that mates correctly with standard HELI-COIL insert stock. The bottoming chamfer geometry allows threading to the base of blind holes where a plug or taper tap cannot reach. Manufactured from high-speed steel with a bright uncoated finish, the 8CBB carries four flutes and an overall length of 3-13/16 inches with a thread length of 1-13/16 inches. Machinists, maintenance technicians, and field repair specialists use this tap to restore or create insert-ready threads in damaged or undersized bores.

The 8CBB is suited for thread repair and new-thread installations in metalworking, industrial maintenance, and MRO applications where helical inserts are specified. Its bottoming chamfer makes it particularly useful in blind-hole situations common in engine block repairs, fixture rework, and structural component maintenance. The tap is intended for hand operation and pairs with a standard tap wrench sized to its square drive.

Key Features

• 1/2-13 UNC thread profile with H3 thread limit for controlled insert-fit tolerance
• Bottoming chamfer enables threading to the full depth of blind holes
• Four flutes for efficient chip clearance during hand tapping
• High-speed steel construction provides wear resistance across a range of workpiece materials
• Bright uncoated finish - no coating buildup to affect thread tolerance
• 3B class of fit matched to standard HELI-COIL insert requirements

Compatibility

Designed for use in HELI-COIL thread repair and insert installation systems requiring a 1/2-13 UNC STI tap with H3 limit and bottoming chamfer geometry.

Installation Notes

This tap is intended for hand operation by a machinist or maintenance technician using an appropriately sized tap wrench. Before tapping, secure the workpiece and ensure the bore is drilled to the correct STI tap drill diameter per the insert manufacturer's specification. Apply cutting fluid appropriate for the workpiece material to extend tap life and improve thread finish. Never force the tap - back off periodically to break chips and prevent tap breakage, especially in blind holes.