Balax 18666-010 Thread Forming Sti Tap M8 X 1.25 Bottoming

Product Description

The BALAX 18666-010 is a thread forming STI (Screw Thread Insert) tap designed to produce internal threads for helical insert applications without generating chips. Manufactured from high-speed steel with a bright uncoated finish, this bottoming tap features an M8 x 1.25 metric coarse thread size and a D6 thread limit, making it suited for close-tolerance thread forming in ductile metals. The bottoming chamfer allows threading to the bottom of blind holes where clearance is minimal. Overall length is 2-15/16 inches with a 1-1/4 inch thread length and a 0.318 inch shank diameter. It is installed by machinists and maintenance technicians in production and repair environments.

This tap is used in applications where a threaded insert, such as a wire thread insert, is required to restore or reinforce threads in softer base materials including aluminum, cast iron, and mild steel. The M8 x 1.25 STI profile produces an oversized internal thread to accept a standard-pitch helical insert that restores to a nominal M8 x 1.25 thread. Typical install scenarios include automotive component repair, aerospace MRO work, and general manufacturing where thread stripping is a common failure mode. The recommended 75 percent thread drill size for pre-drilling is 0.354 inches.

Key Features

• Thread forming design produces no chips, reducing clogging risk in blind holes
• Bottoming chamfer allows threading close to the base of a blind hole
• M8 x 1.25 metric coarse STI thread profile for helical insert installation
• D6 thread limit for consistent, close-tolerance thread production
• High-speed steel construction for durability across a range of ductile workpiece materials
• Bright uncoated finish; Series BXMSTI

Compatibility

Designed for use with M8 x 1.25 metric coarse helical thread inserts (STI applications) in the BXMSTI series. Pre-drill with a 0.354 inch drill prior to tapping.

Installation Notes

This tap is installed by machinists or maintenance technicians using a tap wrench, tapping head, or CNC machine with appropriate feed rate control. Always pre-drill to the specified 0.354 inch diameter before tapping, and apply cutting fluid suitable for the workpiece material. Ensure the workpiece is securely fixtured and the tap is aligned square to the hole before applying torque. For blind holes, carefully track depth to avoid bottoming out and breaking the tap.