Baer Heli Coil Tap - Wire Thread Insert - Bottoming Tap (STI) - Metric - M39 x 4 is the precision tool you reach for when threads break down and need a robust reinforcement. Engineered for durability and accuracy, this tap delivers clean, true threads that accept coil inserts with confidence, restoring strength where it matters most.

Why this tap stands out

• Oversized design for coil inserts: BaerCoil STI taps are manufactured oversized to accommodate the wire thread insert profile, ensuring reliable engagement and consistent thread quality. This dedicated specification helps you achieve durable repairs that last.
• High-speed steel, built for repeated use: Crafted from HSSG (high-speed steel, ground) to withstand the rigors of shop environments and maintain sharp cutting edges through multiple jobs. This translates to longer tool life and fewer replacements.
• Bottoming geometry for full-depth threads: The bottoming design cuts threads all the way to the bottom of blind holes, ensuring the coil insert seats fully and bolts thread in smoothly. This is the standard approach for STI bottoming taps in the Helicoil system.
• Metric precision — M39 x 4: Specifically tuned for metric threads, this tap creates accurate M39 x 4 profiles that align with common component specifications and Heli-Coil inserts.
• Part of a trusted thread-repair ecosystem: Designed to work with wire thread inserts to restore original thread strength in damaged holes across aluminum, steel, and cast iron applications.

Who benefits most

Ideal for automotive technicians, machinists, aerospace maintenance crews, and serious DIY enthusiasts who demand durable, repeatable thread restoration. If a hole has been stripped or damaged, this tap helps you recreate the precise threading path necessary to reclaim full fastening strength and reliability.

Practical use cases and outcomes

• Repairing stripped studs and bolts in engine blocks, cylinder heads, and transmission housings where load bearing is critical.
• Reinforcing soft metals like aluminum to prevent future stripping under repeated torque.
• Restoring critical threads in machinery housings and structural components to extend service life without replacement.

How to use (quick guide)

1. Drill the correct pilot size for M39 x 4 threads in the target hole.
2. Use the bottoming tap to cut full-depth threads to the bottom of the hole, ensuring proper coil-seat depth for the insert.
3. Install the Heli-Coil wire thread insert with the matching installation tool, then verify smooth engagement with the mating fastener.

The Baer Heli Coil Tap is the trusted choice when you need durable, precise thread repairs that restore original strength and function. It’s the tool professionals reach for when every bolt matters.