STI Machine Tap ISO 529 HSS-G - M 12 x 1.25

An STI Machine Tap is not an ordinary tap. The abbreviation STI stands for "Screw Thread Insert". It cuts an oversized thread into a pre-drilled hole to accommodate a thread insert (e.g., a V-COIL wire helix). The thread insert is screwed into the STI thread, creating a new, durable, and strong thread in the original nominal size (in this case M 12 x 1.25). This method is often used for thread repair or for strengthening threads in soft materials such as aluminum.

This model is suitable for use in well-machinable materials up to a strength of 900 N/mm², including unalloyed and low-alloy steels.

• ISO 529: This is an international standard for hand and machine taps with metric ISO threads. It defines the dimensions and tolerances, ensuring the tool's compatibility.
• HSS-G: Stands for "High-Speed Steel Ground". The material offers high hardness and wear resistance. The ground finish (G) ensures higher precision and a smoother surface, which improves the tool's performance and extends its life.
• Tolerance ISO 1 / 4H: This is the tolerance class for the cut thread. A 4H (ISO 1) tolerance is a tighter tolerance than the standard 6H tolerance. It ensures a very precise and tight fit, which is crucial for the correct function of the thread insert.
• M 12 x 1.25: This indicates the nominal size of the final thread. M 12 stands for the nominal diameter of 12 mm, and 1.25 is the thread pitch in millimeters. The actual thread cut by the STI tap is larger to accommodate the thread insert.

Follow these steps to cut a precise STI thread:

1. Preparation: Drill the core hole with the diameter specified in the V-COIL table. The hole must be clean and deburred.
2. Clamping: Securely clamp the STI tap in the machine or a suitable tap wrench.
3. Cutting: Cut the STI thread into the prepared hole. Use cutting oil to reduce friction and extend the tool's life.
4. Insertion: After cutting, the thread insert is screwed into the STI thread using the appropriate tool (installation spindle or insertion tool).
5. Finishing: The drive tangs of the thread insert are broken off with the tang breaker tool after installation. The finished thread now has the nominal size of M 12 x 1.25.

1. What is the main difference from a standard tap?

An STI tap cuts an oversized thread that is larger than the final thread to accommodate a thread insert. A standard tap cuts the final thread directly.

2. Can I use this tap without thread inserts?

No, the tap is specifically designed for use with thread inserts. The thread it cuts is too large for a normal M12 screw.

3. What drill bit size do I need for the core hole?

The core hole size is larger than for a normal M12 thread. The exact dimensions can be found in the V-COIL application tables, as they are crucial for correct function.

4. Can I use this tap for aluminum?

Yes, this tool is excellently suited for soft materials like aluminum, as it is used for repairing or strengthening threads in these materials.

5. What does the tolerance 4H mean?

Tolerance class 4H stands for a very tight tolerance. In the context of thread inserts, it ensures that the insert sits firmly and precisely in the thread.