The profile of the holding thread is regulated in the DIN standard ( DIN 8140 1-3).
For the production of a holding thread a special tap is necessary. In the German standard one speaks of EG thread, the international designation is STI thread. STI stands for Screw Tap Inserts. There are different types of taps to produce a holding thread: Hand tap set with pre-cutter, center tap and finish tap or single tap with long gate. For thread repair, we recommend the GSR single-cut tap for the insert thread. It has a 3-4 thread gate and is sufficient to cut a full holding thread. In addition, you will need a holding tool for the square of the tap. Adjustable tap wrenches or tool holders with ratchets do a good job here.
These two tools are necessary to assemble the wire insert. They are made of tool steel. The insertion tool has a powder-coated handle and an adjustable cap nut. The threaded wire insert is mounted on the insertion tool and then screwed in. The tang breaker is burnished, has a knurled shank and a flattened head. It is used to break off the threaded tang.
The most popular sizes for thread repair are M6, M8 and M10, as well as M10 x1, M12 x 1.5 and M14 x 1.5.
It was invented by the US Americans in the 1940s. It became known in Germany under the trademark Helicoil. The market share of Helicoil in Germany was once so high that Helicoil became the generic term for this type of thread repair. In the meantime, these systems are offered under different brand names (Bair Coil, V-Coil). Since they are all based on a DIN standard, they are generally compatible with each other.
You can buy thread repair sets here in the store. Please ask for not so common sizes. We have a wide and deep assortment of other sizes in stock.
There are sets for single sizes ( e.g. M 6 ) and large thread repair sets for M 5 – M12.
Thread repair sets belong in every workshop in trade and industry.
Thread inserts and thread armorings are gaining more and more importance for additive manufacturing! You can find more information here:
Thread inserts/ thread armouring for 3D printing models
You can find step-by-step instructions in this article: 11 steps to thread repair