Dec 99 - "Piggybacking"of Heli-Coil Inserts

"Piggybacking"of Heli-Coil Inserts

Occasionally, a specific application may arise where extended thread depth is required to support a significant load, thus requiring and insert length which is longer than any normally available.

In these instances, it is an accepted practice to "piggyback" two inserts to generate the extra thread needed. This is accomplished by drilling and tapping the hole to the required depth, installing the first insert to the bottom of the hole and breaking off the tang. The next insert should then be installed just to the point where it's tang touches the previously installed insert. The tang should then be broken off on this insert.

This process is most commonly seen when two free-running inserts are used but can be used in a screw-lock assembly. It is important to note that when a screw-lock assembly is being prepared, only one insert should be a screw-lock insert and the other a free-running insert. In this instance, it is also recommended that the free-running insert be installed first in the bottom of the hole and the screw-lock insert installed second.

For further technical assistance, please contact the Applications Engineering Group.

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