Page last updated July 17, 2008



Bolt Hole Rethreading with Helicoil

The method behind the madness

Helicoil offers a method to repair stripped threads by creating a slightly bigger hole than the original using a tap and then inserting a spring like device that accepts the threads from the bolt. The resulting threads are stronger and should be the same size as the original.

When you purchase the kit, it should come with the coils, thread driver, drill bit and tap. You can also opt for the threads themselves if you already have the kit.

In order for this work, you need to ensure the hole is the recommended size for the coil that you are using. remember, the hole will be slightly bigger than it was before because you are essentially drilling out the stripped threads and then creating new ones.

Common tools needed

pic of stripped thread hole drilled out clean with recommended size drill bit.

Use cutting oil and keep the hole level and true to the original angle.


then, using tap and T-Bar, tap new threads where according to recommended size. The tap will actually be bigger than the original becuase the ccoil has to in and then the old size bolt, hence the need for a slightly bigger tap.Wear your safety glasses.




Blow out excess material every half turn with compressed air. Use cutting oil to make the process easier


When you have finished and are satisfied with the work, you can go forward with cleaning the old threads free of material and get the helicoil ready.



Use the included coil driver. It has a built in stop that will allow you to screw the coil in place. When the coild will not advance any further into the hole, remove driver. You can break the stop at the bottom of the coil with a screw driver. Simply tap it and it will snap allowing the bolt to go in further past the last thread of the coil..


Driver with heli-coil going into hole. Screw as far as you can go, but not so deep that the bolt will not catch.


Driver coming out with heli-coil in place. Test the coil with a new bolt to ensure proper fit. If you followed the manufacturer recommendations, it should fit without a go on and do mmore good.



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