Botched helicoil repair

Mitch81special

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Hi everybody, so iv got myself in a pickle. I was attempting a helicoil repair a valve cover stud. I neglected to use a non-tapered tap and when I installed the helicoil it followed the now tapered threads and essentially I have a tapered helicoil. So I'm thinking if i can remove that helicoil without damaging the new threads then i can grind the taper off my tap, finsh the job and reinstall a new helicoil. My question is how do I go about removing the helicoil? Iv seen the special arrow head shaped tool that grabs and twists them out but I'm worried that this coil is so tight in there because of the taper that might not work. Also seen a video of a guy just picking one thread out then peeling the whole thing out like a slinky. Any tips greatly appreciated.
 
No guarantees, coz I've not done it meself, but when I took a Triumph rocker box to an engineer to ask about a Helicoil, he just grabbed the end of the insert with a pair of needle-nose pliers and pulled it out. The insert kind of unwound as he pulled - probably what you meant by like a slinky?

I suppose you have the extra reassurance that you intend to re-tap the hole in any case . . .

Edit - crossed in the post with Machine.
 
I would try to grab one of the top threads with a pair of needle nose pliers and gently rotate CCW it should twist out if you're patient and gentle. I would then start over with a Timesert or EZ-LOK insert.
 
I've done it both ways, depends on how deep you've threaded the coil in.
Technically you're supposed to turn it in till the end of the coil is fully engaged in the tapped hole which makes it more difficult to peel the coil out.
If you have a scribe or other sharp pointed tool you may be able to get the end picked out enough to grab with needle nose pliers.
The "arrow" pointed tool also works, you just need to be careful to place it so that the edge is as far from the coil end as possible, especially in softer material like aluminum. If not you might cause the coil end to bite into the base metal and raise a burr which will make it difficult to turn the coil out. It also helps if when you insert the tool into the coil you rock it back and forth so the tool edge cuts into the coil a bit for a better bite before you try and turn it out
 
You would normally use a taper tap to start with and if required follow that with a bottoming tap where the cutting part goes to the bottom of the tool.
This will cut the tread to within the last 1 to 2 turns of the thread.
 
I've done a couple on the valve covers using a standard tapered bit. First I probe the hole for depth and then mark the drill bit with a bit of tape so as to not drill deeper, but consider the end taper in your measurements as the insert "no go" area and drill accordingly. The heli-coil insert is a fraction of the depth and it just needs to be below the finished surface. Once set to the desired depth the tab is broken off allowing the bolt to travel past the coil.
Mistakes can be unwound as stated above.
 
With some patience you should be able to get it out. Maybe shoot some oil in the hole to keep things moving. I’m a bit puzzled about the tapered tap. All my helicoil taps are more like bottoming taps meaning they are fairly square shouldered at the end. Good luck with the extraction.
 
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Helicoil is square cross section wire, wound to shape. Timesert is a solid bushing.

Time-Sert-VS-Heli-Coil1.jpg
 
They do make Heli-Coil bottoming taps. I have the M6 sized one and have used it several times, including on a valve cover stud repair.
 
Is there a problem here at all ? .. Am I a bit far out here perhaps ??
Perhaps something I have Misunderstood.
There are conical threads at may places piping fex
As i Understand it the pre tap has been used and not the bottom tap making the bottom end of the hole conical
Not fully threaded
But if you insert the stud wont it bottom out against the conical hole and and sit tight .
If careful and keeping the torque in check
The pin shall not be removed ... Or ??
and if worried perhaps making the pin conical with an angle grinder.
This depends on how it looks and how far in the pin goes and the H coil is in
pin sticking out.and so on
as a rule of thumb the same Thread length as the nut can be good.
And this being a place where the pin never shall be removed
And if careful tightening and loosening the cover perhaps it is OK
 
Thanks for the input everyone. I managed to successfully remove the helicoil by peeling it out. I then grinded my tap to a bottoming tap and finished tapping the hole.
Some comments make me think people think this stud hole is deeper than it is. It is only as deep as the post and the helicoil isn't much shorter than that. And I was unsure about drilling any deeper than the factory hole.
20210408_162252.jpg
 
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