Helicoils!!!! (Removal from deep holes)

[Mononeuron]

Hi Guys,
I'm wondering if anyone out there has a good method of removing worn out or stripped helicoils that are down inside a deep hole, typically deeper than 4 times the dia, where you can't get a pair of pointy nosed pliers into the hole to extract the offender..

The method I currently use, and is by far the quickest one I have found so far, is to use a small dia long tapered drift with about a 3mm dia end ground to a chisel point and a flat blade 8mm screwdriver with a slot ground into the side of the head with a 1mm cutoff blade from an angle grinder and at a small angle to act as a hook. The screwdriver is still usable as a screwdriver.

I use the drift to pop out one side of the Helicoil so you have a little tail projecting out into the hole and then use the slot in the screwdriver head to slip over the "tail" of the Helicoil you just freed and pull out the worn or broken piece. Usually takes about 30 secs from start to finish.

How do your methods stack up? I would be interested to find a better method.

My current field is underground mining equipment and a lot of the stuff I work on is helicoiled Aluminium parts.

Richard.

[Eaglewood]

I use a tool sold by Helicoil. It is just a flat blade sharpen on an angle to dig into the first thread. Easily home made. Just grind the angle(10 degrees or so) so the edges dig in when rotating ccw.
Dick

[NortonDommi]

As above plus a flat blade ground with a small spike on one side that can fit down side of above tool to pick out leading edge of insert to stop it digging in. Does not need to be bent out much. A stout ground down hook from a hook & pick set can work too.

[Jonny]

Removing helicons with the Helicoil flat blade is the first step. Failing that my approach is to grind a small chisel and drive it in-between the Helicoil and the old thread. Then pry the end out to where it can be grabbed with a plier. From there pull the old helical out stretching it and leading it away from the parent thread in order to save the base thread as much as possible. By pouring straight out the base thread will be cut more than necessary , thereby weakening it.
Helicoil also makes oversized helicoils to repair holes that have had their I.D.'s enlarged by this extraction method.
Be persistent and good luck.
Jon

[Mononeuron]

We have some 16mm Helicoils that are over 100mm deep inside the hole as the wonderful miners keep pulling off the front end of their feed rails and we need to drill and tap deeper and deeper to keep repairing to $56K feed rails. The hole depth is governed by the depth of the drill and tap we have on hand so pliers are out of the question after about 50mm in. That's where the slit in the side of the screwdriver comes into it's own. Makes it rather easy.
Rich.

[NortonDommi]

Have you considered new miners? Failing that is there sufficient material to put in a large diameter hardened insert? Something that threads are less likely to pull in?

[Stokestack]

I have the same task, to remove a failed helicoil from a spark-plug hole in a Mustang Cobra engine. It's 8 inches down a narrow well and inaccessible to pliers.

My main concern is getting the thing out intact, because I can't have metal fragments falling into the cylinder. This is what I'm dealing with:



I don't know the origin of that weird fragment at the 3:00-4:00 position, but it's attached to the coil (the shinier metal at the center of this mess). It might provide some purchase for rotating this thing CCW, and for hooking it with the kind of tool you guys described.

In your experience, do the coils stay intact if you pull them straight out by the end? I'm not concerned with the threads in the hole, because I need to tap it out to install a Time-Sert.

Thanks!

[Mononeuron]

Hi Stokestack,
You can make a wedge shaped tool from flat spring steel with a T handle like the bought ones and push that into the coil and try to unscrew it or If you can pop out the end of the helicoil then you can cut a slot in a screwdriver (slightly backward facing) and get hold of the end and pull the coil straight out. the helicoil always comes out in one piece so no problems there. Then just tap out the thread to clean it up and then insert another helicoil.
Rich.

[Mononeuron]

That fragment looks like an old piece of the sparkplug sealing washer. Never seen one break up before so I may be wrong.

[Stokestack]

Hi Stokestack,
You can make a wedge shaped tool from flat spring steel with a T handle like the bought ones.

Thanks! I've seen those, but of course the handles are way too short. I don't have a grinder, so making the metal wedge is already a problem, let alone mounting it in a handle.

I have a really long spade drill bit of the right width, which I could sand the little spikes off of with my belt sander (yep, I do have that). Not sure how I'd secure it in a handle; I guess I could make a wooden handle and put a couple of set screws in it. I'd rather not ruin it (it's handy for drilling through walls to run network cable and whatnot), but I suppose it's not too expensive to replace.

As for the fragment, I'm baffled as to when it appeared. The repair was done at least 10 years ago, but I didn't have misfiring until a few months ago; nothing was done to the engine immediately beforehand. The original diagnosis was bad plug wires, so I replaced both the wires and plugs. On reinstalling the wires, I noticed that the plug boot on the afflicted cylinder didn't sit flush against the valve cover the way the others did. Thus I suspected that the plug wasn't screwing in all the way, and the mess inside the well supports that theory. I think cylinder contents have been leaking around this plug; I checked the neighboring well and it's nice and clean.