Removing bad helicoil

[Brad Smith]

Encountered problem number 368 last night while re-assembling my RF-94, a bad helicoil in the gearbox adapter. It is installed on a slight angle and the very end is sharp and stopping the bolt from threading. I have an oversize keen sert to replace it, if I can remove the old helicoil. Any advice on how to remove the old helicoil?

[KevinFirlein]

have you tried using a pick like tool and just unthread the coil ? Lift the end closest to you and just let it unwind. That will do the least amount of damage to the existing whole. Its what I do when I get a car that I am redoing and it has a bad or crooked heli coil in it. Just make sure it truely is a heli coil as they are very easy to undo and know once you start you are committed

[formulasuper]

Encountered problem number 368 last night while re-assembling my RF-94, a bad helicoil in the gearbox adapter. It is installed on a slight angle and the very end is sharp and stopping the bolt from threading. I have an oversize keen sert to replace it, if I can remove the old helicoil. Any advice on how to remove the old helicoil?

Is the Helicoil useable if you could get the bolt started? If so, I'd try removing the sharp end with a small rotary grind stone or similar device.

[Steve Demeter]

Make sure that when you drill for the keensert that you get the new larger hole square with the face on the adapter. Otherwise you will have the same problem and will not be able to fix it as easily.

Before I drill out for the keensert, I would remove the old helicoil if the sharp end can't be ground off and put a new one in correctly and see if the bolt starts then.

[Messenger Racing]

What Steve said.........

[Brad Smith]

Thanks for the advice. I will try to salvage the old helicoil tonight. I've been stuck at work on 12 hour shifts for 3 days.

[Randy Cook]

Good advice above. To avoid the situation in the first place:

In the tool box that contains my heli-coil sets there are, for each heli-coil set, two pieces of 1" round aluminum bar about 1 1/4" long, with through holes drilled axially in the center matching first the tap drill for each helicoil tap and the second one sized to guide the tap. I drill and face these square on a lathe and in use, hold the bar hard against the workpiece as I drill or tap the hole through the center hole of the bar. This is a way to be sure the drill and tap are run into the workpiece squarely. (Be sure to write/etch the size of the through hole and the thread it's to be used with on each of these bars.)

[Hawke]

Randy,

What a great idea. I've been putting in helicoils just off square for years now, but that is usually because I'm too lazy to pull the thing out of the car and do it properly on the bench.

[mousecatcher]

http://www.tapguide.com/shopdata/index.shopscript

[Rick Kean]

http://www.noblefix.com/helicoil/Hel...tion-Tool.html

Heli-Coil Extracting Tools at bottom of page (Note, not Extraction Tools)

Insert, Strike, Turn

Rick

[EACIII]

Was working on a large gas turbine rebuild project recently and one of the helicoils failed while torqueing down the upper case. Had to pull the unit apart again to repair the helicoil. Don't ask what that cost. That being said, make sure you get them installed right the first time.

Ed Callo