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Discussion Starter · #1 ·
I did it this time...went to install my new stator and the bolts kept spinning and spinning, check the bolts, and low and behold they had aluminum in the threads.
The top two holes are stripped.
IMG_20180525_204357_01.jpg

The issue as I see it is the amount of material I have to work with if I go with helicoil/making the hole bigger. Don't want to risk the metal cracking over time. I was told Devon made a solution I might be able to fill in the holes and make new threads with... any other options.
 

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Devcon would be similar to using JB Weld to fill the hole, drill and tap. It's said that this type of repair would be suitable for this situation but I'm hesitant to suggest that.
I would look at using a Heli-Coil for this repair. This isn't a part that's commonly removed, like spark plugs, or under fairly high torque, like head bolts, so the threaded insert should hold for the life of the engine fine.
The drill bit size is 6.2mm so there's not much metal removed before tapping for the insert.
 

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Heli-Coil is the only way to do this. Devcon / JB Weld is half-a$$ed and will strip out again. 1/4-28 drill and tap is workable, but now you've introduced standard fasteners. Don't worry about losing metal by drilling out for the Heli-Coil, there's plenty there. And the steel insert will never strip out. There's a reason that this is SOP on aircraft.
 

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Discussion Starter · #6 ·
Going with helicoil. Engineer family friend is fabricating a guide for the drill to make sure the holes are perfectly centered for the inserts. Thanks guys!
 

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Might also be a good idea to measure the depth of the existing holes (can be done with a paper clip or the like) and then marking the drill so that you don't go farther than the depth of the existing holes. This will also be useful in determining that there's enough depth for the Heli-Coils to fully insert. Finally, on a blind hole application like this, remember that the Heli-Coil tap is tapered- the last 1/4" or so of its length doesn't cut any threads. If the hole is, say, .4" deep, and the Heli-Coils are .375" long, you'll need to run the tap in as far as it'll go, but then use a bottoming tap of the same thread pitch and diameter to run the threads all the way to the bottom of the hole. A bottoming tap can be cobbled by grinding the tip off of a regular tap of the desired size and lightly chamfering the tip, but remember that you must always start the threads with a regular, tapered tap.
 
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