Heli-coil vs. Larger Diameter Bolt?

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Zoomy
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Heli-coil vs. Larger Diameter Bolt?

Postby Zoomy » Mon Mar 16, 2015 11:17 am

I don't have any experience in this department so am wondering what people think. The 4 bolts on my rear end carrier housing are 10mm in diameter and are threaded. Two of the holes are damaged due to my having over torqued the threads (the housing is aluminum) and therefore are now stripped. I can feel the rear assembly moving up and down slightly when I step on and lift off of the accelerator. So now I am faced with having to repair the damage. This is where the question comes into play.

Should I drill the holes with a slightly larger diameter bit and install heli-coils and use the same 10mm bolts, OR, should I drill all 4 holes to a larger diameter and use a tap to establish new threads and install 12mm bolts?

Note: the current carrier housing has ample material in which to enlarge the hole and install 12 mm bolts. I guess I just question that if there's enough material there then why didn't they (the engineer's/designers) use 12 mm bolts to begin with to hold the housing in place especially if it is subject to the torque force of the driveline during acceleration? It seems to me that the 12mm bolts will hold better than the heli-coil but the effort to repair will be more extensive.
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Pitcru
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Re: Heli-coil vs. Larger Diameter Bolt?

Postby Pitcru » Mon Mar 16, 2015 6:03 pm

Hi Carl, I have had some experience in similar issues. Go the Heli-coil route and you should be fine. A small amount of blue Loctite won't hurt either. We used to heli-coil brand new submarine parts from the start to prevent problems like this. Good luck.

Mark
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Zoomy
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Re: Heli-coil vs. Larger Diameter Bolt?

Postby Zoomy » Mon Mar 16, 2015 8:42 pm

Thanks Mark. I'll give it a try. I guess if it doesn't work then I can resort to the other method.
~ #155...'07 2.4L Supercharged Solstice
Thumpshit...a repetitive noise one hears when hitting cones.

"I had more fun and was more scared in the Pontiac Solstice" ~ Vanhtha Souvannasing [in response to ride alongs during the Bill Dodge Open House Drifting/Autocross Day]

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DM
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Re: Heli-coil vs. Larger Diameter Bolt?

Postby DM » Wed Mar 18, 2015 1:44 pm

I've also had great success with helicoils in aluminum, they work great and you get the benefit of the steel threads for reuse. If you think about it you do drill the holes out for the larger thread size, you just fill the space with the hardened steel insert
Dan

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scruffy
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Re: Heli-coil vs. Larger Diameter Bolt?

Postby scruffy » Thu Mar 19, 2015 9:10 pm

What Dan and Mark said. If you drill for a bigger bolt and strip out then you may not any material left. Coil is steel on steel threads.
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