Thread Repair ( stripped)

[badgertom]

I recently stripped the threads for an 8mm bolt. I plan to fix the thread with a helicoil. Since the bolt is longer I was thinking about using two helicoils (one on top of the other). Probably one coil is sufficient, but would two be better? Also, is it possible to do this or would the bolt get stuck at the junction of the two coils? I have never heard of anyone doing this so I am curious as to whether it can or has been done. Thanks for any advice.

[lewellen]

I recently stripped the threads for an 8mm bolt. I plan to fix the thread with a helicoil. Since the bolt is longer I was thinking about using two helicoils (one on top of the other). Probably one coil is sufficient, but would two be better? Also, is it possible to do this or would the bolt get stuck at the junction of the two coils? I have never heard of anyone doing this so I am curious as to whether it can or has been done. Thanks for any advice.

How long is the bolt? M8 Heli-Coils go up to about an inch long....

I personally would avoid using two Heli-Coils. The way these things are inserted, the helices should line up for an inserted bolt ... but "should" and "will" aren't quite the same, and I could see getting some galling or abrasion as the bolt transitioned from one coil to the next. That could be bad ... especially if the bolt locks up and you wind up having to drill it out....

Since, to do this, you will need to drill out the original threaded hole and re-tap for the Heli-Coil, is there any possibility of simply going to a larger bolt size and having done?

Best,

- Lewellen

[motoracer8]

Rule of thumb, a threaded hole does not need to be deeper than the cross section of a bolt. stud, etc. Except in aluminum. A standard 3/8" or 10mm deep 8mm Heli coil will be ok as it will be stronger because of it's larger diameter.

Ken G.