16 replies to this topic

[skoughi]

So whilst fitting the transfer casing onto the gearbox to check idler endfloat I managed to strip the threads of two of the 5/16 UNC holes in the gearbox casing. So straight away I'm thinking to buy a helicoil kit, but could I simply bore out and tap for 3/8 UNC instead for these two bolts? What are the negatives for doing this?

[Alex_B]

I would say go for the helicoil, it will, if installed correctly, provide a stronger fix than merely a tapped hole in ally. It will also allow you to keep all the same size fixings which is much nicer than a random assortment! 

[nicklouse]

Helicoil. It will give a better wearing thread.
You will not have to drill out the transfer case.

You won't have gasket issues.

[skoughi]

Cheers Alex, this is what I'm kinda thinking. Found out some prices for helicoil and recoil kits and I think I can stretch to the £15 odd for these. I suppose going for the next size up has been done plenty of times to get out of a fix but as you say I'll end up with a stronger fixing and all the same original size bolts.

[skoughi]

Love recoils!! Located some locally today and replaced the two that was damaged, then felt it was sooooo easy I fitted another nine that was in the kit. Now I'm thinking to order some more and do all the ones in the gearbox casing and the transfer casing as well!

[ChopperHarris]

Why, do you intend to strip those as well? ;o)

[jaydee]

If done properly its not a bad idea, no chance of stripped threads and leaky gaskets

Sump plug hole is another weak point where an helicoil will help, shame the size (5/8 UNC) isnt cheap.

[Cooperman]

On aircraft engines it is not permitted to have steel bolts directly into tapped aluminium holes. In all cases a Heli-Coil is required, so to do them all is really a good idea.

[Itsjustanestate]

Helicoil every time. It really annoys me when I see a steel bolt threaded straight into to aluminium. 

[skoughi]

I have to admit that I got these as a freebie so to get enough inserts to do the lot will end up being a cheap job and will eliminate any possible problems with stripped threads in the future. If a stripped thread in an alloy casing can be a possibility then it'll happen to me!

[David128]

question??? how do you do a blind hole?

[skoughi]

What do you mean by a "blind hole" David?

[skoughi]

Why, do you intend to strip those as well? ;o)

Knowing me probably!

[David128]

blind hole.. not straight through . no exit.

[peter-b]

Same way, you might need a modified tap depending how close to the bottom of the hole you want helicoil. Some instances you can drill original hole deeper. I buy the long helicoils and cut to length if required. You can leave the driver tang on if it's not in the way.