Captive nut question

[Jmac]

Ok fellas , the captive nut in the chassis rail on my Audi 80 is stripped due to the bolt being pulled through when it was damaged. Now the captive nut is meant to be 10mm metric but is around 12mm with some slop. No more room to go up a size there either. What do you reckon with helicoiling it??? i am shaking my head at it but i know there is differetn grades like inconel and the likes, my thoughts were that helicoils can pull with load. This captive nut is for a subframe bolt. Only other option is to cut the rail open and weld in a new nut and that is ELM St really.
What are your thoughts
CHeers
Jmac

[h100vw]

Helicoil if you have the gear, weld another if you don't.
I reckon its a Westonsuper.... not ELM St
Gavin

[Jmac]

Yeah i can get a helicoil mate but what do you reckon with it being a subframe mounting hole????? its one of 4 mind. To weld it it means cutting the chassis open and welding a nut then stitching it back up. Just a little bit concerned about the tension and strength using a helicoil, but mind you the aerospace industry uses them hey
Yeah a Weston super hahaha you got it mate
Cheers
JMac

[Peter Jones]

The recoil inserts claim to be stronger than the original threads. I use the M8 and M6 coils all the time for thread repairs, never pulled one out yet.

Pete

[Jmac]

Yeah Peter they say that mate, and im liking your confidence . Just got that feeling it being the chassis, but hey im going for it.
Let you know how i go
Cheers for the input
JMac

[roccodingo]

Installed correctly the heli coil will be fine. make sure when your tapping the thread out that you tap it square to the bore.
.

[jdrose]

the heli coil will be fine. they use them to refit head bolts, which have upwards of 40 foot pound of pressure om them. i have had nothing but good experinces with helicoils

[brad]

I've used helicoils for sparkplug holes & head bolts.

When I worked in the aircraft industry the structures guys used ..... /thinks really hard.....

keenserts - apparently they were superior to a helicoil.

but I also recall they used something called a cherry rivet. (but maybe that was to hold in a nut plate)??

Sorry I can't be any more help, I was a Production Planner & just pointed at things & said "Fix that".

[Golf Loon]

I`d open a flap in the chassis rail from above, weld in a new nut and then stitch it back down. If it wasnt a subframe, I`d use a helicoil.

[Preen59]

the heli coil will be fine. they use them to refit head bolts, which have upwards of 40 foot pound of pressure om them. i have had nothing but good experinces with helicoils

Yeah but its all load in one direction.. Helicoils aren't good with axial load.

I'd go keysert or recoil. Hacking the rail open and welding in another captive nut is a big pain in the a-hole.

I've had good experiences with keyserts, aslong as you have the meat around the hole to drill and tap it large enough.

[Jmac]

Funny as well as being a tech i was a structural tech with Boeing for 5 yrs. Spent 3 yrs with the FA18 here in Williamtown Newcastle, never used or heard of Keyserts. Anyone got a pic of an example or a source where i can get on from?? I agree with the load bearing issue thats why im being a bit hesitant. I was going to helicoil it today but held back till im truley satisfied in my head and qiute frankly im not at the moment. Been there before with Loons idea. Had a MK2 stripped and we opened up the rail and welde in a new nut. Total pain in the Ahole. How is the Keysert installed? i take it would be interference fit and yes there is loads of meat on the rail too. My old Foreman at Boeing is my best mate so ill be giving him a ring only thing is Boeing is all imperial man
Cheers
Guys
Jmac

[Preen59]

http://mdmetric.com/pdf/keysert.pdf

[Preen59]

How is the Keysert installed?
Jmac

You drill the hole to tapping size and tap it (obviously)...

Then you wind the keysert in by hand till it's flush with the top.

And finally, using a small hammer (and a pin punch if you want..), you tap the keys down into the parent metal.

The keys lock it in place without putting load on anything. And they're super strong.

[Jmac]

Ah yeah sounds good ill look into that mate. Loads of parent metal to play with. At the end of the day if all else fails i will use a tried and tested method i used on aircraft structures - Oversize bush couple of thou oversize then use liquid nitrogen to freeze and insert bush. So really having that there is tons of parent metal i could fit a say 22mm freeze plug giving you a fresh chassis rail so to speak then you can take it back to 17 0r 19mm worst comes to worst hey. Ill be looking at the keyserts 1st
Cheers again
Jmac

[Preen59]

Ah yeah sounds good ill look into that mate. Loads of parent metal to play with. At the end of the day if all else fails i will use a tried and tested method i used on aircraft structures - Oversize bush couple of thou oversize then use liquid nitrogen to freeze and insert bush. So really having that there is tons of parent metal i could fit a say 22mm freeze plug giving you a fresh chassis rail so to speak then you can take it back to 17 0r 19mm worst comes to worst hey. Ill be looking at the keyserts 1st
Cheers again
Jmac

All sounds pretty good to me.

Glad to help. I'm sure i'll have a question one day that you'll be able to answer..