Re-threading lower wishbone U bracket captive nut ! HELP !!

youngsyp

New Member
Cut a long story short, I need to get the above re-threaded/ taped/ helicoiled. It's the nut right up inside the body that secures the U bracket that holds on the rear of the lower suspension arm. Has anyone done it ? And could they give me some advice ? I have tried re-threading it with the correct tap but, the bolt just pulls out with any torque on it. I'm gonna try SE Nisstek to see if they can do it.

Thanks chaps.
 
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jasegould

Guest
This prob wont help but when I worked at Vauxhall there was a prob with some of the captive nuts inside the chassis, we used to have to cut the floor open and reweld the nut, then refit the floor......and this was on reasonably new cars aswell.

What you could do is re tap it to the next size to take a larger bolt.
 

youngsyp

New Member
Thats what I am looking at as a last resort. The access is fairly good so, I'm confident it can be re-tapped and helicoiled. I could do it myself if I had a car lift. Unfortunately, the nut is and m12 and I don't think there is such a thing as an m13 so it would have to be an m14. So, this could be the second resort.
 
A

AZ STE

Guest
The bolts have a fine think 1mm pitch metric thread. Initially I would try rethreading the same M12 but course thread (using a corresponding bolt) this should give you enough new thread to tighten onto.When your tapping it make sure you use a tapping compound so you get good threads without breakage. If this doesnt work an imperial thread of say 1/2" UNF would be worth trying
 

youngsyp

New Member
The thread is 1.25mm pitch. A special by all accounts. I thought of this but, wasn't sure if it woud work. I re-threaded with the same pitch tap but, when I applied a decent amount of torque to the bolt the thread collapsed on the nut. It is now booked into SE where I was going to get them to helicoil it. Do you think it would be wise to ask them to re-tap it with a coarser, say 1.75mm pitch first ?
 
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AZ STE

Guest
Its better to go back to the finer thread if your helicoiling more surface area contact for that particular job
 

youngsyp

New Member
That is what I would do, go back to the original thread. Which I think is the best option anyway. I don't think going to a coarser thread would be any good, as it is still the same diameter so, would have nothing to 'bite' into.
Thanks for the advice. :D
 

Websnowbo

New Member
I’d have a good think about this before you do it because M14 is pretty big to go if it is a captive nut, I’d say too big. Also Nuts are made of Shite material that bears more resemblance to iron when you tap it so the chances of getting a Helicoil to hold is pretty impossible.

The best bet is to replace the nut even if it means cutting a small hole into the floor (You can tack weld it back later) or maybe go for a near imperial size, ½” is what you will need to do that.

Oh and make sure you drill it straight!!
 

youngsyp

New Member
The nut is definitely made of stronger stuff than iron. It has chewed up several good quality bolts. I agree with the m14 idea though. The torque placed on the nut whilst drilling and tapping it out will be immense and probably finish it off ! I'm happy with the helicoil idea from the research I have done. The nut will be taken out to about 13.6mm, if I recall, then tapped for the helicoil. Another idea would be to weld a stud in there if all else failed !
 
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