Stripped Thread at recovery Point Fix?

[Sheepy]

Hi All

It seems I have a stripped thread on the front of my KZN130 where the stock hooks were. I was snatched out of a bog and after when I was checking stuff I noticed the hook was bent, turns out it wasn't bent, just loose, I tried to tighten it but the bolt just spins. I have pulled it out and the threads on the bolt are fine, so assumptions says its the internal threads on the chassis.

Can I helicoil this, or would it be better to drill it re tap it the next size up? I would rather a hard but safe job over a easy but unsafe job when it comes to recovery points.

Whats my best option?

[mudlva]

Can you get inside the chassis at all?
Maybe by welding a suitable size flat ir round bar to a h/t nut and them using a longer bolt. You may need to open up the captive nut to suit the new bolt.

[Sheepy]

I dont know if I can, I don't think so, but ill wip the bumper off and have a look. So basically add a square nut inside the chassis yeah?

[mudlva]

yes just make sure its high tensil

[Sheepy]

Sweet, ill have a look tomorrow. In the event where I can't get into the chassis rail, what then? Any idea's?

[derk]

In the event where I can't get into the chassis rail, what then? Any idea's?

yeah if you cant bolt the hook on properly with high tensile 12mm 8.8 bolts and matching high tensile nuts don't bolt the thing on at all

[Craydiver]

don't weld a high tensile nut or bolt unless you really understand welding these materials
you will end up with a brittle layer at the weld interface, parent metal in the HT nut.
Subject to premature failure
you can weld HT, but you need plenty of pre heat

[Sheepy]

Cool. So in that case repairing the stock thread is a better option?

[Craydiver]

Im no expert on the stock nuts on these, but I would suspect if your've stripped threads that the nuts aren't HT (meaning a 8.8 or higher)
im unsure that the pulling would have stripped threads - technically the load is a shear on the bolt - not a tensile load on the threads
If your captive nuts are mild (ie equiv to a 4.6) I expect that you may have damaged the threads when these HT bolts were tightened on installation.
then the loading has loosened things off.

[mudlva]

don't weld a high tensile nut or bolt unless you really understand welding these materials
you will end up with a brittle layer at the weld interface, parent metal in the HT nut.
Subject to premature failure
you can weld HT, but you need plenty of pre heat

good point that, worth considering if its done properly tho

[Gardengnome]

Rather than welding a nut to a piece of flat. Drill and tap a piece of fairly thick piece of flat bar, Say 20mm thick or so. Thicker the better.

Drill and tap two holes the same spacing as the hook mounting holes and then slide inside the chassis.

You might need to do some work to remove the old captive nuts. Possibly also need to weld up and redrill the chassis to have a nice neat/tight fit for the bolts and stop the hook moving during snatching at angles slightly off straight.

[trucked]

Cool. So in that case repairing the stock thread is a better option?

If the threads are damaged i wouldn't recommend repairing them, replacing with something better is the best option.

You may have broken the captive nut off inside the chassis if its spinning.

Is your hook just attached to only two of the holes? if so that is again not the best idea, ideally you want to build a h shaped bracket to go between the chassis rails and bolt to all 6 of the holes and the ones under the rad, spreading the load away from captive nuts is a good idea as they have been known to rip out part of the chassis when only connected to two of them.

I made this when i did my winch bar this spreads the load to all the bolts available to me and allows the hooks to be up the right way.

It has 10 bolt holes that attach to the chassis

[Smurf]

Cool. So in that case repairing the stock thread is a better option?

If the threads are damaged i wouldn't recommend repairing them, replacing with something better is the best option.

You may have broken the captive nut off inside the chassis if its spinning.

Is your hook just attached to only two of the holes? if so that is again not the best idea, ideally you want to build a h shaped bracket to go between the chassis rails and bolt to all 6 of the holes and the ones under the rad, spreading the load away from captive nuts is a good idea as they have been known to rip out part of the chassis when only connected to two of them.

I made this when i did my winch bar this spreads the load to all the bolts available to me and allows the hooks to be up the right way.

It has 10 bolt holes that attach to the chassis

20130701_124335.jpg

This is a really good idea, lets you get the hooks up the right way too. I have a very similar bracket under the front of my Surf, although mine only catches 3 bolts either side. Garden Gnomes idea is good too if you can get the old captive nuts out