Stripped Bolt hole for rear shock

[mattd]

Originally Posted by Trav
Not to be a **** but whats is with these time serts? They are no stronger than heli coils in fact they are in many cases weaker at 4 times the price.
They are the best thing for things that need to removed many times over the life of the product eg spark plugs, oil pan drain bolts and the like. They are specified for spark plugs and some aluminum applications because the insert is also aluminum and the heat transfer is the same for the insert as the base metal, aluminum expands much more than steel and consequently the coil could loosen, the plug heat range is also not effected.

This aluminum expansion is the reason valves in an aluminum head tend to get more clearance when at operating temps not tighter like an iron head.
They are not a replacement for a heli coil in every application, just an additional tool to do a proper repair.


It was just a suggestion. But you seem to know best so carry on. Shocks should be changed just as often as spark plugs so that is a poor example. If done properly it should last the life of that control arm.

 

[Trav]

The control arm is not subjected to combustion chamber temps so no need to take thermal expansion into account.
The other point of why a coil is not the best for plug repair is on most you need to break a tang off (definitely not cool in the cylinder) unless you buy tangless coils.

 

[sky]

Here are the better pictures from today. The spot on the other side is pretty tight. I haven't tried to put a wrench or anything in there.

 

[spasm3]

Seeing those pics, i'd almost be inclined to find the correct size bolt that fits through the shock eye. Get the correct length bolt ( grade 8 ) so you can cut the head off, and insert the bolt and weld it into the hole leaving the threaded end as a new stub for the shock, then use a nut and washer from the open side of shock. Might have to drill the threaded end a bit .

I'd run this idea past Trav, since he is the expert here.

 

[sky]

Originally Posted by spasm3
Seeing those pics, i'd almost be inclined to find the correct size bolt that fits through the shock eye. Get the correct length bolt so you can cut the head off, and insert the bolt and weld it into the hole leaving the threaded end as a new stub for the shock, then use a bolt and washer from the open side of shock. Might have to drill the threaded end a bit .

I'd run this idea past Trav, since he is the expert here.



Welding is where it gets beyond me. I don't think I'm able to do any type of welding at all nor am I trained to do so...

 

[Trav]

This is an easy one, there are many approaches to this, none are wrong just some easier and cheaper to do than others.
I would just use the tap you have and run it through, take the same diameter size bolt as original just longer (make sure the shoulder is not longer), put a washer and nut on the new bolt from below as it is coming through.

Or heli coil the thing, either is quick and easy. I don't think I would be welding it in though just my opinion. Welding bolts subjected to stress may diminish the bolts heat treating, if it breaks with use that is a bit bigger of an issue. Whatever you do you need a hardened bolt in this application.

 

[whatnext]

It looks like you can get a nut and wrench up inside the shock mount structure. If you can, the simplest fix would be to drill out the remaining thread in the mount so a new bolt will pass thru. Then bolt the shock in using a nylok nut and washer = done.

 

[sky]

Originally Posted by Trav
This is an easy one, there are many approaches to this, none are wrong just some easier and cheaper to do than others.
I would just use the tap you have and run it through, take the same diameter size bolt as original just longer (make sure the shoulder is not longer), put a washer and nut on the new bolt from below as it is coming through.

Or heli coil the thing, either is quick and easy. I don't think I would be welding it in though just my opinion. Welding bolts subjected to stress may diminish the bolts heat treating, if it breaks with use that is a bit bigger of an issue. Whatever you do you need a hardened bolt in this application.


Alright, so the thought now because getting a helicoil is going to take at least 3 weeks per Amazon, Keep using the same tap I was using earlier and then just completely destroy the threads? I think the challenge is to find a hardened bolt My home depot doesn't seem to have anything in stock. I'm going to check it again. The bolt is an M12 so I guess I should find the same size one.

 

[sky]

Originally Posted by whatnext
It looks like you can get a nut and wrench up inside the shock mount structure. If you can, the simplest fix would be to drill out the remaining thread in the mount so a new bolt will pass thru. Then bolt the shock in using a nylok nut and washer = done.


Alright, this is what I was asking and clarifying and didn't see the reply. Thanks

 

[whatnext]

Check this:

The tube on the shock where the bolt passes thru, might go inside the diameter of the mount and seat on a land (I think I see it in your early picts). If it does, make sure you don't damage the land when drilling out the remaining threads.

Make sure you can get a nut and wrench up inside the mount.

(Helicoils and others are elegant fixes but unless you are experienced with installing them, I would have a shop do it. If there is a land in the mount for the tube on the shock, that will prevent drilling out the diameter to fit a helicoil)

 

[Trav]

Either the tap you were using or the smallest drill you can fit in there that will just remove the rest of the threads, if you do go with a coil you don't want it too oversize.

 

[Trav]

Originally Posted by spasm3
Seeing those pics, i'd almost be inclined to find the correct size bolt that fits through the shock eye. Get the correct length bolt ( grade 8 ) so you can cut the head off, and insert the bolt and weld it into the hole leaving the threaded end as a new stub for the shock, then use a nut and washer from the open side of shock. Might have to drill the threaded end a bit .

I'd run this idea past Trav, since he is the expert here.


Spasm, this may interest you.

https://www.portlandbolt.com/technical/faqs/welding-high-strength-anchor-bolts/

FWIW Due to the high shear factor this bolt is subjected to, thread pull out isn't as big a concern as bolt shearing. A 10.9 or 12.9 should be used. On the lighter rear of the car you may get away with an 8.8 but its not ideal and definitely not up front with much more weight/stress loading.

 

[sky]

Originally Posted by Trav
Originally Posted by spasm3
Seeing those pics, i'd almost be inclined to find the correct size bolt that fits through the shock eye. Get the correct length bolt ( grade 8 ) so you can cut the head off, and insert the bolt and weld it into the hole leaving the threaded end as a new stub for the shock, then use a nut and washer from the open side of shock. Might have to drill the threaded end a bit .

I'd run this idea past Trav, since he is the expert here.


Spasm, this may interest you.

https://www.portlandbolt.com/technical/faqs/welding-high-strength-anchor-bolts/

FWIW Due to the high shear factor this bolt is subjected to, thread pull out isn't as big a concern as bolt shearing. A 10.9 or 12.9 should be used. On the lighter rear of the car you may get away with an 8.8 but its not ideal and definitely not up front with much more weight/stress loading.



Yea, I'm trying to source a 10.9 or 12.9 bolt for this application. I've gotta head to the hardware store probably tomorrow or so to see if they have something like this. When I was there yesterday, the bolts they had weren't 10.9 and I believe they were just partially threaded.

 

[spasm3]

Originally Posted by Trav
Originally Posted by spasm3
Seeing those pics, i'd almost be inclined to find the correct size bolt that fits through the shock eye. Get the correct length bolt ( grade 8 ) so you can cut the head off, and insert the bolt and weld it into the hole leaving the threaded end as a new stub for the shock, then use a nut and washer from the open side of shock. Might have to drill the threaded end a bit .

I'd run this idea past Trav, since he is the expert here.


Spasm, this may interest you.

https://www.portlandbolt.com/technical/faqs/welding-high-strength-anchor-bolts/

FWIW Due to the high shear factor this bolt is subjected to, thread pull out isn't as big a concern as bolt shearing. A 10.9 or 12.9 should be used. On the lighter rear of the car you may get away with an 8.8 but its not ideal and definitely not up front with much more weight/stress loading.



Thanks Trav , makes sense. That kills my idea.

 

[sky]

Originally Posted by Trav
Either the tap you were using or the smallest drill you can fit in there that will just remove the rest of the threads, if you do go with a coil you don't want it too oversize.


Well - I don't know whether or not if this is a turn of events. I wandered into the local hardware store and they have Grade 8 SAE bolt. Out of pure curiousity, I bought a 7/16 inch bolt that's slightly longer than the original and it actually started to thread into the hole. I added a washer on one end and then i'm going to add a washer/nut on the other end. This is one of the most... interesting fixes. Thoughts? I didn't helicoil or do a time-sert. Those kits are coming later this week and I can probably return them.

What is everyone's thought about bolt size? The original is 12mm, this is 7/16, which is about 11.1mm. Any risk here?

 

[sky]

 

[Imp4]

Originally Posted by sky
This is one of the most... interesting fixes. Thoughts? I didn't helicoil or do a time-sert. Those kits are coming later this week and I can probably return them.

What is everyone's thought about bolt size? The original is 12mm, this is 7/16, which is about 11.1mm. Any risk here?

I think it's a pretty bad idea to use a bolt from the wrong thread system on a stripped out threaded connection.
Especially on a suspension component.

The risk is that the bolt will loosen over time due to vibration and then either fall out or fail.
If you are unwilling to drive it with no bolt in there, you should also be unwilling to drive it with the wrong bolt in there.

 

[sky]

Originally Posted by Imp4
Originally Posted by sky
This is one of the most... interesting fixes. Thoughts? I didn't helicoil or do a time-sert. Those kits are coming later this week and I can probably return them.

What is everyone's thought about bolt size? The original is 12mm, this is 7/16, which is about 11.1mm. Any risk here?

I think it's a pretty bad idea to use a bolt from the wrong thread system on a stripped out threaded connection.
Especially on a suspension component.


Is this any different if I drill out the rest of the threads and put a bolt through and a nut on the other side? Mechanical/material engineers welcome, but I was taking some advice of folks here. I think that's why I'm asking.

 

[Trav]

That will be fine, no problem once you get the washer and nut on.

 

[whatnext]

If you are thinking of saving the remaining threads, the different bolt size will ruin the remaining threads. If you are going to bolt it up like you described with a nut and washers, that would be the easiest fix that will work. But use a nylok nut to ensure the bolt doesn't loosen. To the concern of shear loads on the bolt using a 7/16 grade 8 (valid concern), I would just keep an eye on the bolt head for any obvious shifting (sign of overloading the bolt). If you are still concerned about using a grade 8, order the stronger stuff and replace the grade 8 when it comes in.