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Rounded Bolt Extraction - need help!

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Not sure if this is the right forum - feel free to move this thread if necessary.

I've run into a rusty bolt that I cannot remove. It has a rounded head and is recessed. I'm looking for advice on how to remove it.

See the attached photo. It's an M10 bolt (14 mm head size) fastening a cross-brace to the frame under my car. The bolt head is recessed into the cross brace so I need to use a socket or similar (wrench or vice grips won't work here). The head is rounded enough that all my 14 mm sockets slip very easily, but it's still too large for a 13 mm to fit. Closest SAE socket would be 17/32", which is not a standard size.

I've already tried using 2 different bolt extractors (the kind w/spring loaded pins and the spiral socket kind), but they didn't work. I also tried a hammer and chisel to "spin" the bolt, but because of the angle I don't think this is very effective. I got the chisel to bite into the head a bit, but it's not at a good angle. This might come in handy later.

Okay so the real question is what else can I use to grab the bolt head tight enough? Most online articles say to heat it up good then turn it with vice grips or similar, but that won't work here. I bought a torch so I'll try heating the bolt up to hopefully loosen it up (break the rust bonds), but I still need to grab the bolt to turn it after that. I'm not sure what else I can do here.

Some options I've thought of, but haven't tried yet. Would any of these work or just waste of time?

  • Can I somehow grind or chisel the bolt head to allow either a 13 mm socket or one of the extractors to bite better? E.g. chisel some detents into it and use a smaller socket? Not sure if this will help.
  • I could buy a sacrificial 13 mm socket and grind out the inside of it with a dremel until it fits snugly (effectively creating a 13.5 mm socket). Tough to do accurately.
  • Can I shim the inside of a 14mm socket somehow to make it a tighter fit? I would need some very thin steel bar or maybe stack some foil or steel wool, other material to create a better bite? Or similarly, could I fill the 14 mm with some JB Weld or Epoxy or something and let it set overnight to get a good fit on the bolt?
  • I could grind a slot into the bolt head so I could turn it with a flat head screwdriver, but I doubt I could get enough torque on it that way. Maybe after heating it up enough this would work.
  • I could weld on a sacrificial nut - well, not me, but someone could for me. I would need to ask a favour or take it to a shop. How difficult would that be since the bolt is recessed? Would one need a MIG welder or special skill to be able to do this?
  • My very last resort is to cut the brace off with an angle grinder or saw, then remove the bolt with big vice grips or something, but I really don't want to do that as the brace cost $$.

Any advice is appreciated!



Edited by Beau
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Filling a socket with JB Weld and letting it set on the bolt head for 24 hrs before trying to remove has worked for some people; however, don't just rely on the JB Weld to work through form fitting. Clean the bolt head as much as possible, so that the JB Weld also bonds to the bolt, not just to the socket.

I prefer the welding method. Clean the bolt head as much as you can, then hammer on and MIG-weld a M14 nut (or M13, if you have) onto the bolt head. The idea here is to plug-weld from the bolt head to the nut, thus heating up the bolt significantly while ensuring a solid mechanical connection between the bolt head and the nut. Do not compromise on the welding process: heat transfer into the bolt shaft is equally as important as a good connection to the nut (this is why you start welding from the center to the outside). Start removing the bolt immediately. This has worked for me as often as I have tried it.

Having said that, when I look at your picture I get the feeling that your bracket is not in a great shape anymore, anyways. It seems that around the bolt it starts de-layering. I would not be surprised that, once removed, you will find the bracket quite rusty around the bolt hole... you may still be looking at buying another one, anyways (or repairing this one).


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Drill the bolt head off. Remove bracket, then remove remainder of bolt. If the bracket is gone you should be able to grips around the remaining thread and remove it. If not, completely drill the bolt out, retap for new bolt.

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Thanks for the advice, guys. I tried for about 2 hours yesterday to no avail. :(

I tried grinding a slot into the bolt and using a 1" by 1/8" thick piece of aluminum bar as a very wide screwdriver but I just ended up twisting the aluminum. Yeah I know steel would have been a better choice, but I don't have any lying around. Anyway that tells me it's still stuck in there pretty good. I heated the bolt with a torch a couple times and tried again and still no luck. Used lots of PB blaster. I tried a couple bolt extractors including hammering them on first, didn't matter - they still spun. I now have a very round bolt head.

I also tried drilling it out from the centre, but that would take all night. I think I need better drill bits. I have a set of LH drill bits with "titanium coating" (crap) and all my standard bits are also the yellow kind (crap). I applied considerable force and barely made a hole in the bolt head maybe 2-3mm deep. A screw extractor couldn't even get started. I doubt it would work anyway, judging by how much torque is needed, so I'd probably break the extractor off if I got it to bite. Anyway, I gave up after 20 mintues of drilling upside down. Not worth it.

The central problem is still there - cannot grip the bolt well enough to apply enough torque. I will take this somewhere and ask them to weld on nut for me later in the week.

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You need cobalt drill bits...and you won’t need to go too fast...I’ve drilled out metric hardness 8.8, 10.9, and 12.9 no worries before.



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Welding a nut on is the way to go. Don't bother with extractors - you'll end up breaking it off, and they are hardened - thus very difficult to drill out.

Use as big of a nut as you can - you'll probably be limited by the bracket hole for the socket size. The larger nut ID will make it easier to make sure the weld has good contact with the bolt head.

Good luck!

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There's also the possibility that the bolt is so seized that it will break after getting enough torque from that welded nut. Plan ahead for that. i.e. Don't drive the car to a buddy's and plan to drive home that evening. 

Might be fine, might not. Plan for the worst. 

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The hole in the photo should have had a plug in it. The backside of the bolt is inside the chassis that you can likely access through that hole.  Spray penetrating fluid deep in there as well if you haven’t already.
That is a grade 12.9 bolt so it’ll be stupid strong and likely quite long. 

I have had to pull up carpet or panels to access the upper portion of the bolt. 


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  • 4 weeks later...

Update to close this thread.

I ended up using JB Weld to "glue" on a larger (M14) nut onto the rounded head. And it worked! :)

I ground down some of the internal threads on the inside of an M14 nut and then pounded it onto the bolt head with a hammer. I put JB Weld on the bolt head first, so it got "into" the joint, and onto the mating surfaces, and then filled up the entire nut with more JB Weld and let it cure overnight. I guess that heating up the bolt several times in my original efforts probably loosened it up because it actually came out fairly easily with the new nut. After it was out, I tested the JB weld joint to failure and it came apart at less than 50 ft-lbs, so take that for what it is. Below are some pics. 

Anyway, this might be an option for someone else out there who cannot weld and is stuck in a similar situation. It worked for me!


The bolt after extraction, showing JB Weld:




After testing to fail:


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