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Bought a TV recently. Tried to mount it onto our concrete block wall.
Drilled. Hammered the M8 wall anchor bolt (with the nut on) too hard and it morphed the bolt.

Struggled to unscrew the nut, ended up completely smoothing the thread so now I need to replace it but I can't pull the damned thing out :(

Yes I'm an idiot. Any suggestions from this lovely community on how to do it with minimal damage to the wall would be massively, massively appreciated.

Here's the bugger:

enter image description here

This is what it looks like out of the box:

enter image description here

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  • Using a big prybar(3foot/1meter or bigger) with a scrape wood plank to protect the cement might do it, if you can jam the opening into the threads. Putting some lube oil in the hole won't hurt either. If hollow wall blocks, just push anchor though the hole. Usually about 1inch/2.5cm thick.
    – crip659
    Commented Sep 26, 2021 at 22:38
  • Wait! Yes it is messed up but can you still hang the TV off of it? It is in there good, which is a valuable quality.
    – Willk
    Commented Sep 26, 2021 at 23:52
  • @Willk OP said he stripped/smoothed the treads. Might be able to fix threads with a tap and die set.
    – crip659
    Commented Sep 27, 2021 at 0:31
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    Grind all of them off flush. patch and move up or down an inch or two
    – Kris
    Commented Sep 27, 2021 at 1:55
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    I dont know why.. but i would probably end up putting my drill around that stripped thread and see if the bolt will turn.. if so, see if that frees the lug from the grip it has... ( not an answer.. but i just looks like it wants to be done). :)
    – Hightower
    Commented Sep 27, 2021 at 5:35

6 Answers 6

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Unfortunately, wedge anchors like that are intended to be permanent. It looks like there is a bit of the collar protruding; if you can manage to push the bolt into the wall and grip the collar well enough then you could possibly wiggle the collar out and then remove the bolt.

If it won't come out then you're probably looking at cutting or grinding it flush. The bolt may want to spin when cutting; if so hold it steady with locking pliers. Grinding could be done with an angle grinder or rotary tool ("Dremel"), but given this is in finished interior space, beware of the sparks. They'll damage glass and could be hot enough to smolder and ignite some furnishings.

On the chance you have or want to buy a carbide or diamond hole saw you could use one of these sized just larger than the collar and drill in a bit. The stripped-out bolt will work as a pilot. ;-) This would allow you to clear out some of the concrete on the outside of the collar, possibly giving you a better chance at grabbing the collar and pulling it out. Could even just cold chisel the concrete for that matter.. Either of these approaches will show that bolt who's the boss, but they'll leave you with more patch work and it's not certain the hole would be reusable anyway after removal of the existing anchor.

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Get yourself a pair of vise grips and get the bolt out first. The bolt pushes the wedges out to anchor the base into the concrete. Then you should be able to wiggle the base out. Your other option is a good carbide metal cutting sawzall blade to cut it off flush with the concrete.

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If the wall is hollow cinderblock, maybe you can hammer it in so it is flush with the wall.

Failing that, angle grinder.

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Take a metal cutting chisel and cut it flush with your wall, then patch with Portland cement. All done!

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    This doesn't help reuse the original bolt location.
    – isherwood
    Commented Sep 27, 2021 at 13:23
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Whatever you do will leave a mess.

A hole saw for concrete slightly bigger id than the od of the fixture will allow complete removal, but obviously you won't use it with the normal centre drill bit.

Depending on how swaged the outer tube is now, it may be possible to knock the bolt back in, so the tube can be wriggled out - dependant on the original hole size, its depth, and the amount of swage and whether there's enough protruding.

Angle grind off, deep enough to allow re-plastering, taking care not to splatter anything with sparks. A sheet of thin ply works well - check for ignition, though !

If it's actually in a good, usable place, die the thread again - may need to go one size smaller, when yu need to be sure it's still strong enough.

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  • Sometimes changing from SAE to metric dies is better size wise, than dropping a size in SAE.
    – crip659
    Commented Sep 27, 2021 at 11:54
  • @crip659 - good point, something I often do. However, both may well not be available in a particular country. Why would they sell imperial in Europe, for example? I'm lucky, Dad was an engineer and I have 100s!
    – Tim
    Commented Sep 27, 2021 at 12:46
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knock the stud back into the wall as far as it will go without deforming, then grab the edge of the sleeve with locking pliers and pull, once the sleeve is removed the stud will come out easily.

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  • This may well not work - the hole may not be deep enough, how do you know when deforming starts, and the sleeve wil already be deformed, which is why it's already stuck. -1. ( I try to justify dvs).
    – Tim
    Commented Sep 29, 2021 at 23:34
  • it usually does. the stem had to move to wedge the sleeve, so there's a void behind the stem. to avoid deforming the stem hit it with a soft hammer, or a wooden club. if there's grit particles that have fallen into the splits of the sleeve then yeah it will be hard to extract.
    – Jasen
    Commented Sep 30, 2021 at 20:52
  • When I fit these sort of fixings, I drill the hole just deep enough - often not as deep as you consider, so there's no wriggle room behind. Although it looks from the pic that the hole wasn't even deep enough...
    – Tim
    Commented Oct 1, 2021 at 7:38

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