Broken Bolt Extraction - Welding on a Nut

ElectroPulse · Apr 12, 2026

I'm 2 for 2 on stuck bolts in engine mount brackets whenever I've gone to do a timing belt. Had occasion to do the timing belt on my Saturn Vue this week, and been having some "fun" with one of the bolts.

The last bolt getting the engine mount bracket off felt different. It would turn, then bind. Did the ol' out-an-eighth-turn, back-in-a-quarter-turn thing for a bit until it finally broke off nice and deep in the hole (used PB Blaster, but given how far in the threads are, it was probably not reaching them).

Ordered some Mayhew Pro straight-flute extractors. PB Blaster'd it for a few days while awaiting their arrival. This afternoon I went out there and hit it with a torch for a bit, then 10-15 seconds with some Freeze Off, and hammered the extractor in. Wouldn't budge - now I've got a broken-off extractor added to the party.

Many of the videos I've seen of people removing stuck bolts, they end up getting them out by welding a nut on. Ran across one where they used a thin copper tube as a sleeve to keep it from sticking to the aluminum on the sides of the hole, so they could build it up from deep in the hole. Looks to be a good excuse to finally get a MIG welder, so ended up ordering a Primeweld.

Going to stop by the local tractor supply company this week and see if they have uncoated nuts. That aside, what is everyone's thoughts on MIG vs. flux core for this use? Also, what wire and settings do people typically use? (in the videos, they just whip out the MIG gun and get started, no discussion about settings other than "turning it up"). Lastly, any reason to be concerned about the broken-off extractor in there? I assume this is a "steel is steel" thing and just weld it in there (if anything, I figure the heat will make it lose its temper, so maybe easier to drill out if I get to that point).

Thank you

Xti04 · Apr 13, 2026

So for this application heat and wire speeds dont matter much. You are trying to fuse a nut to a 10mm bolt so it will need some heat. I have seen people put a copper washer over the broken bolt to prevent aluminum damage. Since you are dping a v6 honda belt there, I also suggest replacing the idler pulley bolt for the timing belt. Those break for some reason when reused. Run a thread chaser thru it to clean out the thread locker first.

strutaeng · Apr 13, 2026

I've always done flux core for this. I prefer it since it provides more heat vs mig for the same settings. And obviously appearance weld doesn't matter. Lol

I've used the little cheap 120V inverter welder (mine is the Century brand) with good success.

ctandc72 · Apr 13, 2026

Personally I think it's the heat from the welding that actually breaks everything loose - that's my WAG. How deep is that hole? I remember having one where I had to stack nuts. We ended up using a washer + nut + washer + nut. It took a few tries before it finally came out.

SusKatCas · Apr 13, 2026

I have had good success with the weld method on a number of projects. However, I have not used it on one broken off this far into the hole. I too have seen videos where a piece of copper tube was used to protect the base metal.

I have used both 0.035" ER70S-6 MIG wire and 3/32 6011 stick for removals.

For a 10mm and larger bolts, there is benefit to a little swirl once you strike the arc. I think this is best practiced on the bench with a couple donor nuts.

It may take a couple tries. I like to put a flat washer down first, consider one with a 9mm hole so you protect the edges of your hole.

Cheers, Alan

joe_padavano · Apr 13, 2026

Molten steel isn't going to "stick" to aluminum. In any case, I've had pretty good luck welding through the hole in the nut to get to the bolt. Your problem here is likely galvanic corrosion, which means you had better get a heli-coil kit as well.

JeepYJ · Apr 13, 2026

@zkdiesel

stickshift · Apr 13, 2026

And this is why I hate extractors, especially small diameter extractors. You waste a lot of time drilling to fit the extractor, only to have the extractor snap.

As someone suggested earlier, practice with a couple of nuts first. If you use too high settings or move too slowly, you can distort the nut so much that a socket won't fit on it (but don't be afraid of getting the nut glowing red). You want to get good penetration into that extractor and remaining bolt, then connect the small pile of weld from this step to the inside of the nut.

JeepYJ · Apr 13, 2026

stickshift said:
you can distort the nut so much that a socket won't fit on it

If you get something connected to the broken part inside the threaded hole you can always weld a much larger nut over the distorted nut. It’s better to have a good solid weld connecting everything rather than worrying about messing up the nut.

ctandc72 · Apr 13, 2026

joe_padavano said:
Molten steel isn't going to "stick" to aluminum. In any case, I've had pretty good luck welding through the hole in the nut to get to the bolt. Your problem here is likely galvanic corrosion, which means you had better get a heli-coil kit as well.

Here's hoping it's not that bad. This is a Ford small block water pump bolt FYI.

zkdiesel · Apr 13, 2026

Just lay a 1 size to big nut over it and burn it in hard

No copper needed, you won’t hurt allukinum enough to ever matter.

rattle_snake · Apr 13, 2026

I've has mixed luck with weld-a-nut. Even with enough heat to almost melt the sacrificial nut, the nut breaks off with enough torque. Depends on the specific situation, how stuck the broke off bolt is. Most of the time it is not my stuff, but I get signed up to fix it.

Rockable · Apr 13, 2026

Tig welding will get more heat into the fastener and you can control the amount and rate of adding filler.

Brianf60 · Apr 13, 2026

I have good luck with placing washer over the hole and going in fat and hard with Mig. I have never tried with flux core, only gas Mig.
your hole looks very deep but I think at this point you have little lose. How deep is it? I do t think I have had any that much more 5/16” below the surface.

MoonRise · Apr 14, 2026

I have never failed to extract the broken bolt/screw/stud from the hole it broke in when I've welded a nut to the remains. Crossing my fingers that I didn't just jinx myself.

Sometimes it has taken multiple welding attempts of the nut to the remains, but the process has always eventually worked for me. I think that my record was near a double digit number of nuts and welding attempts.

I've always used MIG. But I haven't had to deal with the broken shank too deep in the hole. More than about one diameter deep or more than about 1/4" deep and I'd reach for the stick rod instead though.

Although the steel electrode won't really 'stick' to the aluminum, the welding arc can still ****** up the threads. Aim carefully.

Speaking of aim, aim the arc/electrode at the center of the shank remains and THEN swirl (if needed) to the nut ID. If you get the arc/electrode to the nut ID first, you probably won't fuse to the shank well or at all. And you really won't get the arc heat into that shank either. And it is the heating-expanding and then cooling-shrinking cycle that mostly seems to be what helps loosen the stuck remains from the hole. The nut welded onto the end just gives you a place to grab onto. Which is pretty important after all.

As mentioned, I usually use about one nominal size larger nut than the thread diameter. Metric or SAE doesn't matter, use whatever. I'm just going to reef on that nut with a wrench or vise-grips anyway.

And once you get the remains out of the hole, let everything cool off completely and then chase the internal threads to true them up. Or use a thread insert if needed.

stickshift · Apr 14, 2026

OP, this is not an easy weld task for a first time welder. But good thing is you can try over and over. Don't inhale weld fumes, especially since you'll likely be using zinc plated nuts. You could soak the nuts in vinegar to remove the zinc, but realistically, most aren't going to do that for this kind of task.

ElectroPulse · Apr 14, 2026

Thanks for the replies, all!

Been thinking about it, and given how deep the hole is, does anyone have any recommendations of malleable, non-metallic sheet material I could cut and put around the wall of the hole to keep the electrode from coming into contact with anything but the bolt at the bottom? Not touching the sidewall is gonna be a tricky game of Operation given the depth.

ctandc72 said:
Personally I think it's the heat from the welding that actually breaks everything loose - that's my WAG. How deep is that hole? I remember having one where I had to stack nuts. We ended up using a washer + nut + washer + nut. It took a few tries before it finally came out.

It's just over 3/4" deep... gonna be a pain trying to get it in there.

joe_padavano said:
Molten steel isn't going to "stick" to aluminum. In any case, I've had pretty good luck welding through the hole in the nut to get to the bolt. Your problem here is likely galvanic corrosion, which means you had better get a heli-coil kit as well.

Do the threads in the parent material tend to get destroyed by galvanic corrosion? Also, does heat break apart galvanic corrosion the same way it does regular rust?

Rockable said:
Tig welding will get more heat into the fastener and you can control the amount and rate of adding filler.

The hole is too deep for that (a bit over 3/4") - even if I were to have the tungsten hella extended, there wouldn't be enough room to get the rod in there beside the torch at the entrance of the hole.

MoonRise said:
I have never failed to extract the broken bolt/screw/stud from the hole it broke in when I've welded a nut to the remains. Crossing my fingers that I didn't just jinx myself.

Sometimes it has taken multiple welding attempts of the nut to the remains, but the process has always eventually worked for me. I think that my record was near a double digit number of nuts and welding attempts.

I've always used MIG. But I haven't had to deal with the broken shank too deep in the hole. More than about one diameter deep or more than about 1/4" deep and I'd reach for the stick rod instead though.

Although the steel electrode won't really 'stick' to the aluminum, the welding arc can still ****** up the threads. Aim carefully.

Speaking of aim, aim the arc/electrode at the center of the shank remains and THEN swirl (if needed) to the nut ID. If you get the arc/electrode to the nut ID first, you probably won't fuse to the shank well or at all. And you really won't get the arc heat into that shank either. And it is the heating-expanding and then cooling-shrinking cycle that mostly seems to be what helps loosen the stuck remains from the hole. The nut welded onto the end just gives you a place to grab onto. Which is pretty important after all.

As mentioned, I usually use about one nominal size larger nut than the thread diameter. Metric or SAE doesn't matter, use whatever. I'm just going to reef on that nut with a wrench or vise-grips anyway.

And once you get the remains out of the hole, let everything cool off completely and then chase the internal threads to true them up. Or use a thread insert if needed.

Hmm... Stick hadn't occurred to me, since all the videos I've seen have used MIG or flux-core. Might be a bit easier to line up, given the access I have to the hole. When I took a TIG welding course a number of years back (never tried MIG or stick, and haven't touched TIG since that course), I saw some of the students learning stick having trouble with getting the rod stuck to the material, so am wondering how tough it'll be given the access. I'll look up some videos on it. The welder I've got on order can do stick as well, so that's certainly on the table.

stickshift said:
OP, this is not an easy weld task for a first time welder. But good thing is you can try over and over. Don't inhale weld fumes, especially since you'll likely be using zinc plated nuts. You could soak the nuts in vinegar to remove the zinc, but realistically, most aren't going to do that for this kind of task.

Thanks for the advice! Great tip on soaking the nuts in vinegar, I've had a little trouble finding plain, uncoated nuts so far. I'll look into that route if I come up empty on that front.

joe_padavano · Apr 14, 2026

ElectroPulse said:
Do the threads in the parent material tend to get destroyed by galvanic corrosion? Also, does heat break apart galvanic corrosion the same way it does regular rust?

Yes, corrosion can and will damage the threads and any other adjacent metal. The "breaking apart" with head comes from differential thermal expansion, which may help or may not in your case. Aluminum expands about 3x more than steel at the same temperature, so that may help break the corrosion, but at the end of the day, don't be surprised if the threads in the aluminum are messed up.

OccupantRJ · Apr 14, 2026

Too late for that here, but I had a bolt break deep in a thick timing cover once. The body of the bolt was bonded to the cover. Since I was removing the timing cover anyway I made a drill bushing on the lathe, then used that to drill a pilot hole close to the depth of the parting line between the parts. After that I drilled with the proper size to eliminate the bolt. After the cover was off it was a simple task to remove the remaining threaded part of the bolt with “normal” methods.

nadogail · Apr 14, 2026

I have found that Left Handed Drill Bits have been a good addition to my "Bag of Tricks"

M.Brane · Apr 14, 2026

Sometimes you got to get medieval on stuff:

oldtractors · Apr 14, 2026

From your description, the bolt is galled to the block. Basically welded to it now. Heat isn't going to help like it will for a corroded bolt. The correct step would have been to drill out the bolt and retap with or without a helicoil. But now, you have a broken off never-out in it as well that is too hard to drill. Maybe you can get the easyout out by welding a nut to it. Then you can drill out the rest of the bolt. Welding a nut to a easy out deep in a hole is probably not a good first project for a new welder to learn on. If you can't get the easyout out, then you might have to drill it out with a solid carbide bit, which has to have a very rigid setup. Like in a mill. How attached are you to the car? Sorry, but I am not optimistic about the outcome.

BTL-A4 · Apr 14, 2026

nadogail said:
I have found that Left Handed Drill Bits have been a good addition to my "Bag of Tricks"

+1 on this. Everytime I read one of these threads there's usually someone that's successfully used a LH drill bit to extract a nut. You havea a deep hole, so this seems like a good case to use a drill bit. Good luck, whatever you do!

stickshift · Apr 14, 2026

oldtractors said:
If you can't get the easyout out, then you might have to drill it out with a solid carbide bit, which has to have a very rigid setup. Like in a mill.

Yeah, drilling out an extractor (consumer grade extractors are often high carbon steel) with a hand drill would be miserable.

Beerhippie · Apr 18, 2026

I learned a lesson about the "weld a nut on it" trick yesterday. Had a broken-off bolt in an aluminum housing. The area around the bolt was sloped relative to the bolt axis. I welded a nut on there and broke off the bolt even deeper as the nut was resting on the sloped surface and cammed the bolt right in half with a half turn.

Shim the nut before welding so it's level with the axis of the bolt you're extracting!

Lassen Forge · Apr 18, 2026

Wait! Why futz around, when it's the ideal opportunity to add an EDM to your shop tools...
I *almost* pulled the trigger on a used one a few years back after fighting a similar stuck tap (grrr) but fortunately for my wallet I was able to get it out. But yeah - Tap Burners are amazing tools...

rust in the eye · Apr 18, 2026

ctandc72 said:
Here's hoping it's not that bad. This is a Ford small block water pump bolt FYI.

Cringeworthy words

stickshift · May 5, 2026

@ElectroPulse any updates on this?

ElectroPulse · May 7, 2026

stickshift said:
@ElectroPulse any updates on this?

Not quite yet - haven't had any time until the last couple of days, so it's just been sitting out in front of my garage.

Ended up tracking down my TIG welder I'd bought years ago and never used. It has stick functionality, so haven't ordered a MIG welder yet. Figured I'd try welding a nub onto the extractor, and pulling it out with pliers (it's a strait flute extractor, so jiggling it enough should get it out). From there, I was going to try to increase the hole size until I could try and chip the bolt out (then, failing that, drill it out larger and install a helicoil).

I've never stick welded before, so messed around with it a bit this evening on some coupons. Even horizontally, with a 1/16" rod, I wasn't able to get a nub that wasn't larger than the end of the extractor, so that idea's out.

Been reading tonight, and sounds like there are some stick welding rods that are made for this use, and they have thicker flux to help prevent the arc from straying out to the sides. Thinking about getting some of that and trying to fill it up, to weld a nut on it. From there, if that doesn't work, will probably try drilling the welded portion out, use a carbide burr or Rescue Bit to get rid of the extractor, and resume with the drilling the bolt out (and probably end up with a helicoil, if I get to that point).

Anyone see any issues with this idea?

SusKatCas · May 8, 2026

There are much smarter people here than me on this topic.

1/16" stick electrodes are not real easy to work with. Which one are you using? I have used 6011 and 6013. 6013 was ok fo some sheet metal work with no access to a MIG. The 6011 was miserable because it seems to burn back so fast when I used enough current to get a stable arc.

Just thinking out loud here. You might try deliberately sticking the electrode to the stub of the extractor. I've never tried to stick a rod on purpose. I would start with about 70 amps on a 1/16th electrode experiment with starting to strike the arc and immediately bury the rod in the puddle. Timing will be touchy.

Practice this on a bench before you try on the real parts. You could start with a a coupon to get your "poor mans stuff welder" timing down and then mock something up with a stud sitting below flush in coupling nut.

Cheers, Alan

ElectroPulse · May 8, 2026

SusKatCas said:
There are much smarter people here than me on this topic.

1/16" stick electrodes are not real easy to work with. Which one are you using? I have used 6011 and 6013. 6013 was ok fo some sheet metal work with no access to a MIG. The 6011 was miserable because it seems to burn back so fast when I used enough current to get a stable arc.

Just thinking out loud here. You might try deliberately sticking the electrode to the stub of the extractor. I've never tried to stick a rod on purpose. I would start with about 70 amps on a 1/16th electrode experiment with starting to strike the arc and immediately bury the rod in the puddle. Timing will be touchy.

Practice this on a bench before you try on the real parts. You could start with a a coupon to get your "poor mans stuff welder" timing down and then mock something up with a stud sitting below flush in coupling nut.

Cheers, Alan

I was using 6013.

Hmm... Good thought on deliberately sticking it to the extractor, I hadn't thought of that. It came off pretty easy when I accidentally did it to the coupons, but that was with some twisting (would definitely be stronger pulling straight up). Might even be able to go up a size or two with the electrode since it'll just be sticking it to it. I'll think about this while awaiting a chance to revisit.

I did get a set of long-reach diamond burrs ordered last night, as I'm thinking about trying to grind grooves on either side of the extractor to get the tips of some thin-tip pliers in. Thinking I might try that first, then go with sticking the electrode to it if that doesn't work out (and if testing on the bench looks good).

Broken Bolt Extraction - Welding on a Nut

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