Questions on using a mig to remove a broken bolt

Discussion in 'Engine Topic' started by mrluckies, May 13, 2020.

  1. mrluckies

    mrluckies Veteran Member Lifetime Gold Member

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    I’ve used a mig to remove broken bolts from a couple different engines in the past and had good luck with it.

    however this time it’s kicking my butt and I’m not having much luck. I don’t remember what welder settings I used last time and was wondering if you guys have advice?

    I’ve got a Lincoln Weld pak and this time I set it at the highest heat rating (D) and a feed speed of about 7. But for some reason I’m not getting the weld to stick to the broken bolt consistently. I’ve gotten good penetration twice and both times it broke off part of the bolt because it’s really stuck in there (the dreaded steel bolt in an aluminum head by exhaust).

    now the bolt is about 1/4” below the surface and I don’t seem to be getting it to stick anymore.

    I saw one video where the guy set his Lincoln on heat range B, one of the colder settings and a low wire speed of only 3 and had good luck. Could it be my wire speed/heat combination is filling the whole to quick?

    also, how long do you guys wait after welding before you try turning it out? I’ve done both cherry red and a couple minutes.

    finally, I have two exhaust studs that I used an oxy torch to heat up the nuts and get them off no problem. Do you think I should try and replace the studs while the engine is out or take my chances with new nuts and hope the studs don’t break when I reinstall it?

    If I should take them out, should I try heating the exposed part of the stud cherry red and wait a till it’s not red before turning them out?

    appreciate any advice.
     
  2. tom3

    tom3 Veteran Member

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    I'd probably go the hard way now and drill out that bolt. And try to clean the threads up on those studs and use as is if not rusted away bad. Can be a real mess getting them out even with heat. Be more drilling and retapping maybe.
     
  3. kenny77

    kenny77 Veteran Member Lifetime Gold Member

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    Here's the deal ,
    Whatever I weld with my MIG. I always get the best weld and penetration and results with a slower wire speed and about a med-high heat. The Wire Speed is to me the biggest factor on the quality of the weld. Heat is to me, more of a (Not too hot to burn through) setting if you know what I'm saying. .30 wire, and Stargon sheild gas should get that. Now I've done the bolt thing with both the MIG and the TIG
     
  4. mrluckies

    mrluckies Veteran Member Lifetime Gold Member

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    Thx for the info! I switched to a lower heat setting so I could use a slower speed and it definitely helped! Unfortunately, prior to your reply, I read somewhere about drilling a hole in it so it will shrink better and it wound up that I kept pulling only a thread of two at a time and leaving the rest. Even though I was barely turning it and slowly working it back and forth.

    I ended up drilling it out the rest of the way and now need a helicoil. I was close to center and a bolt will grab a few threads, but not enough for my liking.

    like i said, I’ve done it before years ago and know it works. Just couldn’t remember how it set up my gun.
     
  5. 1980RS

    1980RS Veteran Member

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    I used my mig welder last year to get some broken blots out of my LS heads on my truck. Tried lots of the ideas that people used on youtube, buy what worked was just kept building up one blob of weld on top of each other on the broken bolt then when it was not red anymore put a vice grip on it and the broken bolts came right out.
     
  6. tom3

    tom3 Veteran Member

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    Sometimes when you finally get the bolt out there are some threads left in the bottom, a bottomed out stud and nut will do the job for some things that don't need super strength.
     
  7. Pentupfury

    Pentupfury New Member

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    I have had very good luck using left handed Irwin drill bits to remove broken bolts that are below the surface. I measure the hole diameter closely and then select the drill bit diameter. Once I have these two dimensions I purchase a drill bushing to keep the drill centered in the hole. Typically while drilling out the bolt, it releases from the mating material before you ever get to use an extractor bit.
     
  8. Pentupfury

    Pentupfury New Member

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    IMAG0447.jpg
     
  9. KingofThings

    KingofThings New Member

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    Does this work on Grade 8 bolts? I have a conundrum in that I’ve had to have my new harmonic balancer on and off a few times. Because the old bolt was rounded over I replaced it. The seal in my new chrome timing chain cover has slipped out. In attempting to take the bolt out again I felt it binding up and figured it might break so I stopped and got it to torque properly for now. So now I’m thinking, grind off the bolt head, pull the balancer and deal with the bolt however necessary. Think spraying with Blaster might work alone or even with some heat and vice grips...anyone?
     
  10. Pentupfury

    Pentupfury New Member

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    I would first use some Kroil which is the best penetrate we have found. Look it up and order some. It's better than any blaster out there. I would try that first. Then perhaps look at other methods afterward.
     
    70-camaro likes this.

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