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how can I remove these badly corroded screws?

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  • how can I remove these badly corroded screws?

    First, the pics:

    This is a socket head cap screw that's been threaded into aluminum for at least 20 years, many or all of them outside. Galvanic corrosion no doubt is to blame, but as you can see the screw head is completely and hopelessly stripped.



    Now let me zoom out so you can see the problem. These screw heads are mostly down in a pocket of sorts.



    Two of these four screws were intact enough to remove by hammering in an alan wrench and then hitting it with a hammer. Then they unthreaded. These two - forget it. Stripped clean out.

    I need some suggestions as to how to remove them. Here are some observations: the screw heads are extremely corroded and I am skeptical I can weld anything to them. Normally I'd drop a little square of sheet metal over, weld the screw head to the sheet metal, then put a larger nut over all and weld that to the sheet metal and then turn the big nut with a wrench. But there's no room and like I said I don't think a weld will hold.

    I can try to drill out the sockets, the goal being to remove the heads entirely so I can get the C face adapter off of this right angle head, leaving the (much less corroded) threaded parts sticking out about an inch. Those I could work with. I really hate to try drilling freehand - I seem to be terrible at it. Plus, I'm right handed and I broke my right elbow about 3 weeks ago so I can't really do a ton of forceful work.

    I could try sticking an air hammer's chisel directly on the side of the socket head and rattling away and see if I could pop the head off.

    Any other bright ideas?

    metalmagpie

  • #2
    any way to mount the whole thing to a mill and plunge cut the heads off the bolts?

    I've had some success step drilling seized bolts until I'm close to the thread crests, then the leftovers usually screw out, but it's a pain, hard to center the drill sometimes and you have two of them to do (= twice the pain).

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    • #3
      I would mill off the socket heads and pull the adapter off , but before that I would try to slot the heads with a Dremel Abrasive disk and use a screw driver to see if
      I could budge the fastener . Slot deep so you get material under the socket cavity
      Rich
      Green Bay, WI

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      • #4
        Sorry to hear about your elbow. I was thinking the same thing Rich was about slotting the heads, however I would use my pneumatic cut off tool with a three or four inch disk. It would make a wider slot, and if a screwdriver wouldn’t turn them out you may get them loose with a chisel and hammer tapping against the slot on one side. I’ve had good luck with Kroil.

        Jerry

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        • #5
          Eat them out with alum? just like removing a broken tap.

          You might first try banging in a torx tip and using an impact driver to remove. Little splines tend to bite in the hogged out allen head.
          Last edited by lakeside53; 05-27-2021, 12:33 AM.

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          • #6
            If the head size happens to match one of this sort of sockets I'd attempt to remove them with impact driver.
            https://www.amazon.com/Topec-5-Piece.../dp/B086H9Y2K3 (different sets and sizes available)
            https://www.amazon.com/REXBETI-Impac...7W91Y3LQ&psc=1

            Hammer the socket over the bolt head and start slowly with impact gun and alternate with hammering the socket deeper on the bolt head.
            Location: Helsinki, Finland, Europe

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            • #7
              You could try using this stuff: https://www.amazon.com/Aircraft-Scre...productDetails

              Apply a couple of drops, hammer an Allen or Torx driver into the head. Whatever grip the driver gives, this will greatly increase it.

              First time I saw it (around 1995 or so), I thought it was snake oil - it looks like grinding paste. One actual go at using it quickly changed all that - it's as if someone just TIG welded the driver to the fastener, I now keep the stuff in my toolbox.

              Ian
              All of the gear, no idea...

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              • #8
                These problems are usually best handled by proper preparation, soaking with Aerokroil, impact driver, etc. Now you'll have to mill or drill out the screw heads.
                12" x 35" Logan 2557V lathe
                Index "Super 55" mill
                18" Vectrax vertical bandsaw
                7" x 10" Vectrax mitering bandsaw
                24" State disc sander

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                • #9
                  I agree with soaking with a penetrating oil of some sorts first (PB Blaster is easily available by me). Then drill (either hand drill, if reversible, or machine) with a left-handed bit for pilot hole. Then try an "easy-out" (screw extractor bit) in a large tap wrench for leverage.

                  Doesn't always work, but mostly does.
                  Sometimes the LH bit will grab while drilling and unscrew it on its own.
                  Last edited by MyrtleLake; 05-27-2021, 08:03 AM.

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                  • #10
                    Originally posted by metalmagpie View Post
                    [snip]
                    ...the goal being to remove the heads entirely ...
                    This should be pretty easy: cut-off wheel in a die grinder.

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                    • #11
                      I worked with a fellow who had a knack for regrinding drill bits so that they would cut in reverse, and dig deep into stuck or corroded bolts, quite often he was successful at first try. Depending on your skills at freehand drill grinding it might be worth a try. Regards David Powell.

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                      • #12
                        I would try a left hand drill. Allen bolts are often hardened so may not work. Before that I would try a torx driver driven in, then vice grips, then probably try and weld something on, maybe a bar straight out the side to break it loose. Just weld along the top edge and break it off after.

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                        • #13
                          Originally posted by lakeside53 View Post
                          Eat them out with alum? just like removing a broken tap.
                          That was my thought, too. Bang off as much of the rust as possible and dunk the whole thing in a hot water alum bath and let it rip. Never tried it with such a large bolt, though... I'm sort of curious how well it would actually work.

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                          • #14
                            Heat the bolts red with the TIG torch.
                            Let them cool.
                            Repeat at least 10 times, 20 is better.
                            They will almost fall out after this treatment.
                            Anything less is just playing around.

                            -Doozer
                            DZER

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                            • #15
                              Originally posted by Doozer View Post
                              ...Heat the bolts red with the TIG torch.
                              Let them cool.
                              Repeat at least 10 times, 20 is better.
                              They will almost fall out after this treatment.....
                              Yeah, heat would be my first weapon of choice in a situation like that. Mechanical methods
                              always leave you with the risk of breaking the head off and making things worse. I'd use an
                              oxyacetylene torch with a smallish tip; heat the head red hot and let it cool. Do it a couple
                              times and then cool everything down with cold water then repeat a couple times more and try
                              gripping the head with vise grips and turn it out. Whatever method you use to grab the bolt
                              I don't think there's a hope in hell of getting it loose without some heat...


                              Keith
                              __________________________
                              Just one project too many--that's what finally got him...

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