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Thread: How to remove these countersunk bolts

  1. #1
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    How to remove these countersunk bolts

    I cannot shift these countersunk bolts, either by hand or with an impact driver.

    They hold a 12" sanding disc, by the way.

    SandingDisc.jpg

    Any advice on how to free them?
    They take a 5/32th hex bit.

    Thanks, Mark

  2. #2
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    If you can't turn them out you could drill the head off and then remove the plate. Just use a drill bit that's the same size as the threads. Use a good sharp bit and a little cutting oil and take your time.
    Confidence: The feeling you experience before you fully understand the situation

  3. #3
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    Are you using an electric impact wrench or one of these https://www.tequipment.net/Klein-Too...fa2d0371d4e04?

    I have had pretty good success with the manual type.
    Ken

  4. #4
    Quote Originally Posted by Jerry Bruette View Post
    If you can't turn them out you could drill the head off and then remove the plate. Just use a drill bit that's the same size as the threads. Use a good sharp bit and a little cutting oil and take your time.
    DO NOT DO THIS. A drill that's the same size as the threads will obliterate the internal threads. If you feel the need to drill any out, start with a bit the size of the hex socket. Increase the hole a drill size at a time. Eventually, the head will spin loose and the remaining threaded portion will usually spin out easily.

  5. #5
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    Quote Originally Posted by Ken Fitzgerald View Post
    Are you using an electric impact wrench or one of these https://www.tequipment.net/Klein-Too...fa2d0371d4e04?

    I have had pretty good success with the manual type.
    Definitely the way to go

  6. #6
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    A thread diameter drill will pop the head off. Once it spins, you stop, and don't remove the rest of the thread.

    If the disc is aluminum, there's some chance the black oxide screws have bonded to it. I've seen it on hard coated parts. Screw breaks loose with a crack and a puff of smoke. Smells kind of funny too. Aluminum oxide, iron oxide ... no clue what the reaction is.

    I had several that did this on a motorcycle sprocket.

    Flat heads are the worst. Lots of head area, teeny tiny socket. I wanna say 'you're sc....d', but let's be optimistic ;-)

    Drill the heads off, and hopefully there's enough to grab to remove them from the spindle. If they're loctited as well, you'll have more hassles. DO NOT TRY AN EASY-OUT!!!! Break that off, and you'll be looking for someone with an EDM.

    Smaller drill, as suggested, gives you a decent pilot hole .. just in case.

  7. #7
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    Quote Originally Posted by Ken Fitzgerald View Post
    Are you using an electric impact wrench or one of these https://www.tequipment.net/Klein-Too...fa2d0371d4e04?

    I have had pretty good success with the manual type.
    Those are incredibly effective. They'll remove Phillips head screws from a corroded old aluminum motorcycle engine, so I'm sure those bolts wouldn't be a problem.

  8. #8
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    I was in your exact problem with a sander bought at auction . Used a small high speed grinder with a tiny grinding wheel and cut a slot to fit a large flat blade screw driver with square shaft used vice grip on shaft broke free with very little pressure and got new flat head bolt and installed with anti-seize. Good luck

  9. #9
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    Thank you all for the wisdom - I like the look of Ken's Klein tool. I'd be keen to try that before I drill them or slot them with a Dremel.

    A friend offered to weld a short hex bolt onto the existing bolts and then wrench them off. He claims the heat will also help free them.
    Does that strike anyone as being feasible?
    He's a good welder, but I'd be concerned about damaging the disc.

  10. #10
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    MIG a hex nut directly to the screw. The heat of welding will loosen the screw and it will come out easily.

  11. #11
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    Quote Originally Posted by johnny means View Post
    DO NOT DO THIS. A drill that's the same size as the threads will obliterate the internal threads. If you feel the need to drill any out, start with a bit the size of the hex socket. Increase the hole a drill size at a time. Eventually, the head will spin loose and the remaining threaded portion will usually spin out easily.

    I agree! Also there is the possibility that they are Left Hand Thread. You might want to check with the manufacturer (if possible) to confirm. Also heating and then applying WD-40 will sometimes help loosen frozen bolts.
    David
    Last edited by David Buchhauser; 05-26-2021 at 1:00 AM.

  12. #12
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    I've never had luck drilling off only the head. Drilling out the entire body works quite well, but your drill is never quite perfectly centered. Start small and creep up in size. Once one side of the hole nears/reaches the screw's threads, the remainder (the thicker side) almost always comes apart in little spirals or crescents that come out with the drill swarf. Any remaining pieces can be easily cleaned out with an ice pick or a thread tap with no effort. Damage to the hole's threads will be minimal to non-existent.

    Worse case: drill and tap for a larger screw; however, that is rarely necessary.

    A hard screw in a soft material (e.g., steel screw in aluminum) is hard to keep a drill from wandering.

  13. #13
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    When dealing with dissimilar metals, galling may cause lockup. I like "Liquid Wrench" as a penetrating oil. I would recommend turning the works sideways, so the platter faces up.

    Before loosening, tighten the bolt slightly.

    This might be enough to free the threads.

    (There should be some sort of access hole for a screwdriver or drift pin to hold the arbor stationary, while handling these screws.)

  14. #14
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    The mig works very well on cast iron, I'd be very cautious on aluminum but it'd probably work there to. Risk is making too much heat and damaging the aluminum. Personally I'd consider asking a machinist first, they have some tricks that might work, then go to the welder if not.

  15. #15
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    Step one is use a dental pick to clean the socket of all crud so the hex wrench sits all the way in. They may have used loctite so heat, 500F, will loosen the bond. Then try the manual impact driver. If you drill it out start small then switch to a left handed drill.
    Just for fun look at a tap burner, similar to edm.
    Bill D

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