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Thread: Removing mild steel keel bolts from a cast iron keel

  1. #1
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    Default Removing mild steel keel bolts from a cast iron keel

    When the ballast keel was removed from Laurent Giles "Audacity" drop keel boat due to the drop keel being seized inside the slot, I fount 5 of the ten bolts has sheered level with the top of the ballast. The others tapped through with varying degrees of effort required but I need the remainder removed before replacing all bolts. I have tried a few times with soaking with various penetration preparations followed by hammering with a drift and large hammer, but no budge.

    I was thinking along the lines of heating but its a big mass of metal to heat (I'll attach pic in a minute)

    Any other suggestion short of drilling would be appreciated - they appear to be at a slight offset to vertical.......

    https://www.dropbox.com/sh/n067xmwku...AdsI1HCEa?dl=0

  2. #2
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    Default Re: Removing mild steel keel bolts from a cast iron keel

    I am assuming the bolts pass through the ballast keel with plugs over the bottom heads? If so, you might try a longer soak from the top with better penetrating oil and then tapping them out again with the drift. An air hammer can be a big assist for this as it often will rattle the bond loose. If some do not pass through, then the oil will help in conjunction with an easy out to unscrew them if there is not enough shank left to ge a wrench on to unscrew them. There is also the choice of having a pro do it with spark erosion. Frozen bolts in engine blocks often are removed that way.
    Jay
    Last edited by Jay Greer; 06-16-2017 at 11:59 AM.

  3. #3
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    Default Re: Removing mild steel keel bolts from a cast iron keel

    Quote Originally Posted by Jay Greer View Post
    I am assuming the bolts pass through the ballast keel with plugs over the bottom heads? If so, you might try a longer soak from the top with better penetrating oil and then tapping them out again with the drift. An air hammer can be a big assist for this as it often will rattle the bond loose. If some do not pass through, then the oil will help in conjunction with an easy out to unscrew them if there is not enough shank left to ge a wrench on to unscrew them. There is also the choice of having a pro do it with spark erosion. Frozen bolts in engine blocks often are removed that way.
    Jay
    Thanks, Jay! I learn something new in here all the time. I hadn't heard of spark erosion machining before. There's a good explanation of it in Wikipedia.

  4. #4
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    Default Re: Removing mild steel keel bolts from a cast iron keel

    EDM
    Electrical Discharge Maching, usually reserved for hardened or "unmachinable" materials.

    The object has to be immersed in a fluid. Large objects = Large $$$

    I would think seriously about drilling it. Drilling can be done in situ or in the boat yard. A magnetic drill press is quite a tool, and would get you set up and accurately piloted enough to continue drilling through by hand.
    Hammering on it in any fashion is liable (almost guaranteed) to expand the part diametrically, eventually making it almost impossible to remove without drilling.
    edit to add; If you have some acces to the end of the bolt you may be able to weld an adapter to use a hydraulic puller. Basically this can be a bottle jack or two used to apply force to the bolt away from the keel itself. If you can pull hard enough, the part will become diametrically smaller.
    Last edited by Canoeyawl; 06-16-2017 at 12:33 PM.

  5. #5
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    Default Re: Removing mild steel keel bolts from a cast iron keel

    I would suggest NOT getting drill bits from the big box stores. make the effort to get industrial type drills and a slow speed drill, Kroil is a great if if you find it!
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...58#post3996158

  6. #6
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    Default Re: Removing mild steel keel bolts from a cast iron keel

    Ive had great success by welding a nut onto the remains of the bolt shaft, as long as the broken shank isn't really deep inside the body holding it. Basically, set a washer down around the broken shank, and tack a good sized nut to the washer.
    Then weld the nut to the broken shank and fill the inside of the nut thread with molten filler rod. Do it hot and fast and fill the nut bore full. Let cool until COLD. Then try breaking loose by using firm raps with a hammer and back and forth raps with an impact tool.
    What is the diameter of the bolt shaft?

  7. #7
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    Default Re: Removing mild steel keel bolts from a cast iron keel

    Yep, EDM + keel bolts =$$$$. We have three EDM machines where I work. You would have to find a pretty specialized machine shop that would have an EDM machine big enough. Our machines hand 'loaf of bread' kind of size and smaller. EDM is for when you need +/- .0005", or highly detailed work.

  8. #8
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    Default Re: Removing mild steel keel bolts from a cast iron keel

    I suspect that you will have to drill them out as canoeyawl suggests (#4).

    You could investigate a Thermal Lance – I have had some success with those in the past, with a similar situation. Depends to some extent on how long the corroded-in bolts are. Thermal Lance technology is not incredibly expensive and can be very effective.

    But drilling might be cheaper and not so very difficult. The mild steel will normally drill out in preference to the cast iron, once it gets a start. You do want good drill bits however. If you are going for drilling, I think I would go for a full size drill (i.e. bolt diameter) in one hit as this will more likely stay true to the hole in the keel.

    Cheers -- George
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  9. #9
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    Default Re: Removing mild steel keel bolts from a cast iron keel

    ?? Do you have any option to drill and locate "new" bolts?

    If so you may be able to avoid the extraction of most of the existing bolts altogether. Just thinking out loud.

  10. #10
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    Default Re: Removing mild steel keel bolts from a cast iron keel

    Here is a more out of the box idea. You could also try vibrating the stubborn steel keelboats. Sometimes variations in vibrations in a rod will break oxidation bonds through harmonics. A combination with Penetration oil could work. A tapping ballpin hammer on a double nut or a double nut with a ossalating applied sander can loosen a part free.
    There is nothing you can do with an ape/human hybrid. They'll rip your arm off.

  11. #11
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    Default Re: Removing mild steel keel bolts from a cast iron keel

    There's a difference between wire EDM full-on precision machining and using EDM spark erosion to clear a bolt hole. Shop for 'tap disintegration' or call up an automotive machine shop. It can be a cost-effective solution. (Tap disintegration is used to clear a broken-off tap in a hole. Taps are really hard, and highly resistant to being drilled out.)

    If you can get some heat into it, melting candle wax on it will work, according to reports. It works down in the threads via capillary action. Kroil will sometimes do the job, or ATF mixed with acetone. PB Blaster.

    Harbor Freight (obligatory boating reference) has left-handed drill bits. Use a small grinder to 'level the playing field' then center-punch it, and carefully/slowly start drilling out the bolt with your drill in reverse (because the drill bit is left-twist) and with as much pressure as you can muster. As you're making a hole, heat, vibration, and torque will all pay a visit, and if you've lived a clean life, it may come out. If it doesn't, your bolt remover will go right in the hole. Get the square kind, not the twisted-up kind. The square kind doesn't expand the bolt as much when you're backing out, and the four straight teeth get a good grip, and stay gripped when you tap (pound) it in more as needed.

    All great things to try. Sadly, no guarantees, though.

    Good luck!
    Chip

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    Default Re: Removing mild steel keel bolts from a cast iron keel









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  13. #13
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    Default Re: Removing mild steel keel bolts from a cast iron keel

    If you need to drill them out it's possible to rent a magnetic based drill press that will allow you to drill accurately .
    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

  14. #14
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    Default Re: Removing mild steel keel bolts from a cast iron keel

    So how much does that weigh? Is it about 6 feet long?
    I would sorta not worry about leaving a clean hole, because my "eyeball engineering" says they should be bigger bolts. That comes with the opportunity to drill new holes and tap them. Bigger bolts mean bigger thread depth, which should help. Consider anti-seize, if you can lock the heads in place so they remain tight no matter what.

    Chip

  15. #15
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    Default Re: Removing mild steel keel bolts from a cast iron keel

    Thanks for all the pointers. Bolts are 1/2 inch straight through with a square head. Can't relocate, but as inner ribs are short infill pieces that support floor, could theoretically move both. First try will be hydraulic pull on square head end. Plenty weld surface. If not magnetic drill with self piloting drill bit...ill report progress...

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