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Thread: Gaggia Classic: snapped allen bolt head on OPV

  1. #1
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    Gaggia Classic: snapped allen bolt head on OPV

    So after battling an intermittent blockage which is now more so permanent, I decided to dismantle the machine with aim of complete refurb - this is a 14 year old machine that I picked up two years ago, it has had a some minor repairs and TLC since I took ownership but otherwise has 14 years worth of crud to clean up.

    Long story short, I removed the boiler and attempted to remove the OPV from the boiler however, as the Allen bolts are very much on the rusted side, I have managed to snap the head off an Allen bolt (see picture).

    Can I drill out the thread without too much concern, if so what drill bit would be recommended? Open to all suggestions here.

    E68AC33E-4952-40B5-B331-8FC6AE7F268A.jpg

    Many thanks!

  2. #2
    Mal Dimal's Avatar
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    G'day mate...

    See if you can break the other bolt off, or cut it off and then set about loosening the OPV from the boiler via jiggling it around, light tapping with a wooden mallet, etc...
    Once the OPV is removed, you will find it a lot easier to remove the remainder of the bolts, either by using vice-grips, an ezy-out, drilling out and retapping, etc. Lots of options...

    Mal.
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  3. #3
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    Thanks for quick response Mal!

    Didnt actually expect to be offered a solution of breaking the remaining bolt and then prying the OPV from the boiler but it makes sense.

    I have the group head and bottom of boiler soaking in descale at the moment as thought that will get some of the scale/rust from the bolts and allow more movement.

    Thanks again, I will update this thread one I have another crack tomorrow.
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  4. #4
    Senior Member Lyrebird's Avatar
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    Oxalic acid (available from paint places as "rust and stain cleaner") will be more effective than standard descale: oxalic is one of the few things that will actually dissolve rust. One of the others, surprisingly, is molasses: the usual recommendation for old bike parts is to soak the whole thing in a 10% solution of molasses in water, but this can take several days to work its magic.


    Another trick is that the thermal expansion coefficient of brass is higher than that of steel, so if you heat the boiler with a torch the bolt should be easier to remove.
    Last edited by Lyrebird; 2 Weeks Ago at 10:39 PM.
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  5. #5
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    Thanks Lyrebird.

    The boiler on the Gaggia Classic is aluminium so I’m not sure heating the bolt will be as effective? Oxalic acid sounds promising, I will read up on whether this is okay with the aluminium else it looks like cutting off the remaining head and then prying off the OPV will be the resolution.

    Appreciate all the input thus far!

  6. #6
    Senior Member Lyrebird's Avatar
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    I meant but didn't state that you should follow Mal's suggestion before mine: I am suggesting ways of making the bolt extraction easier after you have the OPV safely off.

    That being said: yes the Tce of aluminium is higher than brass and thus much higher than steel, the downside is that aluminium boilers are often lined with teflon or similar so they won't take the heat.

    On the other hand it is supremely easy to get a stuck steel fastener out of aluminium by dissolving the fastener but not the aluminium in acid. I've had to do this several times after ham fistedly snapping off a tap in a deep hole in ally. Hydrochloric is fastest but you'll need to be very careful.
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  7. #7
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    Well, good news, I managed to remove the remaining fasteners. I should be able to extract the snapped one quite easily. Now to dismantle the rest of the boiler, which I’m thinking is going to be pretty ugly internally - good thing I love a challenge!

    3A0506B4-1440-45A4-9157-3A89B1955EA0.jpg
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  8. #8
    Senior Member CafeLotta's Avatar
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    Penetrene is always a good thing to have on hand to use on really rusted screws before attempting removal. Found it to work better than WD40 or CRC on badly rusted fasteners. On really rusted items you need to give it some time to do its thing.

    Penetrene – Protectant, Lubricant and Rust Penetrator | Quick Smart Products
    Last edited by CafeLotta; 2 Weeks Ago at 03:45 PM.
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  9. #9
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    Quote Originally Posted by CafeLotta View Post
    Penetrene is always a good thing to have on hand to use on really rusted screws before attempting removal. Found it to work better than WD40 or CRC on badly rusted fasteners. On really rusted items you need to give it some time to do its thing.

    Penetrene – Protectant, Lubricant and Rust Penetrator | Quick Smart Products
    +1. It even works on a lot of "beyond all apparent hope" cases (even underwater). Nothing I have used comes close to its ability to separate the inseparable and remove corrosion as a welcome side effect. Worst case I know of took 3 weeks of daily application (a 1934 Mercedes engine, seized in 1938, freed after three weeks of daily penetrene in 1999 - it then spun like a watch and didn't need the crank or three of the pistons done).
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  10. #10
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    TBH, the aluminium upper boiler is shot. That much corrosion is likely unsalvagable as I can see the pitting on the boiler face externally. I don't think you can resurface the aluminium to still seal suitably.
    You may be able to salvage the boiler base, which is brass, but it will have lost its chrome internally.

    To remove the upper half, you will either need to use a lot of time and patience with penetrating oil/chemical/whatever. OR...In cases that have looked better than this, I often intentionally remove the bolt heads using a Dremel cutting tool, then gently tap a Stanley knife blade between the halves to seperate. The boiler halves are glued together by the corrosion interlocking in the threads of the bolts and the holes in the aluminium upper boiler. The longer bolt remnants are then easy to remove from the brass lower boiler as they won't have the corrosion and can be gripped easily with multigrips to unscrew. Hopefully they are not corroded beyond even this!
    PM me if you need advice used to refurb these machines when I lived in the UK.
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  11. #11
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    Thanks timmyjj21, your words have effectively summarised my thoughts - this boiler is likely well beyond any satisfactory repair, not to mention the time cost spent thus far attempting to repair in comparison to cost of new parts is now in the negative (I value my time).

    It has been an excellent experience with respect to truly understanding the ins and outs of the Gaggia Classic.

    I’m now going make the most out of having the machine apart and commence an Arduino PID project to complement the new boiler and group head.
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  12. #12
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    For those following along and/or have concern about my lack of caffeine consumption...

    It has been nice using the V60 exclusively for the last week but I can happily say that this morning the Classic (who’s actual build date is 2002, making it 16 years old rather than 14) pulled its first few shots after having a new boiler and group head installed. The old timer is tighter than ever, and much much cleaner.

    I’m not sure if it is lack of espresso for a week but the Frankenstein blend (unknown quantities of Yirg, Indian EH, and Volcan Galeras Especial) that I pulled this morning was incredible. Even with my man flu I was getting notes and depth I hadn’t experienced before with that blend!

    I didn’t end up going the PID option, that’s a task for another month.
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