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Thread: Flange screws

  1. #1

    Join Date
    Dec 2001
    Location
    San Joaquin Valley, California
    Posts
    9,599

    Flange screws

    I'm concerned about using different metals together. I've seen Fiats self destruct because iron waterpumps were installed on aluminium engine blocks and I've heard of the historically notorious freezing of the (iron cannon)balls off the(brass)monkey which (you guessed it) brings us to the subject of lens flanges and the screws used to attach them to the lens board. My SOP is to use brass screws when mounting brass flanges and steel screws when mounting steel flanges but I just received an aluminium flange that fits a compound shutter, so the question is(since I can't find any aluminium wood screws) is whats best to use on aluminium, steel or brass? Or, am I overly concerned about the whole thing and it really dosen't matter as long as the screws are strong enough to keep the lens from falling off??

    Thanks!
    "I would feel more optimistic about a bright future for man if he spent less time proving that he can outwit Nature and more time tasting her sweetness and respecting her seniority"---EB White

  2. #2

    Flange screws

    I think you are being overly concerned about disimilar metals. The serious problems occur when the two metals are in contact with water because an electrolytic reaction ensues. If you are still worried, use stainless steel screws.

  3. #3
    wfwhitaker
    Guest

    Flange screws

    Overly concerned.

    The Fiats would have self-destructed anyway. They're Fiats.

  4. #4

    Join Date
    Dec 2000
    Location
    Tonopah, Nevada, USA
    Posts
    6,334

    Flange screws

    It doesn't matter because the brass lens barrel is going to freeze into the aluminum flange and you'll have to pry it out of the lensboard with a claw hammer. Use soft screws so the heads will pop off.

  5. #5

    Join Date
    Dec 2001
    Location
    NJ
    Posts
    8,469

    Flange screws

    John, I've never used antiseize compound on a camera because I'm not sure what will vaporize out of it and condense where I don't want it, but the research needs to be done. Here's your chance to serve society, go to it!

    Cheers,

    Dan

  6. #6

    Flange screws

    I doubt if there is any problem as the material used would not be pure, but an alloy which is treated to prevent chemical or other deterioration when used in conjnction with other metals. Rest assured.

  7. #7

    Join Date
    Jun 2001
    Location
    obx,nc
    Posts
    173

    Flange screws

    John, From my sailboat experience... stainless and aluminum are one of the worst combinations. Moisture in the air is enough to start the reaction. Try Bronze if it's available. A search for fasteners on the web might lead you to a retailer that carries aluminum screws or bolts. (#6 or #8 machine screws should be fine). Maybe S K Grimes has some in stock.

  8. #8

    Join Date
    Sep 2003
    Location
    New Jersey, USA
    Posts
    267

    Flange screws

    Another boater's vote against mixing stainless and aluminum. In a saltwater environment (some spray) I've seen the aluminum corrode in THREE WEEKS.

    If you want aluminum screws, try use-enco.com it's Enco machine supply, and they have no minimum quantity. If you're really worried, used plastic fasteners

  9. #9

    Flange screws

    I totally agree with the above advice, NEVER mix stainless steel, 365 marine grade, or otherwise, with aluminium in any form. If possible use mono metal which is a form of protected hardened aluminium. You will then be able to use your camera under the red sea! (EX.RN sea diver).

  10. #10

    Flange screws



    John isn't making a car water pump nor a sail boat, nor was he asking about sea diving. I don't expect that the metals he uses will be in constant contact with water, and I don't expect corrison to be a problem for his flange and screws.
    If salt water got splashed on his lens, he probably should take it apart as much as possible and wipe it off with fresh water.





    See http://www.corrosion-doctors.org/Aircraft/galvdefi.htm for information on "Galvanic corrision". If someone still wants to be careful, consult a table of a "Galvanic Series", such as http://www.corrosion-doctors.org/Air...eri-compat.htm.
    If you still want to consider this corrison issue, the table lists plain low allow steel as being galvanically close to various aluminum alloys and better than the stainless steel I suggested. However, probably most hardware store screws are zinc plated, which makes them more disimilar to aluminum.





    I can't think of any old lens that I've looked that the showed extra corrision around the flange mounting screws. Any corrison is usually over the entire surface and isn't from the contact of dissimilar metals. This shows the results of decades of use and storage -- nor do I think that the old timers were using screws of exotic alloys.





    I've never heard of "mono metal" and haven't found anything on the web or in a reference book that I have. Was "Monel metal" meant? However, Monel metal is a nickel alloy that is galvanically farther from aluminum than stainless steel.


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