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Thread: Required torque for M4 and M5 stainless steel bolts into aluminum part

  1. #1
    Associate Engineer
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    Required torque for M4 and M5 stainless steel bolts into aluminum part

    Hello all,

    I am new to this forum, and would like to ask a question.
    I will need to use M4 and M5 stainless steel bolts on 6061 aluminum part.
    Do you know what is requred max torque for this type of application?
    Should I use helicoil inserts as well?
    Thanks for the answers.

  2. #2
    Technical Fellow
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    Are you aware of the galvanic corrosion issues with stainless and aluminum? Do some research on that first.

    What grade of stainless?

    Check this
    http://www.engineersedge.com/calcula...shear-aisc.htm

    It sounds like you may not have done any research on this issue yet. We love to help, but hate doing everything for you.

  3. #3
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    Very good point PinkertonD, also I forgot to mention that I will hard anodize aluminum part with black coating, so it should protect the parts from galvanic corrosion.

  4. #4
    Administrator Kelly Bramble's Avatar
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    Should I use helicoil inserts as well?
    If the bolts are going to experience fatigue or repeated removal and installation threaded inserts are a must. A trick folks do to manage the corrosion issues with Stainless against Aluminum in a corrosive environment is to coat the thread and threaded insert with a sealing paint (zinc chromate) or equivalent to keep out the oxygen.

    In general, it is not a good ideal to anodize threaded features. One can, however the threaded features would need special manufacturing processing.

  5. #5
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    Kelly+1

    Threads in aluminum will get eaten away during the cleaning process for anodizing. They use Caustic solutions which will change the thread form quite significantly. Inserts may be your best option, but only you can decide that based on the environment the materials are working in.

  6. #6
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    This guy's advice sounds quite right. The Galvanic corrosion must be a problem in this application.

  7. #7
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    I just learned that I will not have enough space for the helicoil inserts due to tight spacing of my parts.
    I should probably go with some solution over the threads to prevent corrosion.
    Any ideas on that .
    Thank you all.

  8. #8
    Administrator Kelly Bramble's Avatar
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    Ok, so what is the environment? Will your end item live in a salt, desert, room or where?

    I designed spacecraft hardware for years and we threaded Stainless Steel into Aluminum (6061) all the time. However, the hardware was stored in a humidity controlled room before going into space (vacuum).

    Also, what specifically in the loading on the fasteners and thread? static, dynamic or what?

  9. #9
    Associate Engineer
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    The bolts are holding top SS cover to aluminum housing which is chamber.
    The media is hydrogen gas in one case, and in other one it is air/water mixture.
    This is static load for now, but it might turn into vibration as well.
    Thanks.

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