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tank hatch terminology

Discussion in 'Technical Discussion' started by Capt Ralph, Apr 5, 2015.

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  1. Capt Ralph, Apr 5, 2015
    #1
    Capt Ralph

    Capt Ralph Senior Member

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    I opened up an inspection hatch on a fiberglass water tank by removing many machine bolts along its perimeter.
    Inside the opening is an alloy bar with threaded inserts thats acts as the nuts, retainer & backing plate to the cover hatch and thru bolt arrangement. A few of these threaded inserts are stripped or damaged.
    Seems like a simple enough piece of hardware.

    I'm having a brain fart tonight but I can not think of what to call this item or find replacement bars on the web.
    It's late and I'm tired but nothing comes to mind on what to even call it.

    Any ideas out there?

    Attached Files:

    Last edited by a moderator: Apr 5, 2015
  2. Capt Bill11, Apr 5, 2015
    #2
    Capt Bill11

    Capt Bill11 Senior Member

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  3. Donzi 54, Apr 5, 2015
    #3
    Donzi 54

    Donzi 54 Member

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    Google "thread inserts" there is many different styles
  4. Capt Ralph, Apr 5, 2015
    #4
    Capt Ralph

    Capt Ralph Senior Member

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    I'm not wanting to repair what I have with helicoils. I want to replace the attachment bars.
    I have seen ads and articles on them long ago. I'll have to dig up some industrial catalogs .
  5. Capt J, Apr 5, 2015
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    Capt J

    Capt J Senior Member

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    The threaded part is sometimes called thread-certs. Not sure what the backing plate with them in it are called. You might want to just have a few thread certs welded into what you have. I don't think you can buy the backing plate with them in it anywhere. Might need to have a machine shop make it.
  6. Capt Bill11, Apr 5, 2015
    #6
    Capt Bill11

    Capt Bill11 Senior Member

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    I must be missing something. I don't even see any threaded bars in those pictures. Just what looks like threaded inserts in the fiberglass.
  7. Capt Ralph, Apr 5, 2015
    #7
    Capt Ralph

    Capt Ralph Senior Member

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    Maybe a better description;

    Underside clamping ring.
  8. K1W1, Apr 5, 2015
    #8
    K1W1

    K1W1 Senior Member

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    I tend to agree with CaptJ that what you have theRe was made for the job in the quantity required.

    It should be fairly straight forward to remove them and have a machine/welding shop make you a set or two the same.

    You could also just use thicker Alu bar and drill and tap them yourself but you would not get what looks like those little stand prouds that are flush with the fibreglass surround.

    If its only a few that are stripped it might be a lot simpler and economical to Helicoil them and use plenty of Tef Gel or similar to negate any action between Alu and stainless if this is the fastener material.
  9. captholli, Apr 5, 2015
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    captholli

    captholli Senior Member

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    Looking at the photos this looks to be a fiberglass tank flange arrangement using 1/4-20 flat heads counter sunk flush holding aluminum
    flat bar under the tank opening to form a reinforced flange. The fiberglass has thread certs screwed / glued (5200?) into the glass. It would be my assumption that the thread certs are also tapped into the flat bar for added strength. As far as nomenclature goes? "tank manhole bolt flange"?
    Last edited: Apr 5, 2015
  10. NYCAP123, Apr 5, 2015
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    NYCAP123

    NYCAP123 Senior Member

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    I think CaptJ hit it. It's simply a backing plate. K1W1 also when he said just make up a new one. Any welder or machine shop can make it up out of flat stock. If you search catalogs or walk around a hardware store you may find one similar that's made for some other purpose as well.
  11. bobhorn, Apr 5, 2015
    #11
    bobhorn

    bobhorn Member

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    Built the same thing for as fuel tank hatch many years ago. The AL bars are threaded for the cover bolts. The bars are held in place using a couple of flat head screws while the cover is off.

    Bob
  12. K1W1, Apr 5, 2015
    #12
    K1W1

    K1W1 Senior Member

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    It sure looks in the photos like there is Alu that sticks up right to the level of the fibreglass. This is why I suggested using a thicker flat bar to allow for some thread depth.
  13. bobhorn, Apr 5, 2015
    #13
    bobhorn

    bobhorn Member

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    The first picture clearly shows the Phillips flat head screw that is holding the backing plate in place. The threaded inserts look like some type of captive nut. I used those to keep from having to tap the aluminum and possibly stripping the aluminum threads. Look at McMaster-Carr for captive nuts.

    Bob
  14. K1W1, Apr 5, 2015
    #14
    K1W1

    K1W1 Senior Member

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