I can't disconnect this old metal box from the metallic conduit that is behind it. From the pics you can see I was able to remove the old rusted fasteners and replace them with new ones.

However I soaked that thread/nut with WD-40, grabbed the conduit connector that is behind with pliers and tried to turn it, that didn't do a thing.

How do I remove this box?

Box Thread

  • 4
    what happens when you remove the two Philips screws
    – Traveler
    Feb 29 at 5:45
  • 2
    If you are trying to replace the box, why did you replace the screws that hold it to the wall? If you want to replace the conduit only , you need axcess behind the box. Grab the conduit and turn counter clockwise. It would help us here if you stated your final intentions.
    – RMDman
    Feb 29 at 13:03
  • Can you tell if the conduit is EMT or something heavier? I'm guessing that is threaded into the back of the box which was manufactured with a tapped hole. It also looks like a sealant or adhesive was applied to the threads. In that case there are a couple of choices. If you just want to be rid of the box you could cut off the conduit behind the box and pull the remaining stub through. A hole saw without the pilot bit could be used to cut out the center of the back wall of the box. At that point you could remove the box.
    – HABO
    Feb 29 at 14:11
  • 1
    I'm guessing that @Traveler is right on the money. It looks like those two Phillips head screws are holding the box to the wall. Remove them and you'll have an infinitely better chance of getting the box unscrewed from whatever kind of pipe that is behind it.
    – FreeMan
    Feb 29 at 15:54
  • 1
    Thanks and maybe I wasn't clear enough but I did initially remove the old and rusted Philips screws. When removed, the box can rotate freely (360°) but so does the conduit behind with it. I took the pic when I had already given up and added new screws, I was at that point in the process of putting everything back together and had almost forgotten to take a pic. I would like to avoid cutting the conduit behind as I'm not too sure how to replace the threaded connector, it is a steel conduit (I'm in Chicago)
    – Goxoa
    Mar 1 at 3:31

5 Answers 5


There are penetrating oils better than wd40. Try some. I'm reluctant to recommend any because that always takes over the conversation. Search this forum for opinions.

If you have access to the back of the box and can disconnect the connector from the conduit, you could just replace the box or saw the connector off from the back.

You could use a Dremel to cut the nut then pry it off.

  • 6
    There are penetrating oils better than wd40...not hard, when WD40 isn't one to begin with.
    – Huesmann
    Feb 29 at 17:01
  • 2
    @huesmann and for everything else it does there something else that does it better. But being able to do everything makes it useful for the average joe...
    – Questor
    Feb 29 at 21:49
  • Thanks and feel free to suggest one I won't argue with you. WD-40 is all I had but I will definitely look for something stronger.
    – Goxoa
    Mar 1 at 3:26
  • 2
    People seem to like Liquid Wrench. I use Silicroil, mainly because that's what I have.
    – jay613
    Mar 1 at 4:59

grabbed the conduit connector that is behind with pliers

Threaded conduit is basically high-quality (smoother inside) pipe. Given you have an old cast aluminum box with (probably) galvanized steel conduit screwed into it, "pliers" is highly unlikely to work. Try a pipe wrench, preferably one with about a 2 foot handle. That connection is welded together with years of corrosion.


That doesn't look like a ring: that looks like an integral part of the box with threaded conduit screwed directly into it.

Get yourself some penetrating oil, and work out how to hold both the box and round conduit.

Oh, and write out 100 times "WD40 is Water Displacer (formula 40), not penetrating oil".

  • 1
    It's a penetrant. Whether it's "oil" is irrelevant. I agree that there are better penetrants to be had, but if that's what's on hand it'll probably work fine. Peanut butter also works as a "baby head lubricant" even though it's not labeled as such.
    – isherwood
    Feb 29 at 14:24
  • I'm not sure, @isherwood, exactly what "baby head lubricant" is used for and I'm terrified of doing a web search for peanut butter used in that context! O_o
    – FreeMan
    Feb 29 at 15:53
  • 2
    Stairs built before the 4 inch ball rule, or in violation of it. They get their heads through, and then can't get them back out. Thus, the 4-inch ball rule. Shortening or butter will also serve.
    – Ecnerwal
    Feb 29 at 15:57

I would likely use a hammer, cold chisel, and cat's paw to just destroy the box. If I was feeling a little more delicate first I might with an oscillating saw score the back of the box to 3 or 4 pie shaped wedges then cut the sides down to meet the scoring.


Try removing these two screws:

enter image description here

Then see if you can get the box off the conduit. They very much seem to be holding the box tight against the wall and I don't think any amount of rust remover/penetrating fluid/gigantic pipe wrenches will work until they're removed.

  • Thanks but as mentioned above I had removed those screws already and replaced them with new. When the screws are off the box turns with the conduit but can't detach it. I actually took the pic when I had given up for the day and was in the process of putting everything back the way it is, as I need to look for a solution.
    – Goxoa
    Mar 1 at 3:17

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