I’m replacing a botched 3 gang switch box (formerly consisted of two incompatible boxes together, cover plate did not fit right).

I have clamps on all my cables and am ready to put them through the box knockouts and into the wall, but due to many of the cables being of the very old, brittle, cloth covered type, I am afraid to wiggle things around too much. Any tips for this situation? I have tried starting with different cables first but it is very hard to get more than two at a time through, and the cables are so inflexible that I am afraid it will be really hard to get it into the wall.

I am trying to get the two yellow NM cables in a single clamp to come into the box from the bottom, and the rest are coming into the top and the rear of the box. The box I am using is 3x 2.5” deep gangable metal old work box. Knockout size 3/8”. Wall is lathe and plaster.

Cables in wall cavity

  • What type of cableclamp are you using? Dec 12, 2020 at 22:59
  • @ThreePhaseEel bag says ‘NM Cable Connector, 3/8” trade size, 1/2” knockout’. They are the kind tightened around cables with two screws and then have a nut that goes on inside the box to secure to the box
    – Ivan G.
    Dec 12, 2020 at 23:06
  • And you'll have three switches in there?
    – JACK
    Dec 12, 2020 at 23:42
  • @JACK yeah. If you are heading in the direction I think about box fill, there are a total of three /2 NM cables, and then 7 single conductor fabric cables. Haven’t done calculations myself yet, I have been away from my computer
    – Ivan G.
    Dec 12, 2020 at 23:48
  • The only thing that makes this old work is it's actual age. Drywall is the enemy, even if it's l&p. Electrical Box, Masonry, 67.3 cu in, 3 Gang, Amazon. - Not that you have enough wire, but usually I do right angle fittings and come in from the rear KOs; that's the only way they like to 'slip' in.
    – Mazura
    Dec 13, 2020 at 0:23

1 Answer 1


I'd use a different style of clamp for this job

Given that you're in an old-work situation and dealing with fragile cables, I'd use a style of clamp such as a Raco Insider or Arlington White Button that's designed to be installed from inside the box instead of from the outside of the box the way a traditional (two screw) NM clamp is.

  • I was getting ready to go get some new clamps and try this, but unfortunately I don’t think it will actually help this situation. The metal clamps aren’t getting in the way, it’s just too hard to get all the cables through the holes and push the box in, so I’m afraid I would have the same problem with the other clamps
    – Ivan G.
    Dec 13, 2020 at 19:48

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