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Removing old knob and tube porcelain fixtures « Well that was… an idea
02 Mar 2010

Removing old knob and tube porcelain fixtures


This isn’t a post about replacing old wiring with new three strand Romex.  (There will be posts on that, don’t you worry your pretty little heads.)  No, this is a post about a seemingly small but very poorly documented task related to such replacements – removing the knob and tube porcelain fixtures themselves.  Note: The following pictures are of completely dead, orphaned wiring segments – they have not been attached to the electrical panel for decades.  Never muck with live wiring, especially live knob and tube.

 
In this image you’ll see both knobs – the thicker cylinders jutting out from the beam – and tubes – the thin, hollow cylinders, one of which is strung horizontally for some reason, one of which is inserted into the beam next to the first knob.  Tubes are pretty easy to remove -the hole drilled for them years ago is snug but usually a bit bigger than they are.  All you should have to do is slide it out – at worst, a quick yank with pliers will do you.
The knobs seem somewhat more daunting.  They don’t unscrew or come apart on their own.  Each should consist of two porcelain segments, one thicker than the other, and a heavy nail running through them into the beam:

The nail likely extends an inch or less into the beam:

Removing knobs, then, is a fairly straightforward matter of wedging a hammer between the beam and the porcelain, and levering the nail out using the entire fixture. This next picture doesn’t show how far I actually inserted the hammer – quite close to the nail:

I was a little unsure at the start of this project for fear of shattering porcelain everywhere. It doesn’t seem to be an issue – the porcelain will likely chip and flake, especially as you’re first working the hammer in behind the knob…

… but it’s stronger than you might think.  A gentle-but-firm approach had a half-dozen knobs out in less than ten minutes, and even an overzealous pull on one resulting in it flying from the beam and clattering to the floor didn’t cause any of them to break. 

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