What is this strange back box?

Found on a job today.

Unlike a normal back box, it does not have lugs at the edges, but 2 solid posts, closer together, with tapped hole more like 2BA size rather than 4BA / M3.5



Which explains why they have all been "modified" to fit a modern light switch



1950's or 60's house, probably original boxes made by GEC

I have never seen these before. Looks like I have the fun of chopping them all out and fitting new boxes.

I'd make a guess that a circular dolly switch ,  possibly porcelain & brass ,  fixed with the two screws  and the front plate held in place with a small lock bezel  .

I did wonder if I could try a flat plate screwless switch, and re drill the mounting holes, to save chopping out the boxes.

I'd agree with Deke...

Old conduit wired switch where the main gubbins of the switch fixes inside the box, with separate cover over the front...

Similar principle to this outdoor conduit switch... 



But the cover for this one had a weatherproof seal and a lever arrangement that operated the toggle switch..



Guinness

ProDave said:

I did wonder if I could try a flat plate screwless switch, and re drill the mounting holes, to save chopping out the boxes.

Click to expand...

Multi-tool around the outer edge of the box to break any bond with the adjoining plaster, should make is quite easy to ease it out...

Used that method numerous times easing single-gang boxes out of the wall to convert to double, while minimising any damage to the plaster....

opcorn  

Thanks for the photos.

So whoever rewired this house, probably in about the 70's just fitted the wooden inserts and left the job of replacing the back boxes to the next spark (me)

To compound the back box swap, the drop is in steel conduit so I need enough clearance to drop the box down to clear the conduit end.

ProDave said:

I did wonder if I could try a flat plate screwless switch, and re drill the mounting holes, to save chopping out the boxes.

Click to expand...

drill and tap the back of the back box.

OR you could go,out on a limb and use the correct bracket for the job!

leave the box, leave the conduit, simples

https://www.sparksdirect.co.uk/MK-Box-Fixing-Bracket-with-Earth-Terminal-Fixing-Flange-Old-to-1G#.XRu-VdHTWhA

I always keep,a,few in the van just in case....also,handy if a box lug shears off

kerching said:

OR you could go,out on a limb and use the correct bracket for the job!

leave the box, leave the conduit, simples

https://www.sparksdirect.co.uk/MK-Box-Fixing-Bracket-with-Earth-Terminal-Fixing-Flange-Old-to-1G#.XRu-VdHTWhA

I always keep,a,few in the van just in case....also,handy if a box lug shears off

Click to expand...

Thanks. My job has just got a lot easier. I never knew those existed.

ProDave said:

Thanks. My job has just got a lot easier. I never knew those existed.

Click to expand...

You're welcome!

discovered them about 35 years ago when rewiriing an old mansion. On occasions you may have to nip of a tiny bit from the wings . They are even slotted in the correct place....Better still if you have the old retaining screws BUT Orbix or similar will do

it was same job as we discovered Unibond Decorative filler ( all,walls were sort of textured/Artex plaster and couldn't get a good finish around socket/switch plates. Saw joiner using it when he scribed a melamine wardrobe frame in. Now you can get decorators caulk everywhere.this stuff came in a toothpaste type tube