Old back boxes

[Aragorn84]

I've been replacing some switches in the house with standard plastic ones and ditching the horrible metal dimmers the previous owner had fitted.

The back boxes installed are presumably dating back to when the house was built in the 1950's, and appear to be cast iron. Its been rewired at some point, probably late 70's early 80's given the CU and whatnot. All the cabling is PVC and switches and sockets are of a 70/80's style. However it seems that the back boxes have a narrower bolt pitch than modern switch plates have. I presume the sockets are the same, but i've not got round to digging those out yet.

They all have weird steel adaptor things fitted, which are like a flat strip of metal, screwed into the original two holes, and provide a pair of holes at the correct position for the current style faceplaces. In theory this sounds fine, however the new PCD is such that the screw holes overlap the edges of the old backboxes. This means that normal lenght faceplate screws bottom out on the edges of the back box, and clearly the hamfisted previous owner hasnt bothered noticing this and mangled the scerws in anyway wrecking the threads. This means quite a few of the switches are now held in by one screw. Not ideal.

I'm sorta resigned to digging these crappy old backboxes out the wall and replacing them with modern ones, but i figured i should ask here if anyone has come across this before and solved it in a non-bodged manner?

 

[RF Lighting]

The adaptory things normally allow both the faceplate screws to go inside the old cast iron box.

Perhaps you have a none standard size box or something? Anyway, you know the best thing to do is fit new proper steel boxes, but in the mean time, you could try removing a bit of the cast box with a grinder where the screws go, and maybe fabricate a new adaptory thingy? I've never seen them on sale as long as I've been in the job!

 

[sparkwright]

Are the cables 'singles'?

If so, it would be likely the box is connected to the conduit which the cable is run in.

If so, you would ideally need to connect the conduit to the new back box, if you end up replacing them.

Is this a council house by any chance?

Would shortening the faceplate screws solve the problem?

Extension screws are available, maybe you can shorten these, fit them to the adapter bracket as far as you can, then screw short faceplate screws INTO these extensions.

If you do end re-using the old adapter brackets, you may need to re-thread the fixing holes, with a simple 3.5 mm threading tap, available from most electrical wholesalers.

 

[PrenticeBoyofDerry]

Picture would be helpful.

 

[Aragorn84]

Cables are not singles, just normal twin and earth. Though they might have been singles when originally installed I guess!

I'll try and get some photos tomorrow night.

The brackets sit flush with the wall as they're wider than the original box, so the extension screws wouldn't work I don't think.

Retapping and short screws might work I guess.

Yes its an ex-council house.

 

[sparkwright]

If there is conduit, you would need to check the box can be removed without disturbing the conduit.

I seem to recall there were some conduit system where the box was screwed directly onto the end of threaded conduit, during erection. If there's no locknut to remove, it could be a swine removing the box without disturbing the conduit. If you see what I mean.

 

[DaftPunk]

A couple of sharp blows with a cold chisel usually gets the box off the conduit with minimal damage to the surrounding plaster work

 

[333rocky333]

http://www.tlc-direct.co.uk/Products/MK3840.html

As Rf says there not that easy to get hold off nowadays