In this video I going to rethread an electrical back box. This job can be done
very quickly and in most cases you don't even need to remove the switch or the
socket. However it is important that you isolate the electric and it's also a
good idea to have a look behind the switch or the socket before you attempt this, just
in case there's a wire behind or the screw is. In this example I need to
remove the switch because I'm fitting a new one and this is at the top of a set
of stairs. I'm now at the consumer unit I'm going to find the circuit breaker for
the upstairs lights, switch that off and then I'm going to fit the lock off device.
I'm just going to lock that off. Before we touch any of the terminals we do need
to ensure that they are dead the best way of testing these is by using a GS 38
approved voltage tester. I'll give you a demonstration of that on another light
switch. Before we touch any of the wires at the back we do need to ensure that
they are completely dead we're going to do that using this GS 38 approved
voltage tester. This one actually has a self-test function so we're going to
press the auto test, you can see that that is working we're then going to check
that the leads are working by measuring the resistance. So I want to touch both
of the probes together and then press the ohms button so you can see that the
leads are working. We will now just check it's working again. So I'm going to
probe between the top and the bottom terminal and the machine is not
illuminating at all which proves that it is isolated correctly. On some back
boxes you do have a earthing terminal if you do have an earthing terminal you
can put that on the earthing terminal and then you can probe the two terminals
to ensure that it is completely dead. We are now going to check that the
tester is still working by pressing the auto test button
and now I'm just going to press the ohms button and touch the probes together and
that shows us that the leads are still working. So it is now safe to continue.
You can see that I can't actually screw the screw into the right hand lug but I
can actually screw it into the left hand lug that means that the right hand lug
is damaged and need re tapping. When it comes to re tapping the hole you can
either use a tap wrench and then an M3.5 tap if you are in the UK or you can buy a
dedicated tool like this one which is specifically made for
re threading socket back boxes. Once you've removed a switch it really is very
easy all you need to do is take the back box threading tool or the tap
push that directly into the hole ensuring that it is straight and turn it
in a clockwise direction. That will then cut a new thread.
It's important when you screw this in that you don't go all the way to the back you don't
actually want to touch the back of the back box.
So I am now going to unscrew that in an anti-clockwise direction.
Once you have you removed the screw like this it's important that you don't try
and use it again incase it strips the lug again so it's always a good idea to get
a brand new screw. In the UK screws for sockets and switches are always
M3.5. So now it's simply a case of rewiring up the light switch putting the
wires back in the terminals where they came from.
We will then push the switch back into position and replace both screws.
Now we've done the work we can unlock the padlock, we can then remove the lock off device,
and I can switch the circuit back on. If you remove the faceplate and you
realize that you've got a dry lining back box in there you can actually
replace the tabs on some of these to do that you need to push them back the
difficult part about this is actually finding the make of it. There are a
couple of manufacturers of these but sometimes it is cheaper just to buy a
new back box can swap over the tabs providing there will fit. There are a couple
of different makes like I've said and some of them are completely different to
others. This one for example is an Appleby and you can actually get these
out and if you pull it down on an angle like so you can actually remove it. There
are some tiny tabs on the back of there which make it difficult to remove.
Sometimes you'll find that the screw won't actually undo or tighten up because
either the screw is stripped or the lug behind. To fix that you need to grab hold
of the switch at the top and the bottom and actually pull on it with your
finger and thumb whilst undoing the screw. In most cases that will
actually undo the screw. If you can't do that sometimes you may have to get
something behind there and add a little bit of extra leverage but you do have to be
careful not to snap the switch. It's also critical that when you do this the
electricity is isolated. I hope you found this video useful if you have and you
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