Conduit back boxes 16mm knockouts

[ian.settle1]

Cone cutter?

What the hell has a cone cutter got to do with it?
:28:

 

[Flanders]

To cut a hole the correct size in the back box to fit the imperial conduit is my guess

 

[davesparks]

As above use a conversion socket or use a metal clad surface back box (as it has not got knock outs in the back) if the hole is deep enough of course and drill out 16mm or cone cutter as suggested to get the exact size, You may struggle to drill out a normal metal back box due to the knock outs and you need a good connection for the earth .

What has having knockouts in the back got to do with it?
There's nothing difficult about drilling a standard back box, just fix a bit of plate over the knockouts to give a good connection.

 

[Flanders]

it was Just an idea there are many different ways to do it ,I did not think of your wayI supposed you could just use a metal box lid and bolt it to the back box

 

[ian.settle1]

Don't suppose anybody knows where I can source some 2 gang metal back boxes that are compatible with the old steel conduit systems? Basically need to change a 1 gang to a 2 gang but local wholesalers can't seem to locate anything. The old conduit is about 16mm diameter so knockouts need to fit this.

From what the OP has said he wants to change the back box to a 2 gang which has 20mm but wants it to have 16mm knockouts