I have 2 gang box and I need to expand it to 3 gang. Looked at several videos on U-tube and others, but they all suggest removing the existing box and replacing it with 3 gang plastic. Don't like to use plastic because the threads strip to easily. I thought the industry made it simple to add another gang to the existing older gang-able romex style steel boxes ?
The existing boxes are probably something close to this:
Thanks