How can I bring cable into a junction box with no knockouts?

Question

I need to re-wire a receptacle and hope to do it without replacing the box or cutting open the wall.

I have what looks like a 1995 Bakelite 20.5 cu.in. single gang box with no knockouts, nailed to the stud. The existing 14/2 cable passes through a hole with rough edges punched into the top of the box.

Is there anything to do here besides drill a new hole into the top of the box and fish my new 12/2 cable?

Answer 1

Most bakelite boxes have thin sections of bakelite that are covering the knockouts. Two at the top and two at the bottom.

They are hard to see from the inside, but are in the same place as where that cable comes in.

With a good cleaning with the power off you might see the outlines of the knockouts.

If it was screws holding the box, you might have been able to unscrew from the stud. With nails you are probably looking at replacement of the box.

Answer 2

You can't arbitrarily modify plastic boxes, NEC 110.3. They aren't strong enough to lose structural material in arbitrary places. Metal boxes can handle that, but they already have knockouts.

You need to use the provided cable knockouts, and your box has 4 of them, with one used. Simply do the same as the first cable. Crip659's answer covers this.

Answer 3

To add to what crip659 said...

I have a whole house of these and I've found this to be the most effective way to break them out

1. Flathead screwdriver + hammer. Normally this is a bad idea for your screwdriver, but in this case you need to crack or shatter a hole in the opening. Once you have a hole, stop.
2. Drill it. Once you have a hole, get a decently sized bit (I find 1/4" works well here in both girth and length), put it into the hole you made, and carefully ream the hole out. The thinner knockouts will put up little resistance, but the main box won't let the bit ream it easily.

Answer 4

Usually the bakelite boxes are slightly smaller than new remodel (new work) boxes. I've found that you can break the old bakelite box apart with a punch, screwdriver, dowel, or similar tool thus leaving yourself some wiggle room. Pull your new wire into the Remodel box and insert it back into the wall. You may or may not have to enlarge the old hole to fit the new box. I realize you don't want to put in a new box but fishing a new wire can be a real pain. The plastic remodel box is virtually painless.