I cannot understand why electrical boxes have such sharp edges where the cable goes in. The old box I just replaced was made out of that old crumbly brown plastic; it had razor-sharp edges around the hole that gets punched out, that cut gouges in the wire-insulation down to the copper. And the modern plastic boxes have those fold-in “clamps” that do the same thing. – especially when you’re trying to maneuver 12-gauge wires around in it. What gives? I imagine you electricians can address this.

You should be using a bushing made of plastic where the wire enters the box. That will prevent nicking the insulation on the wire. If the insulation is nicked, they can start a fire.

I’ve never been able to find anything like that, and years ago when I was wiring the whole house, that was one of the things that made the experts look at my like I’m nuts. I *am nuts, but not because of that ;+)

I’ve been wiring for nearly 50 years and have never nicked a wire on the edge of a box, nor have I ever found or seen these plastic bushing you are talking about.
If the wire is being nicked, you are probably doing something wrong. On wall boxes the romex goes straight up or down behind the clamp, and if you are trying to go over the top instead you will probably cut the wire in two when you tighten the clamp. The clamps only need to be snugged, you’re not trying to keep the wire from working loose during a A Bomb explosion. Another possibility is trying to cut the wire too short, waste a little wire now and then, its cheaper than a heart attack trying to save a nickle.

The plastic bushings are only used on bx (metal armored) cable, not romex. The way i was taught to do it many yars ago was to wrap the ground wire around the romex and then put it in the strap, that way you insure a goo solid ground.

I read all the responses and I’m inclined to assume you are possibly doing one of two things wrong. First, you are not providing enough length to your wiring. In wiring harness lingo, we call this service loop. Basically, anytime you go around a junction box, or point of entry you have to give the wire a bend or two to allow for strain relief.

If you do this, and you secure the romex to the studs properly you’ll find there will be no stress point where cables enter the box.

The second point which was also mentioned by someone else is the use of crimp/bushing which unfortunately is sold separately and that keeps the cable secure to the box such that when one piece gets pulled out due to destruction of some sort, the wire and box won’t come apart. But as Dale mentioned, this will likely come apart in event of a bomb blast.

I know electricians can sometimes charge a lot of money, but if you look you’ll find one that will give you reasonable rate and by looking over his/her shoulder you’ll learn a lot. Occasionally it pays to let an expert do something, then you can do it yourself the next time.

Wish you success with all your home improvment projects.

This house was already built (not very well); the box I replaced is 25 years old, and the cable is [hopefully] securely attached to the studs, already inside the wall.

For some reason they used 12-gauge cable for these two outlets (maybe I’ll figure out later what else is on this circuit), which is so much stiffer than the 14-gauge. It already had lots of kinks and twists in it, and I could not get the old plastic box off of the wires without the box scraping the insulation (cable coming from both sides inside the wall).

I wrapped some electrical tape around the scrapes, put a new box in, and shoved ’em all back. No fires yet ;+)

I always use the blue plastic boxes available in any store, and I just don’t get why they have the sharp edges on them. I break those tabs off and file off all of the sharp edges. Just hope I didn’t miss any other nicks in the insulation.