Pro Handyman Blog

Cable Clamps For Electrical Junction Boxes

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I was in an attic the other day and looked at a metal electrical junction box. The box had romex cable running into it after the knockouts had been removed. There were no cable clamps or grommets at this area to protect the cable.

If you are using metal junction boxes, you need to use cable clamps. A bag of these will cost only a few dollars, but will hold and protect the cable from damage.  Without a clamp, if there was movement, the sharp metal box could cut into the wire and possibly cause damage. The cable clamp prevents the cable from moving at the box.

The cable has a collar that spins off. The clamp is then placed inside the box so that the threads protrude out of the exterior of the box. Then you can screw the collar onto the threads. This holds the clamp to the box. To hold the cable in the clamp, there are two small screws. Loosen them to spread the clamp open, run the cable through the clamp enough so that you have enough wire to make your connections. This is done with each cable that enters the junction box. The cables are held to the box and the individual wires are connected using the appropriately sized wire nuts.