simple cable clamp question

[bchee]

I put NM cable into a metal box. How tight are the cable clamps supposed to be? I just screwed it all the way down, but I fear this will damage the cable.
http://www.amazon.com/dp/B000VYIXIQ/?tag=atomicindus08-20

The clamping surface is not a smooth oval, but has 2 ridges which I think are cutting into the cable.

 

[MrMark]

that is a good question. Just tight enough to prevent movement, no more.

 

[falconflyer04]

Do you know what's the code for how many wires you can put in one normal clamp like the one shown above!?

 

[MrMark]

they all will have a listing. You have to check. Some are just one 12/2. The ones I buy are listed for two 12/2, one 12/3, etc.

no one ever checks that but you should.

THat Halex posted is sold by Home Depot and only takes 1 12/2 cable. I don't use them for that reason.