The question came to me about how far must the NM cable sheath enter the boxes? I could only find the information located in 334.15(C). Nothing about entering the box sans the conduit. My answer would be, the sheath must extend beyond the clamping device be it a non-metallic box or a metal one. The person calling me was concerned because his boss wants the sheath to be at least 3/4" into the box. There's got to be more important things than this dispute.
Where nonmetallic sheathed cable or multi-conductor Type UF cable is used, the sheath shall extend not less than 6 mm (1/4 in.) inside the box and beyond any cable clamp. In all instances, all permitted wiring methods shall be secured to the boxes.
Last edited by HotLine1; 11/17/1411:04 AM. Reason: Corrected copy booboo
I guess it is because there is more than one kind of cable and they were trying to avoid the mess that was created when they put a cable rule in 320 and referred to it in all the other cable articles. (like accessible attics in 330.23 334.23 etc)