Thanks for the replies.
I had considered using 1/2" ENT, but the problem I find, is that if the wires to the existing receptacle outlet are coming vertically down the stud into the box, which is mounted on the opposite side of the metal stud, I can’t really fish up through and then back down the large factory punched hole. So, I usually either must find or drill a hole through the stud below the level of the box and then fish down through an empty KO in the bottom of the nonmetallic box to catch a second horizontal fish tape and bring it up through.
Another issue sometimes is that the Diversibits for sheet metal, only to go up to 3/4", so are not big enough the get 1/2" ENT through or even a snap-in bushing, assuming I'm able get my hand in there to install it. This basically restricts me to using a sleeve of 3/8" flexible metal conduit without fittings, which I always carry on the truck, but I’m not really this is kosher.
Luckily, I don’t run into this very often, but I think what is really needed, is a Diversibit that has a step-drill bit that can make a hole large enough for 1/2" ENT or possibly a standard 1/2" snap-in bushing.
I recently noticed that there is 3/8" ENT available. I suppose this would work, but then I would have to both stock and carry yet another limited use specialty item.
