I'm looking to transition NM cable out of 1" EMT using a transition coupling. In the usual case, I read that the right product looks like the photo below. I find many of those for 1/2" EMT (like the photo), but nothing for 1". Is there a common way to do this with 1"? I'm planning to put one or two 10/3 NM cables from a receptacle box, up a cinderblock wall protected by conduit, and then transition them in the ceiling joist area. Many thanks.
I think the connector you are looking for is hard to find because it isn't required.
(B) Protection From Physical Damage. Cable shall be protected from physical damage where necessary by rigid metal conduit, intermediate metal conduit, electrical metallic tubing... Conduit or tubing shall be provided with a bushing or adapter that provides protection from abrasion at the point the cable enters and exits the raceway.
It says "bushing or adapter". Most electricians just use Arlington EMT100 push on bushings for 1" emt. They are cheap and readily available at any electrical supply house.
The obvious answer would be a small box, or a fitting with an access panel that can be used as a box, to contain the splices between the individual wires in conduit and the BNC, with appropriate fitting in each side. Don't forget to make sure safety ground is carried through properly, including grounding the metal conduit and connection box. Note that the box must be accessible for maintenance; you can't bury it behind a wall surface.