Why is it that rigid couplings are not allowed to be used as a transition between connectors? An example would be to connecting emt to flex by using their respective connectors with a rigid coupling in between. Is it a UL listing issue and the connectors are only listed to be used with lockouts? Is conduit grounding continuity not as well maintained without the locknut? Why, then, am I allowed to thread a connector into the hub of a weather-tight box? The finish on those boxes at least appears to provide an inferior connection when compared to a rigid coupling.
There are, of course, single, complete fittings that transition directly from one conduit type to another in a much cleaner fashion. However, due to their limited production, they are much more expensive. When used throughout a project, this adds up and is hard to accept without being given a reason.
