Using a meyers hub on a 10x10x6 Explosion Proof Enclosure


Electron manager
NE Nebraska
From the Crouse Hinds Catalog sheet for GUE and GUE explosion proof enclosures.

They also have drawings and tables that specify the maximum size and maximum number openings that can be field installed, as well as the locations where these openings are permitted. Additional instructions specify NPT and the depth of the threads.
Never encountered one of those, just boxes with hubs already in them. Depth of the threads makes sense, if you ran a NPT tap all the way through, you would have no taper as the widest part of the tap would leave a straight thread behind if it passed all the way through.