Lug Nuts, what’s the story?

MG TDs with steel wheels have two different threads for Lug Nuts and Wheel Studs, depending on the car number.
Up through Car 12284 Wheel Studs and Lug Nuts were 16TPI, Whitworth 7/16 socket
From Car 12285, Wheel Studs and Lug Nuts were 20 TPI, 3/4″ SAE socket
Keep in mind that in the 60 some years since the last TD was made, many cars have had brake drums replaced, and or wheel studs replaced. The best way to be sure of what you have is to use a thread pitch gauge, available at most good hardware stores.

Late TDs and TFs rear axles have Unified Threads instead of BSF, these are the same as ANF (American National Fine or SAE threads). We believe that the switch over to UNF studs occurred at the same time.