My first carrier: some assembly required

[super dave]

I pulled apart my wiring conduit and connectors today as I have to replace all of the pipe as most of them are totally rusted away. everything was going great until i tried a piece of 1/2" pipe in one of the elbows to find out that it is too large of diameter . It looks like the original pipe is about .050 smaller than what today's pipe size is. does anyone know if it is a special size (BSF ??) as the thread size is also smaller than the regular pipe tap as well