I need to connect a steel junction box on the inside of a building with an outdoor rated disconnect/switch on the outside of the building. The disconnect will be used to power a piece of outdoor equipment and be connected with appropriate cordage to the disconnect.
The wall is 8.5" thick solid concrete. I was planning on drilling a 1" hole through the concrete and connecting the inside box into the back of the outside disconnect using a piece of 3/4" galvanized rigid conduit. I don't, however, have the tools to cut and thread the conduit to length so that the threads can be tightened with conduit locknuts. I asked an electrician if he could do this for me, and he told me to just get a piece of black iron or galvanized plumbing pipe (which I can get pre-threaded in 10-in lengths) and use that instead. Since we are only running THWN wire through this short length of pipe he thought the risk of snagging on the inside of the rough piece of pipe would be minimal. Is this sound advice or should I find another electrician that can cut me a piece of rigid conduit? I thought about using other types of conduit, but I don't see how I could run directly into the back of the disconnect and have room for a conduit connector or clamp unless I make a significantly bigger hole in the concrete. Any advice would be appreciated.
I am also curious as to what standard practice is for caulking sealing outdoor boxes like this when connecting directly through the wall into the back of the box.