That's an awful big tap. NPT isn't exactly the same as OD thread or root diameter, it's the nominal dimension for the inside of the pipe itself. 5/8" NPT is big - bigger than half inch water pipe. Which would mean adding the wall thickness and threads, too. That makes 3/4 pipe over 1" hole size.
Plus, I'm not sure how available 5/8" NPT is.
NPT- National Pipe Thread Taper- ANSI B1.20.1
FWIW.